Book of Abstracts - IUAC, New Delhi · Book of Abstracts Inter University Accelerator Centre Aruna...

122
Book of Abstracts Inter University Accelerator Centre Aruna Asaf Ali Marg, New Delhi 110067, India

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Book of Abstracts

Inter University Accelerator Centre Aruna Asaf Ali Marg, New Delhi 110067, India

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FUSION14

Book of Abstracts

List of contributorsarranged in alphabetical order

February 19, 2014

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Contents

1 Adhikari S.The study of 12C(α,γ) astrophysical reaction using 12C(6Li,d)and 12C(7Li,t) reaction at 20 MeV and in the framework of thepotential model 1

2 Ahmad ShakebFission barrier in even-even superheavy nuclei 2

3 Ali RahbarStudy of spin distributions and observed side feeding incomplete and incomplete fusion reaction products in theinteraction of 16O with 160Gd 3

4 Ali SabirInvestigation of complete and incomplete fusion in 20Ne+51Vsystem using recoil range measurement 4

5 Aziz Azni AbdulThe effects of double folding cluster model potential onastrophysical reactions 5

6 Basu ChinmayStudy of 13C(α,n) astrophysical reaction using 13C(6Li,d)17Osub-Coulomb transfer reaction 6

7 Behera B.R.To be announced 7

8 Bhattacharya S.To be announced 8

9 Biswas D.C.Energy dependence of optical potential in the near barrierelastic scattering of 11B from 232Th 9

10 Camacho A. GomezWoods-Saxon fusion and direct reaction polarization potentialseffect of breakup on fusion barriers 10

i

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ii CONTENTS

11 Chakrabarti A.To be announced 11

12 Chopra SahilaCompound nucleus formation probability PCN defined within thedynamical cluster-decay model 12

13 Cognata M. LaMeasurement of sub threshold resonance contributions to fusionreactions: The case of the 13C(α,n)16O astrophysical neutronsource 13

14 Corradi L.Transfer reaction studies in inverse kinematics with themagnetic spectrometer PRISMA 14

15 Courtin S.Exploring the influence of transfer channels on fusionreactions: the case of 40Ca+58,64Ni 15

16 Derkx X.Superheavy element research with the gas-filled recoilseparator TASCA at GSI 16

17 Dutt SunilComplete and incomplete fusion reaction in the interaction of16O+55Mn system below 7 MeV/A: Measurement and analysis ofexcitation functions 17

18 Eudes P.A unified homographic law for fusion excitation functions abovethe barrier 18

19 Fang Y.D.Fusion and 1n stripping reactions in the 9Be+169Tm, 181Ta and187Re systems 19

20 Gan Z.G.A new neutron-deficient isotope 205Ac on gas-filled separatorSHANS 20

21 Ghosh T.K.Shell effects in fission fragment mass distribution 21

22 Godre Subodh S.Classical molecular dynamics simulation of weakly-boundprojectile heavy-ior reactions 22

23 Godre Subodh S.Three-stage classical molecular dynamics model for simulationof heavy-ion fusion reactions 23

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CONTENTS iii

24 Goyal SaviEffect of shell closure on neutron multiplicity of fissioningsystems 220,222,224Th nuclei 24

25 Goyal SaviInfluence of deformation of projectile on the neutronmultiplicity for the 28Si+204,206,208Pb systems 25

26 Gupta Y.K.Revisiting the symmetric reactions for synthesis of super heavynuclei of Z ≥ 120 26

27 Hagino K.To be announced 27

28 Hemalatha M.Elastic scattering of halo nucleus 11Li in the vicinity ofCoulomb barrier 28

29 Hinde D.J.Mapping quasifission characteristics in heavy element formationreactions 29

30 Jha V.Understanding reaction mechanism of pair transfer using twoneutron transfer in 18O+206Pb system 30

31 Jia H.M.Fusion of 32S+90,96Zr, 16O+76Ge and 18O+74Ge: The possible effectof positive Qxn-value neutron transfer on sub-barrierfusion 31

32 Kanwar ShefaliStudy of complete fusion in 16O+24,26Mg reaction 32

33 Karim AfaqueA study of finite temperature effect in pairing correlationsin nuclei 33

34 Karpov AlexanderRole of neutron rearrangement channels in sub-barrier fusion 34

35 Kaur GurpreetStudy of nuclear structure effect on fusion through barrierdistribution for the system 28Si+154Sm 35

36 Kaur ManinderSpin distribution as a probe to investigate the dynamicaleffects in fusion reactions 36

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iv CONTENTS

37 Kumar AjayStudy of angular momentum hindrance in heavy ion fusionreactions 37

38 Kumar HarishInvestigation of projectile break-up process in 12C+175Lu systemand mass-asymmetry effect on incomplete fusion 38

39 Kumari AnjuA study of fusion of 8B+58Ni system in near barrier energyregion 39

40 Kumari RajA new technique to determine fusion barrier heights usingproximity potentials 40

41 Kumar KamalLow energy incomplete fusion: Observation of a significantincomplete fusion fraction at ` < `crit 41

42 Kumar SanjeevQuantum molecular dynamical model for the incident energy onand above 50 MeV/nucleon 42

43 Kumar SureshA new way to study the rotational states built on the HoyleState 43

44 Li G.S.Reaction mechanisms in the 9Be+89Y system 44

45 Lin C.J.Optical model potentials for 6He+209Bi extracted from208Pb(7Li,6He)209Bi reaction 45

46 Luong D.H.Breakup, α-particles production and fusion suppression inreactions with 7Li 46

47 Mahajan RuchiStatistical model calculations for evaporation residue andfission cross-section for 210Po nuclei 47

48 Mahata K.Fission barrier of 210Po 48

49 Mazzocco M.Reaction dynamics studies for the system 7Be+58Ni 49

50 Montagnoli G.Fusion of 28Si+28Si near and below the barrier 50

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CONTENTS v

51 Montanari D.Transfer reactions in the 60Ni+116Sn superfluid system atsub-Coulomb energies 51

52 Morita K.To be announced 52

53 Mukul IshSpin gated GDR widths at moderate temperatures 53

54 Navin A.To be announced 54

55 Nayak B.K.To be announced 55

56 Nishio K.To be announced 56

57 NiytiStudy of α-decay of 270Hs using the dynamical cluster-decaymodel 57

58 Palmerini S.The effect of the recent 17O(p,α)14N and 18O(p,α)15N fusioncross section measurements in the nucleosynthesis of AGBstars 58

59 Pandey BhawnaReaction mechanisms in the 6Li+52Cr system 59

60 Parkar V.V.Elastic scattering and fusion with 9Be projectile 60

61 Parkar V.V.Fusion of 7Li with 124Sn from online and offline gamma raymeasurement technique 61

62 Patel D.Investigation of transfer in triggering breakup in the reactionof 6Li with 208Pb, 209Bi 62

63 Phookan C.K.A model for explanation of fusion suppression using classicaltrajectory method 63

64 Piot J.To be announced 64

65 Pizzone R.G.Trojan Horse particle invariance in fusion reactions 65

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vi CONTENTS

66 Pradhan M.K.Effect of breakup couplings on fusion for 6,7Li+24Mg systems 66

67 Rana T.K.Fragment emission studies in low energy light ion reactions 67

68 Rathi SarlaAverage angular momentum for fusion of 7Li+165Ho 68

69 Rath P.K.Breakup phenomena study in 7Li+208Pb reaction using 8PLP 69

70 Ray A.Quasifission and fission timescale: zeptosecond versusattosecond 70

71 Roy B.J.Multinucleon transfer study in 58Ni,56Fe(12C,X); X:11C, 11,10B,10,9,7Be, 8Begs, and 7,6Li at E(12C)=45 and 60 MeV 71

72 Samarin V.Coupling with two-center neutron states and two-surfacecollective excitations at fusion reactions in vicinity ofCoulomb barrier 72

73 Samarin V.Time-dependent quantum models of near barrier nucleon transferreaction dynamics 73

74 Sawhney GudveenDeformation and orientation effects in heavy-particleradioactivity of Z = 115 74

75 Scamps GuillaumeEffect of pairing on transfer and fusion reactions 75

76 Sekizawa KazuyukiTime-dependent Hartree-Fock calculation for multinucleontransfer processes 76

77 Shaikh Md. MoinFusion excitation function measurement for 6Li+64Ni at near thebarrier energies 77

78 Sharma M.K.Fission dynamics of 240Cf∗ formed in 34,36S induced reaction 78

79 Sharma PriyaStatistical model calculation for evaporation residue andfission cross section for 48Ti+122Sn system 79

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CONTENTS vii

80 Sharma Vijay R.Incomplete fusion reactions in 16O+159Tb system: Spindistribution measurements 80

81 Sharma Vijay R.Incomplete fusion systematics with Universal Fusion Functionmodel and α-Q value 81

82 Shrivastava A.Emergence of fusion hindrance for asymmetric system at extremesub barrier energies 82

83 Simenel C.Microscopic study of the effect of collective vibrations onlow-energy fusion 83

84 Singh BirBikramHeavy ion collision dynamics of 10,11B+10,11B reactions 84

85 Singh BirBikramDynamical decay of 32S∗ and 31P∗ formed in 20Ne+12C and 19F+12Creactions, respectively, at E∗

CN = 60 MeV 85

86 Singh Devendra P.Observation of in-complete fusion at low angular momentumvalues 86

87 Singh D.Effect of the target deformation on incomplete fusiondynamics 87

88 Singh VarinderjitFission excitation function for 19F+194,196,198Pt at near andabove barrier energies 88

89 Singh VarinderjitSpin distribution measurement of 64Ni+100Mo at near and abovebarrier energies 89

90 Solovyev A.S.Microscopic calculation of astrophysical S-factor and branchingratio of the reaction 3H(α,γ)7Li 90

91 Srivastava VishalStructure of 26Al studied by one-nucleon transfer reaction27Al(d,t) 91

92 Stefanini A.M.Transfer couplings and hindrance far below the barrier in thefusion of 40Ca+96Zr 92

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viii CONTENTS

93 Stefanini A.M.Fusion hindrance and quadrupole collectivity in collisions ofA'50 nuclei 93

94 Stevenson P.D.Role of the Skyrme tensor terms in fusion thresholds 94

95 Sugathan P.Fusion-fission studies around Coulomb barrier energies usingIUAC facilities 95

96 Szilner S.Probing nucleon-nucleon correlations via heavy ion transferreactions 96

97 Thakur MeenuStatistical model calculations of pre-scission neutronmultiplicity for the heavy ion induced fusion-fission reactionswith actinide target 232Th 97

98 Wakhle A.Comparison of quasifission mass angle distributions fromexperiment and TDHF calculations 98

99 Washiyama KouheiFusion and quasi-fission in heavy systems with the microscopictime-dependent energy density functional theory 99

100Watanabe Y.X.Study of multinucleon transfer reactions of 136Xe+198Pt forproduction of exotic nuclei 100

101Williams E.The evolution of signatures of quasifission in reactionsforming Curium 101

102Wolski R.An alternative explanation of heavy ions sub-barrier fusionenhancement 102

103Yadav AbhishekLow energy in-complete fusion and its relevance to synthesisof superheavy elements 103

104Yeremin A.First experimental tests of the kinematic separator SHELS(Separator for Heavy ELement Spectroscopy) 104

105Zagrebaev V.I.Synthesis of superheavy nuclei: nearest and distantopportunities 105

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CONTENTS ix

106Zemlyanoy S.GALS - setup for production and study of heavy neutron richnuclei 106

107Zhou Shan-GuiLangevin dynamics in nuclear fusion emerging from quantummolecular dynamics simulations 107

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x CONTENTS

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FUSION14

The study of 12C(α,γ) astrophysical reaction using 12C(6Li,d) and 12C(7Li,t) reaction at20 MeV and in the framework of the potential model

S. Adhikari,1, ∗ C. Basu,1 P. Sugathan,2 A. Jhingan,2 B.R. Behera,3 N.Saneesh,2 R. Dubey,2 G. Kaur,3 M. Thakur,3 R. Sharma,3 and A.K. Mitra1

1Nuclear Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhan nagar, Kolkata-700064, India2Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067, India

3Physics Department, Panjab University, Chandigarh-160014, India

The 12C(α,γ) fusion (capture) cross-section at 300 keVdetermines the ratio of the abundance of 16O to 12C inhelium burning stars [1]. A direct measurement of thecross-section is very low at such low energy and so ex-trapolation of cross-section measured at higher energyis carried out. The extrapolation depends on the al-pha width of two subthreshold states of 16O at 6.92 (2+)and 7.12 (1+) MeV. This is because the capture at theGamow window is expected to occur through the tail ofthe wavefunction of these two resonances. The magni-tude of this tail is termed as the Asymptotic Normaliza-tion constant (ANC). The determination of the ANC orthe alpha spectroscopic factor (Sα) of the 16O states arethus important for the extrapolation. The reduced al-pha width of the 16O states (that are related to Sα) havebeen determined mainly from two alpha transfer reac-tions viz. 12C(6Li,d) and 12C(7Li,t) [2, 3] at differentincident energies. A comparison of the measured angulardistribution with respect to an appropriate calculationyields the spectroscopic factor. The extracted Sα de-pends critically on the model used to analyse the data.In most earlier calculations, the Finite Range DistortedWave Born Approximation (FRDWBA) has been usedassuming a direct transfer process. However, 6,7Li beingloosely bound are likely to breakup up and can affect thetransfer process and thereby the Sα. This can be inves-tigated in the framework of the Continuum DiscretizedCoupled Channel (CDCC-CRC) theory. In two separateexperiments angular distributions were measured for the12C(6,7Li,d/t) reactions at 20 MeV populating the dis-crete states of 16O.

The measurements were carried out using the GPSCfacility at IUAC Pelletron, New Delhi. The beam energyfor both the reactions were kept at 20 MeV. The CDCC-CRC analysis [2] using the code FRESCO [4] shows aprominent contribution of breakup effects on the trans-fer process particularly for the ground and other boundstates of 16O and hence on the extracted alpha spec-troscopic amplitudes. A strong coupling between thedifferent states of the 16O were also observed from the

calculations. The astrophysical S-factor for E2 capturewas calculated at 300 keV with the extracted Sα usinga potential model for capture reaction. The 12C(7Li,t)reaction is interesting to study in this context as 7Li hasa higher α breakup threshold compared to 6Li and thebreakup effects may be less. In fig.1 we show the tritonangular distributions measured from the 12C(7Li,t) pop-ulating the ground state of 16O. In the potential modelfor E2 capture both the ground and 6.92 MeV state Sαare important.

The FRDWBA calculations are shown by red lines andthe CRC calcultions by blue lines in fig.1 . In the formerwhereas a direct transfer is assumed the later takes intoaccount the coupling between 16O states. The underpre-dictions at backward angles may be a result of Compoundnuclear emissions or due to the breakup transfer processand needs further investigationsfor the proper evaluationof Sα.

FIG. 1: Comparison of CRC(blue) and DWBA (red) calcula-tions with the data for the 16O ground state.

∗corresponding author: [email protected]

[1] C. E. Rolfs and W. S. Rodeney, Cauldrons in the Cosmos,The University of Chicago Press, Chicago and London.

[2] S. Adhikari et al, AIP Conference Proceedings 1491, 359(2012).

[3] N. Oulebsir et al, Phys. Rev. C 85, 035804 (2012).[4] I. J. Thompson, Comp. Phys. Rep. 7, 167 (1988).

1

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FUSION14

Fission Barrier in Even-Even Superheavy Nuclei

Shakeb Ahmad,1, ∗ Afaque Karim,1 M. Bhuyan,2, 3 and S. K. Patra3

1Department of Physics, Aligarh Muslim University, Aligarh-202 002, INDIA2School of Physics, Sambalpur University, Jyotivihar, Sambalpur-768 019, INDIA

3Institute of Physics, Sachivalaya Marg, Bhubaneswar-751 005, INDIA

Based on the discovery of newly discovered superheavyelements, physicists concluded that these results providean evidence for the existence of island of stability of su-perheavy nuclei, and the next magic number, if any. Inorder to study the stability of superheavy nuclei againstthe spontaneous fission is to investigate systematically,the properties of fission barriers, because, the fission bar-riers is one of the fundamental characteristics of super-heavy nuclei, as these superheavy nuclei decay sponta-neously through fission, and therefore their stability canbe investigated essentially by the size and shape of thefission barrier. In recent years, many investigations havebeen devoted to a relativistic description of the groundstate properties of superheavy nuclei. It has been foundin recent relativistic mean field (RMF) calculations thatmany superheavy nuclei may have superdeformed groundstate [1, 2]. In other words, the second minimum of thepotential (at the quadrapole deformation β2) is obtainedto be lower than the first one for these nuclei.

In this communication, we study the ground stateproperties of even-even superheavy nuclei (Z=112-120).We put emphasis on the role of deformation on the struc-ture of superheavy nuclei. We will address the problem of

superdeformed ground state these nuclei, their deforma-tion energy curves and the potential energy surface. Wehave used both the non-relativistic Skyrme-Hartree-FockSHF [3] and the deformed Relativistic Mean Field RMF[4] models in a constrained calculation. We will be pre-senting the systematic investigations of fission barriers ineven-even superheavy nuclei with charge number Z=112-120 within relativistic mean field theory including the tri-axial shapes and octupole shapes with axial symmetry.We have used the improved version of NL3 parameter set(NL3*), standard NL3, SkI4 and SLy4 parameter sets forour calculations. The pairing correlations are treated us-ing the BCS approximation using the seniority pairingforces adjusted to emprical values of the gap parameters.We will be presenting the investigations for potential en-ergy surface (PES), and the deformation energy curvesfor several isotopes with charge number Z=112, 114, 116,118 and 120 nuclei obtained with the NL3* parametriza-tion of the RMF Lagrangian. The results will be for thecase of axial solution with reflection symmetry, triaxialsoultions with reflection symmetry, and octupole defor-mation solutions with axial symmetry.

∗corresponding author:[email protected]; Permanent ad-dress:AMU, Aligarh, India.

[1] Z. Ren, H. Toki, Nucl. Phys. A689, 691 (2001).[2] Z. Ren, Phys. Rev. C65, 051304 (R) (2002).[3] E. Chabanat, P. Bonche, P. Hansel, J. Meyer, and R. Scha-

effer, Nucl. Phys. A627, 710 (1997).[4] J. Boguta, A. R. Bodmer, Nucl. Phys. A292, 413 (1977).

2

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FUSION14

Study of spin distributions and observed side feeding in complete and incomplete

fusion reaction products in the interaction of 16O with 160Gd

Rahbar Ali,1, ∗ D. Singh,2 M. Afzal Ansari,3 Rakesh Kumar,4 M. K. Sharma,3 Unnati,3 B. P.

Singh,3 P. D. Shidling,5 Dinesh Negi,6 S. Muralithar,4 R. P. Singh,4 and R. K. Bhowmik4

1Department of Physics, G. F. (P. G.) College, Shahjahanpur - 242 001, INDIA2Centre for Applied Physics, Central University of Jharkhand, Ranchi - 835 205, INDIA

3Department of Physics, Aligarh Muslim University, Aligarh - 202 002, INDIA4Inter-University Accelerator Centre, New Delhi - 110 067, INDIA

5Cyclotron Institute, Texas A&M University, College Station, Texas 77843-3366, USA6NP-Lab, iThemba LABS, NR Foundation, P.O.B722, Somerset West 7129, South Africa

Spin distribution of evaporation residues (ERs) pop-ulated via complete fusion (CF) and incomplete fusion(ICF) like xn, α/2α-xn and αp/2αp-xn channels havebeen observed in the interaction of 16O with 160Gd at ≈5.6 MeV/A energy . The particle-γ coincidence experi-ment has been performed using Charged Particle Detec-tor Array (CPDA) and Gamma Detector Array (GDA)at IUAC, New Delhi. The measured spin distributionshows constant yield up to 9 for direct α/αp-xn and11 for 2α/2αp-xn (both associated with ICF), there af-ter yield successively decreases exponentially with highspin states, while spin at half yield (i.e. mean input an-gular momentum) for all CF channels comes out to be 7.An attempt has been made to extract the side-feeding

pattern from the spin distribution for all CF and ICFchannels like xn, α/2α-xn and αp/2αp-xn channels. Ithas been observed that CF products are strongly fed overbroad spin range, while low partial waves are stronglyhindered in the fast α-emission channel (associated withICF) in the forward direction and no side-feeding takesplace in the low observed spin.These features of side feed-ing in ICF reaction products are consistent with Inamuraet al., [1] and Singh et al.,[2]. It has also been observedthat mean input angular momentum for direct α-emittingchannels have been found to be relatively higher thanevaporation α-emitting channels and increases with di-rect α-multiplicity in forward direction and hence leadto peripheral interaction.

∗corresponding author: [email protected]; Permanent ad-dress:Department of Physics, G. F. (P. G.) College, Shahjahanpur-

242 001, INDIA

[1] T. Inamura et al., Phys. Lett. B 68, 51 (1977).[2] D. Singh et al., Phys. Rev. C 81, 027602 (2010);

3

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FUSION14

Investigation of complete and incomplete fusion in 20Ne+51V system using recoil rangemeasurement

Sabir Ali,1, ∗ Tauseef Ahmad,1 Kamal Kumar,1 I. A. Rizvi,1 AvinashAgarwal,2 S. S. Ghugre,3 A. K. Sinha,3 and A. K. Chaubey4

1Department of Physics, Aligarh Muslim University, Aligarh 202002, India2Department of Physics, Bareilly College, Bareilly 243005, India

3 UGC-DAE Consortium for Scientific Research, Kolkata 700098, India4Department of Physics, Addis Ababa University, P.O.Box 1176, Addis Ababa,Ethiopia

The recoil range distribution (RRD) has been usedto study the complete and incomplete fusion reactionsfor the 20Ne + 51V system. The RRD of the evapora-tion residues formed through different possible channelshas been measured using the recoil catcher technique fol-lowed by gamma spectrometry. The linear momentumtransfers inferred from these RRDs were used to identifythe evaporation residues formed by complete and incom-plete fusion mechanism. The experimentally measuredrecoil range of the observed residues was compared withthe theoretical values obtained using the code SRIM [1].The experimentally measured reaction cross section ofthe observed residues were compared with the values ob-tained from the statistical model code PACE4 [2]. Thereaction cross sections of the pxn channels were found tobe in good agreement with the PACE4 values where as

that of α emitting channels shows an enhancement overthe predicted PACE4 values. This enhancement of ex-perimentally measured reaction cross sections over thePACE4 values suggest the formation of α emitting chan-nel residues through incomplete fusion process. Angularmomentum distribution has been derived from the ob-served reaction cross section using the sharp cut-off ap-proximation. This angular momentum distribution wasfurther compared with the angular momentum distribu-tion obtained using couple channel calculation performedusing the code CCFULL [3]. In CCFULL calculation, thecoupling effect of both projectile and target were takeninto account. The derived angular momentum distribu-tion was found to be in good agreement with the CC-FULL calculation.

∗Sabir Ali: [email protected]

[1] J. F. Ziegler, SRIM-2006,The StoppingPower and Range of Ions in Matter[http://www.srim.org/SRIM/SRIMLEGL.htm].

[2] A. Gavron, Phys. Rev. C 21, 230 (1980).

[3] K. Hagino, N. Rowley and A. T. Kruppa, Comput. Phys.Commun. 123, 143 (1999).

4

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FUSION14

The effects of Double Folding Cluster Model Potential on astrophysical reactions

Azni Abdul Aziz,1, ∗ Hasan Abu Kassim,1 and Muhammad Zamrun F.21Department of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia

2Jurusan Fisika FMIPA, Universitas Haluoleo Kendari, Sulawesi Tenggara, J3232 Indonesia

The Double Folding Cluster Model Potential is con-structed using the α-cluster structure of nuclei. It canbe derived by folding an α − α interaction with densitydistributions of α-clusters inside projectile and target nu-clei. This potential has been successfully tested on elastic

scattering data of selected nuclei. In this work, we are in-terested to apply this potential to explain the fusion crosssection and investigate the implications on astrophysicalaspects.

∗Permanent address:Kulliyah of Science, International Islamic Uni-versity Malaysia, 25200 Kuantan, Malaysia

5

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FUSION14

Study of 13C(α,n) astrophysical reaction using 13C(6Li,d)17Osub-Coulomb transfer reaction

Chinmay Basu1, ∗ and Sucheta Adhikari1

1Nuclear Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhan nagar, Kolkata-700064, India

The rate of the 13C(α,n) fusion reaction at around190 keV determines the s-process nucleosynthesis in AGBstars. The direct measurement of this reaction has beendone down to around 270 keV [1]. The small reactioncross-section at this low energy prohibits a determina-tion of the rate with small uncertainty. The extrapo-lation of the astrophysical S-factor from the region ofmeasured energies to the Gamow window is influencedby the 1/2+ subthreshold resonance in 17O, 3 keV belowthe α-13C threshold (6.359 MeV). The alpha width of thisresonance affects the extrapolation. This width can bedetermined from the alpha spectroscopic factor (Sα ex-tracted from transfer angular distribution measurementsA few studies using 13C(6Li,d)17O or the inverse reactionhave been carried out recently [2, 3]. In these studies thealpha spectroscopic factor or the Asymptotic Normaliza-tion Constant (ANC) was determined from a compari-son of the measured angular distributions with the calcu-lated cross-sections. The calculations in all these studieswere carried out in the framework of the Finite RangeDistorted Wave Born Approximation (FRDWBA). How-ever, for loosely bound projectiles, breakup effects on thetransfer process can be quite significant and influence theextracted values of Sα and ANC. In this work, we studythe effect of the breakup process on alpha transfer in theframework of the Continuum Discretized Coupled Reac-tion Channel (CDCC-CRC) theory [4]. The extractedalpha spectroscopic factors are different from those usingDWBA methods and can influence the value of the cal-culated astrophysical S-factor of the 13C(α,n) reaction.The method adopted in this work is a CDCC-CRC anal-ysis of the 6Li(13C,d) angular distribution data measuredby Johnson et al at sub Coulomb energies [2]. The otheravailable angular distribution data are all at above bar-rier energies.

At sub Coulomb energy the calculations are expectedto be independent of the uncertain nuclear potentials thatcan lead to a large variation in the value of the spec-troscopic factor. In the CDCC-CRC framework we as-sume a two body α+d and α+13C structure for 6Li and17O respectively. The 6Li continuum model space abovethe threshold contains a continuum with three resonantstates. The widths of these resonant states are obtaindby adjusting the α+d binding potential and studying

the phase shifts. Besides the real binding potentials,optical potentials for the entrance, exit and core-core(d+13C) channel were adopted from [2]. A comparisonof our CDCC-CRC calculations with the FRDWBA cal-culations are shown in fig.1. The spectroscopic factorobtained from the CDCC-CRC calculations are 0.22 andis about 45% less than the DWBA results. However, thepresent calculations can be further improved if the an-gular distribution populating the other states of 17O canbe measured as has been done by Kubono et al [3] atabove barrier energies. A determination of the spectro-scopic amplitudes of these states would then be possible.This is because the states that strongly couple with the6.356 MeV state may influence it’s spectroscopic ampli-tude. However, the large difference in Sα extracted fromthe present calculations with the DWBA results showsthat the proper choice of the theoratical model is criticalfor the correct evaluation of the S-factor for the 13C(α,n)reaction at 190 keV.

The relevant figure(s) should be referred to as Fig. 1.

FIG. 1: Comparison of FRDWA (blue) and CDCC-CRC(red) calculations fitted to the sub Coulomb deuteron angulardistribution data for the 6Li(13C,d) reaction at E(13C)=8.0MeV.

∗corresponding author: [email protected]

[1] M. Heil et al, Phys. Rev. C 78, 025803 (2008).[2] E. D. Johnson et al, Phys. Rev. Lett. 97, 192701 (2006).[3] S. Kubono et al, Phys. Rev. Lett. 90, 062501 (2003).

[4] I. J. Thompson, Comp. Phys. Rep. 7, 167 (1988).

6

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FUSION14

To be announced

B.R. Behera1

1Panjab University, India

7

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FUSION14

To be announced

S. Bhattacharya1

1VECC, India

8

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FUSION14

Energy dependence of optical potential in the near barrier elastic scattering of 11Bfrom 232Th

Shradha Dubey,1, 2 S. Mukherjee,1 D. Patel,1 Y. K. Gupta,2 L. S. Danu,2 B. N. Joshi,2

G. K. Prajapati,2 S. Mukhopadhyay,2 B. V. John,2 B. K. Nayak,2 and D. C. Biswas2, ∗

1Physics Department, Faculty of Science, M.S.University of Baroda, Vadodara-390002, India2Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400085, India

The study of elastic scattering angular distributionsdetermine parameters of the real and imaginary parts ofthe nuclear interaction potential. From systematic anal-ysis of elastic scattering measurements involving tightlybound nuclei, the so called threshold anomaly (TA) hasbeen observed in a number of systems [1]. This has beenunderstood in terms of couplings of elastic channel to thedirect reaction channels that generate an additional at-tractive real dynamic polarization potential. The studyof the TA is important to investigate the influence ofthe breakup and other reaction mechanisms on the elas-tic and fusion channels [2, 3]. In the present work, we

FIG. 1: Experimental elastic scattering cross section normal-ized to the Rutherford cross section as a function of θc.m. for11B + 232Th system.

have studied the elastic scattering cross section for 11B+ 232Th system through very precise and complete an-

gular distribution measurements at energies around theCoulomb barrier. The total reaction cross sections forthis system have also been derived in order to investigatethe role of projectile structure on the total reaction crosssection. The experiment was performed at the 14UD

TABLE I: Optical model parameters obtained by fitting theexperimental elastic differential cross section data using theECIS code for 11B + 232Th system.

Elab(MeV) Vr(MeV) Vi(MeV) χ2

nσR(mb)

52 278.2 2.32 0.32 9.65

53 173.8 17.52 0.64 29.81

54 188.8 36.64 1.21 89.74

55 156.5 31.81 4.04 105.3

56 146.6 59.27 3.52 216.1

57 127.5 66.46 4.70 279.6

59 141.0 68.83 5.00 432.2

61 86.13 103.9 11.2 601.4

65 62.76 127.6 9.12 885.7

BARC-TIFR Pelletron facility at Mumbai using beamof 11B. Four ∆E-E silicon surrface barrier detector tele-scopes used to mesaure the elastic scattered particles inthe anglular range 35 to 170. The optical model anal-ysis of the elastic scattering data were performed usingthe ECIS code [4]. In the fitting procedure the real andimaginary radius parameters (ro = 1.06 fm) and diffuse-ness parameters (av and aw = 0.71 fm ) were kept fixedand only the depth of real and imaginary potential pa-rameters (Vr and Vi) were varied to obtain the best-fitof the experimental data for all energies. Over all, verygood fits to the experimental data were obtained at allenergies as shown in Fig. 1.The values of the potentialparameters for the best fit and the total reaction crosssection are shown in Table-I. More detailed analysis is inprogress and the results will be presented. This work ispartially supported by a research project being financedby UGC-DAE-CSR, Kolkata.∗corresponding author:[email protected]

[1] G. R. Satchler, Phys. Rep. 199, 147 (1991).[2] J. Lubian et al., Nucl. A 791, 24 (2007).[3] N. N. Deshmukh et al., Phys. Rev. C 83, 024607 (2011).

[4] J. Raynal, Phys. Rev. C 23, 2571 (1981).

9

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FUSION14

Woods-Saxon Fusion and Direct Reaction Polarization Potentials

Effect of Breakup on fusion barriers

A. Gomez Camacho1, ∗ and E.F. Aguilera1, P. R. S. Gomes2, J. Lubian21Instituto Nacional de Investigaciones Nucleares, Departamento del Acelerador,

Apartado Postal 18-1027, C.P. 11801, Mexico D.F.2Instituto de Fisica, Universidade Federal Fluminense,

Avenida Litoranea s/n, Gragoata. Niteroi RJ, cep 24210-340, Brazil

Nuclear reactions involving weakly bound and haloprojectiles have been the source of extensive investiga-tions in recent years[1]. Since this type of projectileshas low threshold energies, they can split into differentfragments even at low collision energies. Hence, largebreakup and transfer yields are appreciable at energiesaround and below the Coulomb barrier. Similarly, dueto the large breakup cross sections, other nuclear reac-tion mechanisms like elastic scattering and fusion, arestrongly affected by this reaction process[1—3]. In recentworks, the effect of breakup on fusion has been studiedby determining the dynamical polarization potential thatarises from couplings between the incident elastic channelto different reaction channels. This polarization poten-tial () has been calculated by a simultaneous fittingto elastic and fusion cross section data for various weaklybound systems[4—9]. In this contribution, a brief descrip-tion of the results obtained in recent years is presented.The basic idea is to split () into fusion () anddirect reaction () parts, where the former is thepolarization potential emerging from elastic-fusion chan-nel couplings and the latter from couplings to elastic-direct reaction ones. Besides, the real and imaginaryparts of () and (), namely , and, respectively, are assumed to have Woods-Saxon shapes whose parameters are calculated by a 2-analysis of the elastic and fusion data. It is found that,

the calculated energy dependence of the real and imag-inary parts of the fusion polarization potential and not only are linked by the dispersion relation, butalso show a behavior consistent with the usual Thresh-old Anomaly. That is, the incident flux that is absorbedinto the fusion channel, represented by () decreasesas the energy also diminishes below the Coulomb barrier . On the other hand, the associated virtual poten-tial , that arises from couplings between the incidentelastic channel and the fusion ones, becomes attractivewith a bell-shape energy dependence centered around thebarrier . As a matter of fact, an important result ofthe present analysis is that, for all the systems studied,the calculated imaginary absorption potential (),which is the potential that accounts for the flux thatis absorbed into direct reactions (basically breakup forweakly bound systems), does not decrease around andbelow the barrier, as does (). Conversely, the de-termined dynamic direct reaction real polarization poten-tial () becomes repulsive around the barrier energy.Therefore, () has the important effect of increasingthe fusion barrier and thus hinders fusion. This particu-lar energy dependent behavior of () and ()is linked by the dispersion relation. Finally, the effect onfusion due to (),() is investigated. First, theseparate effect of either () and() is studied,then the combined effect is calculated.∗corresponding author: [email protected]

[1] Canto L F, Gomes P R S, Donangelo R, Hussein M S 2006

Phys. Rep. 424 1.

[2] Bertulani C A, Hussein M S and Munzenberg G, 2001

Physics of Radioactive Beams (Nova Science, New York)

[3] Bertulani C A, Canto L F, Hussein M S, 1993 Phys. Rep.

226 281

[4] Udagawa T, Tamura T, 1984 Phys. Rev. C 29 1922

[5] Udagawa T, Kim B T, Tamura T, 1985 Phys. Rev. C 32

124

[6] Gomez Camacho A, Gomes P R S, Lubian J, Padron I,

2008 Phys. Rev. C 77 054606

[7] Gomes P R S et al., 2009 Nucl. Phys. A 828 233

[8] Gomez Camacho A, Aguilera E F, Gomes P R S, Lubian

J, 2011 Phys. Rev. C 84 034615

[9] Gomez Camacho A, Gomes P R S, Lubian J, 2010 Phys.

Rev. C 82 067601

10

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FUSION14

To be announced

A. Chakrabarti11VECC, India

11

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FUSION14

Compound nucleus formation probability PCN defined within the dynamicalcluster-decay model

Sahila Chopra,1, ∗ Arshdeep Kaur,1 and Raj K. Gupta1

1Department of Physics, Panjab University, Chandigarh-160014, India.

The compound nucleus (CN) model of N. Bohr [1] as-sumes its formation probability PCN=1 for complete fu-sion, and treates its decay statistically. However, non-compound nucleus (nCN) decays (PCN <1) also occur.We extend this idea here to the Dynamical Cluster-decayModel (DCM) of Gupta and collaborators [2–4] for thecase of non-zero nCN contribution.

The DCM is a non-statistical description of decay ofCN emitting multiple light particles (A≤4, Z≤2), calledevaporation residue (ER), and fusion-fission (ff) frag-ments (including intermediate mass fragments, IMFs).Also, several nCN processes, like quasi-fission (qf), deep-inelastic collisions, incomplete fusion, etc., contribute,such that the total decay/ formation cross-section is

σTotal = σER + σff + σnCN = σCN + σnCN . (1)

If σnCN were not measured explicitly, it can be estimatedempirically from the calculated and measured σCN , as

σnCN = σExpt.CN − σCal.

CN . (2)

Then, PCN is defined as

PCN = σCN/σTotal (3)

In DCM, σ for each fragmentation (A1, A2) is definedin terms of collective coordinates of mass asymmetry η =(A1 − A2)/(A1 + A2) and relative separation R, using ℓpartial waves, as

σ =π

k2

ℓmax∑ℓ=0

(2ℓ + 1)P0P ; k =

√2µEc.m.

~2(4)

Here P0 is formation probabilty, given as the solution ofstationary Schrodinger equation in η, and penetrabilityP , the WKB integral representing R coordinate. Thesame equation is used for σnCN , calculated as the quasi-fission process, since incoming nuclei keep their identity,

and hence P0=1, and P calculated for incoming channel.Note that, in the language of coupled channel calcula-tions, σTotal = σcapture, if calculated as “barrier cross-ing” [5]. In DCM, however, there is additional factor P0.

Fig. 1 shows the variation of PCN with the fissility pa-rameter χ = (Z2/A)/48 for CN 196Pt∗, 202Pb∗, 246Bk∗and 286112∗, based on the reactions given in the bodyof figure, at various excitation energies E∗ [6–9], forming

0.4 0.5 0.6 0.7 0.8 0.910-3

10-2

10-1

100

1:64Ni+132Sn 196Pt*

2:48Ca+154Sn 202Pb*

3:11B+235U 246Bk*

4:48Ca+238U 286112*

E*=(22-55) MeV

E*=(56-88) MeV

P CN

(Z2/A)/48

1 2 3 4

FIG. 1: Variation of PCN with fissility parameter.

two energy ranges E∗=22-55 and 56-88 MeV. We noticein Fig. 1 that for the high energy range (E∗=56-88 MeV),PCN ≈1 for all the systems with χ lying between 0.6 and0.8. On the other hand, for the low energy range (E∗=22-55 MeV), PCN varies from ∼1 to zero as χ increases from0.6-0.9. Thus, for CN having χ=0.6-0.8, the PCN=1 butfor the heavy system, like 286112 with higher χ (=0.914),the PCN <<1, indicating the presence of large nCN ef-fects. Interestingly, exactly similar behaviour is observedin other published works [5].

∗corresponding author : [email protected]

[1] N. Bohr, Nature (London) 137, 344 (1936).[2] S. K. Arun, R. Kumar and R. K. Gupta, J. Phys. G: Nucl.

Part. Phys. 36, 085105 (2009).[3] R. K. Gupta, Lecture Notes in Physics 818 Clusters in

Nuclei, ed C. Beck, Vol.I, (Springer Verlag), p223 (2010).[4] S. Chopra, et al., Phys. Rev. C 88, 014615 (2013).[5] R. Yanez, et al., Phys. Rev. C 88, 014606 (2013).

[6] M. K. Sharma, S. Kanwar, G. Sawhney and R. K. Gupta,J. Phys. G: Nucl. Part. Phys. 38, 055104 (2011).

[7] S. Kanwar, et al., Int. J. Mod. Phys. E 18, 1453 (2009).[8] B. B. Singh, et al., Phys. Rev. C 77, 054613 (2008).[9] Niyti, et al., J. Phys. G: Nucl. Part. Phys. 37, 115103

(2010).

12

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FUSION14

Measurement of sub threshold resonance contributions to fusion reactions: The caseof the 13C(α, n)16O astrophysical neutron source

M. La Cognata,1, ∗ C. Spitaleri,1, 2 O. Trippella,1, 3 G.G. Kiss,1, 4 G.V. Rogachev,5

A.M. Mukhamedzhanov,6 M. Avila,5 G.L. Guardo,1, 2 E. Koshchiy,5 A. Kuchera,5

L. Lamia,2 S.M.R. Puglia,1, 2 S. Romano,1, 2 D. Santiago,5 and R. Sparta1, 2

1Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Catania, Italy2Dipartimento di Fisica e Astronomia, Universita di Catania, Catania, Italy

3Dipartimento di Fisica, Universit di Perugia, Perugia, Italy4Institute of Nuclear Research (ATOMKI), Debrecen, Hungary

5Department of Physics, Florida State University, Tallahassee, Florida, USA6Cyclotron Institute, Texas A&M University, College Station, Texas, USA

Fusion reactions play a key role in astrophysics, as theyare responsible of energy production and nucleosynthesisin a number of environments, such as the primordial uni-verse and the stars [1]. The temperatures characterizingthese environments range from 109 K in the case of hotexplosive scenarios down to 106−107 K in the case of qui-escent burning in low-mass stars [1]. Therefore, the rele-vant cross sections have to be known at energies smallerthan ∼ 1 MeV to return reliable model predictions to becompared with today’s high accuracy observations. How-ever, the Coulomb barrier exponentially suppressing thecross section and the electron screening effect, due to theshielding of nuclear charges by atomic electrons, make itvery difficult to provide accurate cross sections. Extrapo-lation is often used to this purpose, sometimes supportedby theoretical calculations. The presence of sub thresh-old resonances might radically alter the expected trendof the extrapolated cross section, leading to untenablesystematic errors on astrophysical models.

The 13C(α, n)16O reaction is an example of reactionscharacterized by strong sub threshold resonances, whichhave to be correctly taken into account to provide re-liable predictions [2]. The 13C(α, n)16O is the neutronsource of the main component of the s-process, respon-sible of the production of most nuclei in the mass range90 < A < 204 [3]. It is active inside the helium-burningshell in asymptotic giant branch stars, at temperatures∼ 108 K, corresponding to an energy interval where the13C(α, n)16O is effective of 140− 230 keV.

In this region, the cross section is dominated by the−3 keV sub-threshold resonance due to the 6.356 MeVlevel in 17O. Therefore, the Coulomb corrected cross sec-

tion, the so-called astrophysical factor S(E) [1], shows asteep increase significantly changing the trend with re-spect to the case of no resonance. Notwithstanding thatit plays a crucial role in astrophysics, no direct measure-ments exist inside the 140− 230 keV range [2]. The con-tribution of the -3 keV resonance is still controversial asextrapolations, e.g., through R-matrix calculations, andindirect techniques, such as the asymptotic normaliza-tion coefficient (ANC), yield inconsistent results. Thediscrepancy amounts to a factor of 3 or more right at as-trophysical energies (see [4, 5] for a detailed discussion).

Therefore, we have applied the Trojan Horse Method(THM) to the 13C(α, n)16O quasi-free reaction to achievean experimental estimate of such contribution. For thefirst time, the ANC for the 6.356 MeV level has been de-duced through the THM as well as the n-partial width,allowing to attain an unprecedented accuracy in the13C(α, n)16O study. Though a larger ANC for the 6.356MeV level is measured, our experimental S(E) factoragrees with the most recent extrapolation in the litera-ture in the 140−230 keV energy interval, the accuracy be-ing greatly enhanced thanks to this innovative approach,merging together two well establish indirect techniques,namely, the THM and the ANC. The results have beenrecently published in Physical Review Letters [4] and inthe The Astrophysical Journal [5].

The approach developed for the investigation of the13C(α, n)16O reaction at low energies might find appli-cation in the study of a number of resonance reactions adeep sub Coulomb energies, where direct measurementsare impossible.∗corresponding author: [email protected]

[1] C. Rolfs & W.S. Rodney, Cauldrons in the Cosmos(Chicago: Univ. Chicago Press) 1988.

[2] M. Heil et al., Phys. Rev. C 78, 025803 (2008).[3] M. Busso, R. Gallino & G.J. Wasserburg, Annu. Rev. As-

tron. Astrophys. 37, 239 (1999).[4] M. La Cognata et al., Phys. Rev. Lett. 109, 232701 (2012)[5] M. La Cognata et al., Astrophys. J., in press (2013)

13

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FUSION14

Transfer reaction studies in inverse kinematics with the magnetic spectrometerPRISMA

L. Corradi11INFN - Laboratori Nazionali di Legnaro - Italy

Via multinucleon transfer reactions at Coulomb bar-rier energies one can investigate nucleon-nucleon corre-lation in nuclei, the transition from the quasi-elastic tothe deep-inelastic regime and channel coupling effects insub-barrier fusion reactions [1].

The advent of the last generation large solid anglemagnetic spectrometers coupled to large gamma arraysallowed to perform gamma-particle coincidences, thusstudying at the same time reaction mechanism and nu-clear structure for nuclei produced via nucleon transferor deep-inelastic reactions, especially in the neutron-richregion [2, 3]. Ongoing studies are of primary importancefor reactions to be done with radioactive ion beams wheremultinucleon transfer has been shown to be a competi-tive tool for the study of neutron-rich nuclei, at least forcertain mass regions.

In the last period, with the PRISMA spectrometer wefocused on two main classes of experiments, both per-formed in inverse kinematics, i.e. transfer measurementsat sub-barrier energies [4, 5] and direct identification ofheavy partner products. These inverse kinematics exper-iments are particularly useful to efficiently detect bothbinary partners and to study the production yield in theneutron rich regions. Besides the “light” partner prod-ucts, the “heavy” partners are presently receiving pe-culiar attention [6, 7]. In fact, certain regions of thenuclear chart, like that below 208Pb or in the actinidesand transactinides, can be hardly accessed by fragmenta-tion or fission reactions, and multinucleon transfer rep-resents a suitable (if not the only one) mechanism toapproach those neutron rich areas. We performed a

first test-experiment with the reaction 197Au+130Te atElab=1070 MeV, using a 197Au beam delivered by thePIAVE+ALPI accelerator complex at Elab=1070 MeV,and detecting with PRISMA at angles close to the graz-ing one both projectile like and target like ions. The firstphysics goal was to get the A, Z and Q-value distribu-tions measuring the “light” reaction products. Since forthese rather heavy ions secondary processes should play anon negligible role, it will be interesting to compare finalyields (cross sections) with those expected from theoret-ical models, already successfully applied for lower masssystems. In particular, via the 2 proton stripping (−2p)and 4 neutron pick-up (+4n) channel one should be ableto get close to 132Sn, a benchmark nucleus. The secondgoal was to compare the yields of the “light” partner withthat of the “heavy” one. With neutron poor projectileson heavy targets only proton stripping and neutron pick-up channels are available, while with neutron rich projec-tiles also proton pick-up and neutron stripping channelsopen up. This corresponds, for the heavy partner, tothe population in the “south-east” direction, leading tothe neutron rich Pt-Os heavy region. As said before, acompetitive process is evaporation (and/or fission) whichshifts the final yield to lower mass values. It is thereforeextremely important to get quantitative information onthe final yield distributions and compare them with the-oretical predictions.

In the following, a discussion on these last experimentswill be presented, with emphasis on the importance forfuture investigations in the heavy mass regions.

[1] L. Corradi, G. Pollarolo and S. Szilner, J. of Phys. G: Nucl.Part. Phys. 36, 113101 (2009).

[2] S. Szilner et al, Phys. Rev. C 76, 024604 (2007).[3] S. Szilner et al, Phys. Rev. C 84, 014325 (2011).[4] L. Corradi et al., Phys. Rev. C 84, 034603 (2011).[5] D. Montanari et al., NN2012, S. Antonio, Texas (USA)

May 27 - June 1, 2012, J.of Phys. G 420, 012161 (2012).[6] L. Corradi et al., Nucl. Instr. and Methods in Physics Re-

search B 317, 743 (2013).[7] Y. X. Watanabe et al., Nucl. Instr. and Methods in Physics

Research B 317, 752 (2013).

14

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FUSION14

Exploring the influence of transfer channels on fusion reactions:the case of 40Ca+58,64Ni

S. Courtin,1, ∗ D. Bourgin,1 F. Haas,1 A.M. Stefanini,2 G. Montagnoli,3 N. Rowley,4 L.Corradi,2 E. Fioretto,2 A. Goasduff,5 D. Montanari,3 F. Scarlassara,3 and S. Szilner6

1Institut Pluridisciplinaire Hubert Curien (IPHC), Strasbourg, France2INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy

3Dipartimento di Fisica, Universita di Padova, and INFN, Sezione di Padova, Italy4Institut de Physique Nucleaire, Orsay, France

5CSNSM, Orsay, France6Ruder Boskovic Institute, Zagreb, Croatia

Fusion-evaporation is the dominant reaction mecha-nism in medium-light heavy-ion collisions at relativelylow bombarding energies. The main features observedat these energies, are the enhancement of the fusioncross-section at the Coulomb barrier (CB) and at mod-erate subbarrier energies, and the hindrance of the cross-section at deep subbarrier energies. Fusion cross-sectionsaround the CB have been discussed extensively to bedriven by couplings of the relative motion of the collid-ing nuclei to their low energy surface vibrations and/orstable deformations. The corresponding coupled-channelcalculations of the distributions of barriers and their ex-traction from precise cross-section measurements have re-vealed to be a powerful tool to better understand the roleof couplings to collective degrees of freedom of the targetand projectile [1].This contribution reports on a recent study of the fu-sion process in the Ca+Ni systems. This work has beentriggered by outstanding results obtained recently in theCa+Ca [2] systems, and also by the pioneering studies ofthe Ni+Ni systems [3]. Previous fusion measurements ofthe symmetric 40Ca+40Ca and 48Ca+48Ca systems andthe asymmetric 40Ca+48Ca one have been performed atthe LNL (Laboratori Nazionali di Legnaro, Italy) Tan-dem Accelerator down to very low subbarrier energies.All Ca+Ca systems have shown large fusion hindranceat deep subbarrier energies [2]. For the asymmetric

40Ca+48Ca system, hindrance effects show up at lowerenergies than in the other two systems and it has beenconcluded that it is necessary to take into account thepositive Q value transfer channels to reproduce the fu-sion cross-section below CB. In a similar way, effects onthe fusion excitation function attributed to transfer chan-nels have been invoked in a study of the fusion excitationfunction of the 58Ni+64Ni system by Beckerman et al.[3].Based on these two observations, we have decided to per-form accurate cross-section measurements in the cross-systems Ca+Ni to identify eventual effects of the neu-tron excess on fusion in the distribution of barriers energyrange. Experimental data have been taken at the LNLTandem for the 40Ca+58,64Ni systems taking advantageof the LNL electrostatic deflector in its upgraded version,making use of large size micro-channel plate and silicondetectors. We have thus been able to extend to muchlower energies previous 40Ca+58Ni [4] data and to mea-sure for the first time a fusion excitation function for the40Ca+64Ni system. The corresponding cross-sections anddistributions of barriers extracted from these accuratedata will be presented. State-of-the-art coupled-channelcalculations will be presented to discuss the subbarrierfusion excitation function behavior in terms of the in-fluence of neutron transfer channels in the 40Ca+64Nisystem.∗Corresponding Author: [email protected];

Permanent address: IPHC, Strasbourg, France

[1] N. Rowley, G. R. Satchler, and P. H. Stelson, Phys. Lett.B 254, 25 (1991)

[2] G. Montagnoli et al. Phys.Rev. C 85, 024607 (2012) andreferences therein.

[3] M. Beckerman et al., Phys.Rev.Lett. 45, 1472 (11980).[4] B. Sikora et al., Phys.Rev. C 20, 2219 (1979).

15

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FUSION14

Superheavy element research with the gas-filled recoil separator TASCA at GSI

X. Derkx1, 2, ∗ and the TASCA collaboration1Helmholtz Institute Mainz, 55099 Mainz, Germany

2Johannes Gutenberg-Universitt Mainz, 55099 Mainz, Germany

The quest for new elements, which is a basic drivingforce for the journey to the island of stability, is a pow-erful engine to stretch the limits of our knowledge in nu-clear physics. So far, the heaviest confirmed element isLivermorium (Z = 116) and the heaviest claimed one isZ = 118.

The TransActinide Separator and ChemitryApparatus (TASCA) is a gas-filled recoil separatorfor the production and the study of the physical andchemical properties of superheavy elements. It isoptimised for hot fusion reactions on actinide targets.

For a couple of years, intensive efforts focused on thesearch of new superheavy elements by using state-of-the-art beams (50Ti), targets (249Bk, T1/2 = 320 days), sep-arator (TASCA), detectors and electronics (digital).

In this contribution, the current physics programme atTASCA will be described, highlighting the recent results,including:

• the measurement of the X-rays emitted by theproducts of the reactions 48Ca + 243Am→ 291115∗with TASISpec ;

• the production of Z = 117 element by 48Ca +249Bkfusion-evaporation reaction and the study of itsalpha-decays ;

• the attempt of producing Z = 119 and Z = 120 witha 50Ti beam on 249Bk and 249Cf targets during highsensitivity long campaigns ;

• the analysis of the so-called background transferproducts from these experiments, which may im-prove our understanding of the reaction mecha-nisms.

∗corresponding author: [email protected]

16

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FUSION14

Complete and incomplete fusion reaction in the interaction of 16O+55Mn system below7 MeV/A: Measurement and analysis of excitation functions

Avinash Agarwal,1 Sunil Dutt,1, ∗ Munish Kumar,1 R. Kumar,2

Kamal Kumar,3 Sabir Ali,3 I. A. Rizvi,3 and A. K. Chaubey4

1Department of Physics, Bareilly College, Bareilly, 243 005,India2Inter University Accelerator Centre, New Delhi,110 067, India

3Department of Physics, Aligarh Muslim University, Aligarh, 202 002,India4Department of Physics, Addis Ababa University, Addis Ababa, Ethiopia

Investigation of different reaction mechanisms involvedin the Heavy Ion (HI) induced reactions e.g., complete fu-sion (CF), incomplete fusion (ICF), direct reactions etc.have been a point of interest even at incident energiesas low as 5 MeV/A. Recent studies report breakup of12C, 16O and 20Ne in to 4He, 8Be and 12C projectilefragments and their incomplete fusion with the target[1–5]. As a part of our ongoing program to study CFand ICF reaction mechanisms, we have made an attemptto measure the excitation functions for the evaporationresidues(ERs)identified in the interaction of 16O + 55Mnsystem, which is an extension to our earlier experimentfor 12C + 59Co, and 20Ne +51V systems[6, 7]. The moti-vation of this experiment is to study the breakup of 16Oin reactions below 7 MeV/A and to compare the excita-tion functions for 12C, 16O and 20Ne induced reactionswith different targets leading to the same composite sys-tem (71As in this case). This is a complementary studyto Ghoshal’s experiment [8] where he confirms the Bohrcompound Nucleus theory by showing that, the samecompound nucleus formed by different projectiles viz.,protons and alpha, decay in the same way. The experi-ment has been performed in General Purpose ScatteringChamber (GPSC) using 15UD Pelletron facility at InterUniversity Accelerator Centre (IUAC) New Delhi, India.

The activation technique was used to measure the excita-tion functions for the various ERs produced in the inter-action of 16O with 55Mn. The targets were made usingvacuum evaporation technique onto 2mg/cm2 aluminumbacking. The activities induced in the target foils werefollowed offline using pre-calibrated HPGe detector. TheERs were identified by their characteristic gamma-raysand decay curve analysis. The excitation functions forvarious ERs have been calculated using the formulationgiven elsewhere [9]. The measured excitation functionswith theoretical predictions show considerable enhance-ment in cross-sections for some isotopes indicating thatthe process other than compound nucleus decay play animportant role in the production of these isotopes. Thelarge difference in our measured and theoretically pre-dicted values as obtained from statistical model codes,gives clear signature that the role of incomplete fusionfor these channels is important in the considered energyrange. The comparative study of the excitation functionsof ERs produced in the interaction of 12C + 59Co, 16O+ 55Mn and 20Ne + 51V systems evidently shows thatin case of HI induced reactions, the effect of angular mo-mentum and coulomb barriers in the entrance channelbecome significant in determining the decay mode of thecomposite system.∗corresponding author: [email protected]

[1] Kamal Kumar, et al., Phys. Rev. C87, 044608 (2013).[2] F. K. Amanuel, et al. Phys. Rev. C84, 024614 (2011).[3] Abhishek Yadav, et al., Phys. Rev. C85, 034614 (2012).[4] Avinash Agarwal, et al. EPJ web of Confrences38, 17001

(2012).[5] A. Agarwal, et al., Int. J. Mod. Phys. E17, 393 (2008).[6] Avinash Agarwal, et al., Proc. of DAE Symp. on Nucl.

Phys. Vol. 46B, 286 (2003).[7] Avinash Agarwal, et al., Proc. of DAE Symp. on Nucl.

Phys. Vol.50, 319 (2003).[8] S. N. Ghoshal, Phys. Rev.80, 939 (1950).[9] Avinash Agarwal, et al., Phys. Rev. C65, 034605 (2002).

17

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FUSION14

1

A unified homographic law for fusion excitation functions above the barrier

P. Eudes,1, ∗ Z. Basrak,2 F. Sebille,1 V. de la Mota,1 and G. Royer11SUBATECH, EMN-IN2P3/CNRS-Universite de Nantes, Nantes, France

2Ruder Boskovic Institute, Zagreb, Croatia

We report on a comprehensive systematics of nearly400 fusion-evaporation and/or fusion-fission cross sectiondata σfus for a very large variety of in total 81 reac-tion systems over a laboratory energy range ∼ 3A – 155AMeV. Scaled by reaction cross section σreac and expressedas a function of center-of-mass energy per nucleon Eavail,so normalized fusion cross section σN = σfus/σreac dis-play a universal behavior which is not within experimen-tal error bars affected by a value of system mass, massasymmetry or system isospin [1]. On that way we

(i) Establish the first exhaustive systematics of com-plete fusion as well as of summed complete and incom-plete fusion cross sections in in the fusion region III.

(ii) Assess the global characteristics of fusion excitationfunction and reveal to which extent one may render itindependent of reaction system.

(iii) Extract the main characteristics of both completefusion and incomplete fusion components of fusion.

Derived from fundamental formulas for reaction crosssection a homographic function in energy

f(x)=a+b

c+ x, (1)

with x = Eavail and a, b, and c the fit parameters, de-scribes correctly the experimental normalized σN . Fit-ting by Eq. (1) was carried out for the all 344 availablecomplete fusion plus incomplete fusion σN data pointsand for 60 complete fusion σN data points resulting fromthose twelve experiments which have explicitly been de-signed to measure both complete fusion and incompletefusion reaction components.

The deduced homographic laws for both complete (seefull dark-red curve in Fig. 1) and summed complete andincomplete fusion excitation functions (see red dashedcurve in Fig. 1) allows drawing the main properties ofthese excitation functions. The limiting energy for thecomplete fusion is at about Eavail ≈ 6.2 MeV/nucleon.The onset of the incomplete fusion excitation functionis at 1.6, it reaches a maximum at 6.2 amounting notmore than 0.1σreac and it extincts at 13.2 MeV/nucleon

of Eavail, respectively. The regularity in fusion data isparticularly obvious for the evaporation-residue subset ofthe data ensemble. Adding the fusion-fission data compo-nent does not alter the general data trend but somewhatobscures it owing to their larger uncertainty.

0

0.2

0.4

0.6

0.8

1

0 5 10 15

AVAILABLE ENERGY (MeV/A)

NO

RM

AL

IZE

D C

RO

SS

SE

CT

ION

28Si+12C16O+27Al32S+12C20Ne+26Mg20Ne+27Al35Cl+12C

16O+40Ca28Si+28Si32S+24Mg19F+40Ca32S+27Al35Cl+24Mg23Na+40Ca28Si+40Ca

0

0.5

1

0.5 1 1.5

INVERSE AVAILABLE ENERGY 1/(MeV/A)

NO

RM

AL

. CR

OS

S S

EC

TIO

N

FIG. 1: (Color online.) Complete fusion σN as a function ofEavail (main panel) and as a function of the inverse of the sameenergy (inset) from those measurements which have reporteddata on both complete and incomplete fusion. The fit withthe homographic function (Eq. (1)) in the fusion region IIIis shown as full dark-red curve in both panels. Short-dasheddark-red curve is due to the same kind of fit of the systemexcitation energy, i.e. Eavail corrected for reaction Q-valueper nucleon. The dark-green dash-dotted curve in inset is dueto the same kind of fit to the fusion region II. The backgroundband around the best fit curve in the main panel is due to theerrors on the fit parameters. Red dashed curve is the best fitcurve obtained by fitting the complete fusion plus incompletefusion σN data points with Eq. (1). Blue dotted curve is thedifference of both.

∗corresponding author: [email protected]

[1] P. Eudes et al., Europhys. Lett. 104, 22001 (2013).

18

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FUSION14

Fusion and 1n stripping reactions in the 9Be+169Tm, 181Ta and 187Re systems

Y. D. Fang,1, ∗ P. R. S. Gomes,2 M. L. Liu,1 X. H. Zhou,1 Y. H. Zhang,1 N.T. Zhang,1 J. G. Wang,1 B. S. Gao,1 Y. H. Qiang,1 S. Guo,1 and Y. Zheng1

1Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, People’s Republic of China2Instituto de Fısica, Universidade Federal Fluminense,

Avenida Litoranea s/n, Gragoata, Niteroi, Rio de Janeiro, 24210-340, Brazil

In FUSION 14 I will talk about some preliminary re-sults of fusion and one-neutron stripping reactions in9Be+169Tm, 181Ta and 187Re systems. The experimentwas performed recently at Institute of Modern Physics.The 9Be beam at energy of 50.4 MeV was provided by thesector focusing cyclotron in the Heavy Ion Research Fa-cility Lanzhou (HIRFL). Three types of 187Re,181Ta and169Tm targets had been used in this experiment. Eachtype of targets contains 15-16 foils with thickness of 200-500 µg/cm2 backed by Al catchers of thickness about 1mg/cm2. The irradiated stack covered the desired en-ergy range of 30-50 MeV, and was irradiated for 12 hfor above barrier and 15 h for sub-barrier. The incidentflux of the 9Be beam was determined from a electron sup-pressed Faraday cup, as well as from the counts of the twoRutherford monitors kept at ±30 degree to the beam di-rection.The activities induced in the target-catcher werefollowed off-line using eight groups of HPGe detectors,each group containing two HPGe detectors (face to face).The cross sections of CF, ICF and 1n stripping have beenextracted in these three systems. The CF suppression aswell as experimental ICF probability FICF have been ob-tained in these three systems (see Fig. 1 as a example).

0.10

1.00

9Be+187Re

FICF

EBeam

32.00 37.00 42.00 47.00 52.00

s ICF/sTF

(MeV)

FIG. 1: ICF probability as a function of beam energies.

∗corresponding author: [email protected]

19

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FUSION14

A new neutron-deficient isotope 205Ac on gas-filled separator SHANS

Z. Y. Zhang,1 Z. G. Gan,1, ∗ L. Ma,1, 2, 3 L. Yu,1, 2 and H. B. Yang1, 2, 3

1Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China2University of Chinese Academy of Sciences, Beijing 100049, China

3School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China

A gas-filled recoil separator, SHANS (Spectrometer forHeavy Atoms and Nuclear Structure) [1], consisting ofone dipole magnet and three quadrupole magnets, is con-structed at the Institute of Modern Physics in Lanzhou.The apparatus is used to study the properties of heavynuclei produced in the heavy-ion-induced fusion evapora-tion reactions. The helium gas is filled in the field regionof the separator at a pressure of about 1 mbar. Themaximum magnetic rigidity of the dipole magnet is 2.9Tm.

Recently, a new neutron-deficient isotope 205Ac wasproduced in the complete-fusion reaction 169Tm(40Ca,4n)205Ac. The evaporation residues (ER) were separat-ed in-flight by the gas-filled separator SHANS and subse-quently identified by the α-α position and time correla-tion method. Projectiles of 40Ca from the SFC cyclotronof HIRFL were accelerated to an energy of 198 MeVand the typical beam intensity was about 100 pnA. The169Tm target with thickness of 400 µg/cm2 was evapo-rated on a carbon foil of 40 µg/cm2 and covered with acarbon foil of 10µg/cm2. The effective beam energies atthe center of target and irradiation times (in parentheses)were 196 MeV (61 h) and 183 MeV (19 h).

Three 300 µm thick position sensitive silicon detectors(PSSD) and eight non-position sensitive side silicon de-tectors (SSD) were included in a silicon semiconductordetector box (Si-box). The PSSD consisted of 48 verticalstrips with a total active area 150 mm wide by 50 mmhigh. The energy resolution with all strips summedwas measured to be 70 keV (FWHM) at the α parti-cle energy of 6-7 MeV. Using the time windows ∆t(ER-α1)< 0.2 s and ∆t(α1-α2)< 2 s, a two-dimensional spec-trum of mother-daughter (α1-α2) correlations measuredin the PSSD at 196 MeV is shown in Fig. 1.

Three α-decay chains were assigned to the decay ofknown actinium isotope 206Ac. Two of them were ob-served at the 196 MeV bombarding energy and anotherwas observed at 183MeV. The measured average α par-ticle energy and half-life of 206Ac are 7.817(30) MeV and

41+56−15 ms, which are consistent with the decay of Jπ = 3+

ground state of 206Ac reported in Ref. [2]. One quadru-ple correlation α-decay event of 205Ac was observed atthe beam energy of 196 MeV. The measured α parti-cle energy and half-life of 205Ac are 7.935(30) MeV and20+97−9 ms, respectively. Due to the strong trend for an

α decay without spin and parity changes, the observeddecay of 205Ac would probably originate from its 9/2−ground state. The production cross sections of the evap-oration residue 205Ac are estimated to be about 70 pbat bombarding energy of 196MeV and < 0.5 nb at 183MeV.

Mother energy / MeVa

Da

ug

hte

re

ne

rgy /

Me

Va

203m 206Fr, Ra

205Ra

203Fr

202Fr 205m

Ra

206Ac

205Ac

D a

D a a

t

t

(ER- 1) < 0.2 s

( 1- 2) < 2 s

6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4

6.4

6.6

6.8

7.0

7.2

7.4

7.6

6.2

7.8

FIG. 1: Two-dimensional plot of the mother and daughter α-decay energies for correlated ER-α1-α2 events observed in thereaction 40Ca+169Tm at 196 MeV. Maximum search times forthe ER-α1 and α1-α2 pairs were 0.2 s and 2 s, respectively.

∗corresponding author: [email protected]; Permanent ad-dress:509 Nanchang Rd., Lanzhou 730000, China

[1] Z. Y. Zhang et al., Nucl. Instr. Meth. B, http://dx.doi.org/10.1016/j.nimb.2013.05.062 (2013).

[2] K. Eskola et al., Phys. Rev. C 57, 417 (1998).

20

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FUSION14

Shell effects in fission fragment mass distribution

A. Chaudhuri,1 T.K. Ghosh,1, ∗ K. Banerjee,1 S. Bhattacharya,1 C. Bhattacharya,1 S.Kundu,1 J. K. Meena,1 G. Mukherjee,1 R. Pandey,1 T. K. Rana,1 P. Roy,1 T.Roy,1

V. Srivastava,1 A. Saha,1 R. SahaMondal,1 J. K. Sahoo,1 and P. Bhattacharya2

1Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata 700 064, India2Saha Institute of Nuclear Physics, 1/AF, Bidhnannagar, Kolkata 700 064, India

According to Liquid Drop Model (LDM), the limits ofstability against fission would be reached for a nucleuswith Z2/A > 50. Using the systematic of (Z,A) forbeta-stable nuclei, this corresponds to Z >104. So,nuclei with atomic number more than 104, can’t survivesince the LDM fission barrier vanishes. It is becauseof shell effects in nuclei, super heavy elements (SHE)exist. Shell effects in nuclei enhance the stability andheavy nuclei can develop a large barrier to decay. It isgenerally believed that shell effects in nuclei are washedat higher excitation energies. It is of interest to indentifythe excitation energy at which shell effect vanishes. Thisinformation is important in the context of production ofSHE.

With this motivation, recently we have carried outan experiment at Variable Energy Cyclotron Centre,Kolkata, to measure the fission fragment mass distribu-tions in reaction 4He+232Th in wide excitation energyrange (21-64 MeV) at close ( 3 to 4 MeV) energy inter-val. Two large area position sensitive gas detectors [1]were kept at folding angle to detect fission fragments.Masses of the fission fragments were determined fromthe measured time of flight difference and positions (θand φ)of the fission fragments.

Fig1 shows the measured fragment mass distributionsat four representative excitation energies. It is seen (Fig1d) that fragment mass distribution is symmetric athigher excitation energy, as expected from the liquiddrop model prediction. At lower excitation energy (Fig1a), fragment mass distribution is asymmetric withthe higher mass peak around 132 . Liquid drop modelpredicts that the most probable mass split betweenthe fission fragments would be symmetric while shelleffects would provide an extra stability at A=132,owing to 132Sn which is doubly magic, thus driving thedistribution towards asymmetricity. It is clearly seenthat, as the excitation energy is increased, the shapeof the mass distribution changes from asymmetric tosymmetric around 40 MeV, indicating the washing outof shell effects.

In summary, from the measurement of fission fragment

FIG. 1: Measured fragment mass distributions in the reaction4He+232Th.

mass distribution, we have identified the excitationenergy at which shell effect is washed out for a actinidenucleus.The authors thank cyclotron staff for good quality ofalpha beam.

∗corresponding author: [email protected]

[1] T.K. Ghosh et.al, Nucl. Instr. Meth. A540, 285 (2005).

21

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FUSION14

Classical molecular dynamics simulation of weakly-bound projectile heavy-ionreactions

Mitul. R. Morker1 and Subodh. S. Godre1, ∗1Department of Physics, Veer Narmad South Gujarat University, Surat-395007, India

Heavy-ion collisions involving weakly-bound projec-tiles with heavy targets have been studied using Contin-uum Discretized Couple-Channel (CDCC) method [1],a semi-classical coupled channel approximation [2] anda classical trajectory model [3]. In the present work westudy collisions in a 3-body, 3-Stage Classical MolecularDynamics (3S-CMD) model in which the weakly boundnucleus, say 6Li, is considered as a cluster of 4He and 2Hnucleus. The projectile fragments and the target nucleiare constructed in their ground state using a variationalpotential energy minimization code [4] and an NN po-tential between all the nucleons reproducing the groundstate properties of the nuclei.

FIG. 1: 6Li + 209Bi collision at Ecm=42.7 MeV for differentimpact parameters, b.

The weakly-bound projectile fragments are held to-gether in the projectile nucleus in a configuration cor-responding to the observed breakup energy. In the 3S-CMD model calculation the projectile and the target nu-clei are initially brought along their Rutherford trajecto-ries for given initial conditions. The three-body systemis then dynamically evolved from a large initial separa-tion upto distances close to the Coulomb barrier usingClassical Rigid Body Dynamics (CRBD) model [5]. Thisstage is then followed by CMD [4] evolution of the entiremany-body system near and within the projectile-targetbarrier radius. Thus the Coulomb reorientation effectson the deformed target/projectile and their excitationsat close distances are incorporated in the calculations.

Simulations of 6Li + 209Bi at a given collision energyand different impact parameters are shown in Fig. 1(a-d)in the present model calculations. All the essential fea-tures of breakup reactions such as complete fusion, in-complete fusion, no-capture breakup and scattering aredemonstrated. Detailed study of the dynamics; and com-plete and incomplete fusion cross section calculations for6Li + 209Bi, 7Li + 209Bi etc. will be presented.

This work is supported by a grant from DAE-BRNSunder project no. 2009/37/20/BRNS.∗corresponding author: [email protected]

[1] K. Hagino et al, Phys. Rev. C 61, 037602 (2000).[2] H. D. Marta et al, Phys. Rev. C 78, 034612 (2008).[3] Diaz-Torres et al, Phys. Rev. Lett 98, 152701 (2007).[4] S. S. Godre and Y. R. Waghmare, Phys. Rev. C 36, 1632

(1987).[5] P. R. Desai, S. S. Godre, Eur. Phys. J. A 47, 146 (2011).

22

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FUSION14

Three-stage classical molecular dynamics model for simulation of heavy-ion fusionreactions

Subodh S. Godre1, ∗1Department of Physics, Veer Narmad South Gujarat University, Surat-395007, India

Heavy-ion collisions at near barrier energies are dom-inated by deep-inelastic scattering and fusion involvinglarge scale transfer of energy from relative motion to in-ternal excitations. These reactions are also strongly af-fected by the internal structure of the colliding nuclei.For nuclei with static deformation, Coulomb reorienta-tion of the deformed nucleus results in modification ofthe barrier parameters [1, 2]. When the two collidingnuclei come very close to the fusion barrier, apart fromthe reorientation effect the shape of the two nuclei it-self may change due to large-scale excitations resultingin some modification of the barrier [3]. Therefore, it isnecessary to simulate heavy-ion reactions which not onlytake into account long-range reorientation effect but alsothe internal excitations in the nuclei at very close dis-tances in the same calculation.

Various classical macroscopic and microscopic ap-proaches have been used for study of heavy-ion reac-tion. Classical approaches offer clarity of interpretationsand computational ease. Various levels of approxima-tions have been considered and models such as StaticBarrier Penetration Model (SBPM) [4], Classical Rigid-Body Dynamics Model (CRBD) [1, 2], and ClassicalMolecular Dynamics model (CMD) [5] are developed tolook at the effect of specific degree of freedom. In CRBDmodel the two rigid nuclei can not overlap and the energytransfer from the relative motion to internal excitation isneglected after crossing the barrier. No bound state isformed between the two nuclei. Passing over the gener-ated fusion barrier is assumed to be resulting in fusion.However, it is desirable to take into account of the subse-quent capture of the two nuclei behind the fusion barrier.This in-effect can modify the barrier parameters which inturn can modify the calculated fusion cross sections.

The above mentioned problem, in principle, can beovercome by the CMD calculations in which all the de-gree of freedom are included. Dissipation of energy canlead to trapping behind the barrier and result in boundsystem of the two nuclei. However, the long range re-orientation effect require initiation of the CMD at largedistances (2500 fm) like in CRBD calculation, resultingin large computational time for each trajectory and ac-

cumulation of numerical errors. On the other hand, atlarge separation distances one does not expect excitationsof any intrinsic degrees of freedom; thus it is justifiableto assume nuclei to be rigid-bodies at large separationdistances.

Thus to over come the above motioned difficulties andat the same time take advantage of the CRBD and theCMD model calculations a 3-Stage Classical MolecularDynamics (3S-CMD) model [2] consisting of (1) Ruther-ford trajectory stage, (2) CRBD stage and (3) CMD stageis developed for heavy-ion collision simulation whichcombines both the CRBD and CMD in a common sim-ulation code consecutively. This model explicitly takesinto account the long-rage reorientation effect at largeseparations and internal excitations at close separationsas well, seamlessly in the same simulation code.

The results of the dynamical simulation and fusioncross section calculations of 24Mg + 208Pb system willbe presented.

FIG. 1: Ion-ion potential of 24Mg + 208Pb for CRBD,3S-CMD, and CMD calculations [3].

∗corresponding author:[email protected]

[1] P. R. Desai, S. S. Godre, Eur. Phys. J. A 47, 146 (2011).[2] S. S. Godre, P. R. Desai, Nucl. Phys. A 834, 195c (2010).[3] M. R. Morker, S. S. Godre, Proc. Symp. on Nucl. Phys.

57, 560 (2012), ibid 562 (2012).

[4] S. S. Godre, Nucl. Phys. A 734, E17 (2004).[5] S. S. Godre, Y. R. Waghmare, Phys. Rev. C 36, 1632

(1987).

23

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FUSION14

Effect of shell closure on Neutron Multiplicityof fissioning systems 220,222,224Th nuclei

Savi Goyal,1, ∗ S. Mandal,1 Akhil Jhingan,2 B. R. Behera,3 P. Sugathan,2 Ritika Garg,1 K.S. Golda,2 Mohini Gupta,4 Sunil Kalkal,1 Maninder Kaur,3 Suresh Kumar,1 Subinit Roy,5

Mansi Saxena,1 Hardev singh,6 R. Singh,7 Varinderjit Singh,3 Davinder Siwal,1 and S.Verma1

1Department of Physics and Astrophysics, University of Delhi2Inter University Accelerator Center, New Delhi

3Department of Physics, Punjab University, Chandigarh4Manipal University, Karnatka

5Saha Institute of Nuclear Physics, Calcutta6Kurukshetra University, Kurukshetra

7AINST, Noida, New Delhi

In recent numerous experiments have been performedto explore the dynamics of fusion-fission reaction. Stud-ies show that the measured pre-scission neutron multi-plicities in a heavy ion induced fusion reaction are sub-stantially higher than those predicted by the standardstatistical model of fission[1]. The large excess of neu-trons which are emitted before the nucleus undergoes fis-sion is interpreted as arising from the dynamical effects inthe fission decay process. Investigation also shows shellclosure plays a crucial role in investigating the fusion-fission dynamics. A shell closed nuclei has a high bindingenergy, which lowers the probability of particle emissionand on the same time shell closed nuclei has high fissionbarrier, which enhances the probability of particle emis-sion[2]. Therefore it will be interesting to study the shelleffects of projectile and target on the neutron multiplic-ity from the fissioning systems. In the present paper, weare reporting the study of pre and post scission neutronmultiplicities and the shell effects for 16O + 204,206,208Pbsystems.

The experiment was carried out at Inter UniversityAccelerator Centre (IUAC) using pulsed 16O beam from90 MeV to 120 MeV (E∗

CN = 40 to 64 MeV) from pel-letron and the energy booster LINAC using National Ar-ray of Neutron Detectors. Fission Fragments were de-tected by two position sensitive multiwire proportionalcounters (MWPC) placed inside the chamber at foldingangles. Self supporting isotopically enriched targets of208,206,204Pb were used of thickness 1.5 mg/cm2. Two sil-icon surface barrier detectors were also placed inside thechamber to monitor the movement of beam spot. Twentyfour liquid scintillator detectors were placed outside thescattering chamber for the detection of neutrons. Dis-crimination between neutrons and gammas was made by

using the pulse shape discrimination modules based onzero cross and time of flight technique(TOF).

The pre and post - scission neutron multiplicities wereextracted by fitting the observed neutron energy spectrawith three moving source evaporation components (presicission emission assumed from CN and post scissionfrom two fully accelerated fission fragments) using theWatt expression[3]. The fitting was performed by consid-ering the post-scission multiplicity and the temperaturesto be the same for both the fission fragments. A typicalfitting of the double differential neutron multiplicityspectra at various angles for 16O+208Pb at 100.5 MeV isshown in FIG.1

0 2 4 6 8 10

Energy (MeV)1e-06

1e-05

0.0001

0.001

0.01

0.1

1

Neu

tron

/ (F

issi

on M

eV S

r)

θ = 135 o

0 2 4 6 8 10

Energy (MeV)1e-06

1e-05

0.0001

0.001

0.01

0.1

1

Neu

tron

/ (F

issi

on M

eV S

r)

θ = 300

FIG. 1. Neutron multiplicity spectra (stars) for the16O+208Pb at Elab = 100.5 MeV along with the fits for thepre-scission (dotted curve), post-scission from one fragment(dashed curve) and that from the other (dot-dashed curve).The solid curve represents the total contribution.

Preliminary analysis shows that the shape contributionfor the three neutron emitting sources vary dramaticallywith the correlation angle between the neutron emittingsources and the direction of neutron emission. It alsoshows the effect of deformation of the entrance channelpartner on the neutron multiplicity is not remarkable.

[1] N. Bohr and J. A. Wheeler, Phys. Rev. 56, 426 (1939) [2] Y. E. Wei Chin.phys.lett. , vol 20, No.4 , 482 (2003)[3] D. Hilscher et al. Phys. Rev. C 20, 576 (1979)

∗ email: [email protected]

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FUSION14

Influence of deformation of projectile on the neutron multiplicityfor the 28Si + 204,206,208Pb system

Savi Goyal,1, ∗ S. Mandal,1 Akhil Jhingan,2 B. R. Behera,3 P. Sugathan,2 Appanababu,2

Ritika Garg,1 K. S. Golda,2 Mohini Gupta,4 Subinit Roy,5 Mansi Saxena,1

Dharmendra Kumar,2 Suresh Kumar,1 Hardev singh,6 R. Singh,7 and S.Verma1

1Department of Physics and Astrophysics, University of Delhi2Inter University Accelerator Center, New Delhi

3Department of Physics, Punjab University, Chandigarh4Manipal University, Karnatka

5Saha Institute of Nuclear Physics, Calcutta6Kurukshetra University, Kurukshetra

7AINST, Noida, New Delhi

Since the advent of high energy heavy ion beams, con-siderable progress has been made in our knowledge ofthe fission of highly excited compound nuclei formedin heavy-ion induced fusion reactions, both theoreticallyand experimentally. The experimental probes to under-stand the fusion-fission reaction dynamics are the mea-surement of n, p, α, giant dipole resonance, γ ray, evapo-ration residues and fission fragments. A series of exper-imental data [1] strongly suggest there is excess particleemission than predicted by Bohr and wheeler theory fromthe composite fissioning system. It has been interpretedas a time delay in the fission process which arises due todynamical effects in the fission decay. Pre scission neu-trons are the most commonly used probe to study sucheffects. An advantage of using this probe is the absenceof the coulomb barrier experienced by neutron.

28Si has a partially filled shell and 204,206,208Pb haspartly filled and as well as doubly shell closed nuclei re-spectively. Hence it will be interesting be investigate theeffect on the neutron multiplicity when a partly filledprojectile interact with the shell closed and partly closednuclei.

The 28Si pulsed beam was delivered by superconduct-ing linear accelerator- Pelletron facility of Inter Univer-sity Accelerator Centre. Neutron Multiplicity was mea-sured using National Array of Neutron Detectors in co-incidence with fission fragments. The self-supportingisotopically enriched targets (204,206,208Pb) of thickness∼1.5 mg/cm2 were used. For the detection of fissionfragments, two Multi-Wire Proportional Counters [2] ofactive area 20×10 cm2 were placed at the folding anglesinside the target chamber. Two silicon surface barrierdetectors were also placed at ±16o w.r.t beam directionfor monitoring purposes. Twenty four liquid scintilla-tor detectors were used for the detection of neutrons inand out of the reaction plane. The. discrimination be-

tween neutrons and gammas was made by using pulseshape discrimination (PSD) based on zero cross tech-nique and Time of Flight (fig.1). The measurements wereperformed for the systems 28Si + 204,206,208Pb from 159MeV to 186 MeV (in lab) in steps of 9 MeV.

FIG. 1: Two Dimensional graph showing separation betweenneutron and gamma

The neutron multiplicities was extracted using theWatt expresion [3]. The multiplicities were decomposedinto the contributions of three moving sources, namely acompound nucleus, and two sources of fully acceleratedfission fragments. The variation of shape contributionwas observed for neutron w.r.t neutron emission source.

*The final result will be discussed during the presen-tation∗email: [email protected]

[1] S.Kailas, Physics Reports 284 ,381(1997)[2] Akhil Jhingan et.al. Review of scientific Instruments 80,

123502(2009)

[3] D.Hilscher et al. Phys. Rev. C 20, 576 (1979)

25

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FUSION14

Revisiting the symmetric reactions for synthesis of super heavy nuclei of Z ≥120

R. K. Choudhury1 and Y. K. Gupta1, ∗1Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India

Extensive efforts have been put to synthesize super-heavy elements (SHE) through two different reactionroutes, the ‘hot-fusion’ (highly asymmetric) [1]) and the‘cold-fusion’ (moderately asymmetric [2]). In the presentpaper, we revisit the near symmetric collisions involvingrare-earth nuclei that might prove useful for synthesis ofcold super-heavy nuclei in the region of Z ≥120. Theadvantages that these reactions offer are: (i) VCoul < |Q|value, (ii) Large g.s. deformations that might enhancenear barrier fusion cross section by channel coupling andlowering of fusion barrier, Bfus, (iii) Good n/p ratio ofCN. Table I shows some relevant data for certain reac-tion routes suggested in the present work using rare-earthnuclei fusion channels.

TABLE I: Relevant data for the reaction routes using therare-earth nuclei.

Reaction ZP ZT Q- Value VCoul Sn

(ZCN ACN) (MeV) (MeV) (MeV)154Sm + 150Nd 3720 -377.5 373.9 7.1

(122, 304)154Sm + 154Sm 3844 -394.9 385.5 7.1

(124, 308)160Gd + 154Sm 3968 -412.2 396.2 7.3

(126, 314)

One expects that due to large ZPZT product, fusionwill be largely hindered. However, for deformed nucleithere is no clear cut understanding of the fusion hin-drance. Fusion-By-Diffusion (FBD) model has been suc-cessfully employed in reproducing the measured excita-tion function for the SHE synthesis up to Z=118 [3].In the FBD model, the evaporation residue cross sec-tion σER for production of a given final nucleus in itsground state is factorized as the product of the partialsticking cross-section (σstick), the diffusion probability(PDiffus), and the survival probability (Psurv). In theFBD model, the probability (PDiffus) that the system in-jected at a point (sinj) outside the saddle point achievesfusion is calculated using the diffusion process over aparabolic barrier [3]. If L stands for the total lengthof di-nuclear shape, then sinj = Linj − 2(R1 + R2) and

PDiffus = 12

(1− erf√H/T) [3, 4], where H is barrier

height opposing fusion along the asymmetric fission val-ley, as seen from the injection point (sinj) and T is thetemperature of the fusing system. In order to estimatethe barrier height, H, sinj is a crucial parameter. In theFBD model, sinj is a free parameter which is adjustedto reproduce the measured fusion cross section. In thework by Cap et al. [4], the sinj values are deduced forseveral cold-fusion systems and plotted as a function ofthe excess of kinetic energy above the mean value of theCoulomb barrier, Ec.m. − B0. The overall trend of sinj

is of decreasing nature with increasing Ec.m. − B0. It isseen that except for the GSI data, all other data are scat-tered. For the purpose of present reactions, sinj valuesfor GSI data are considered and a linear least-square fitis obtained as shown in Fig. 1.

FIG. 1: The injection parameter (sinj) as a function of(Ec.m. − B0) taken from Ref. [4]. The solid line is the leastsquare linear fit, sinj = 1.5985−0.23587(Ec.m.−B0) fm/MeV.

The values for the survival probability (Psurv) havebeen estimated in the similar line as in the Refs. [3, 4].The lower limit of ER cross sections (in 1n channel)for the present systems is arrived to be in the range of1.7×10−11 barn to 3.0 ×10−11 at EX =10 MeV. Even ifwe allow for some uncertainties in the calculations, theresults seem to be quite encouraging for the Z ≥ 120 re-gion. Detailed calculations will be presented. However,experimental investigations using rare-earth nuclear col-lisions will reveal further information on the dynamicsinvolved in these reactions.∗Electronic address: [email protected]

[1] Yu. Ts. Oganessian et al., Nature 400 242 (1999).[2] S. Hofmann et al., Nucl. Phys. A 734 93 (2004).

[3] W. J. Swiatecki et al., Phys. Rev. C 71 014602 (2005).[4] T. Cap et al.,Phys. Rev. C 83 054602 (2011) .

26

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FUSION14

To be announced

K. Hagino1

1Tohoku University, Japan

27

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FUSION14

Elastic scattering of halo nucleus 11Li in the vicinity of Coulomb barrier

M. Hemalatha1, ∗ and S. Kailas11UM-DAE Centre for Excellence in Basic Sciences, Mumbai 400098, India

Considerable improvement in our understanding of nu-clear reactions can be achieved by studying elastic scat-tering of halo nuclei at near-Coulomb barrier energies. Ina recent experiment, the elastic scattering cross sectionsfor 9,11Li off a heavy target (208Pb) at center-of-mass(c.m.) energies 23.1 MeV and 28.3 MeV show a strongreduction with respect to the Rutherford cross section ator below the Coulomb barrier [1]. The observed reduc-tion is attributed to the long-range Coulomb couplingsgenerated when halo projectiles are scattered off heavytargets. These can be taken into account by introducinga dynamic polarization potential in the optical potential.In the present work, elastic scattering cross sections for11Li + 208Pb at Ec.m. = 23.1 MeV and 28.3 MeV areinvestigated using Double Folding (DF) model with andwithout Dynamic Polarization Potential (DPP).

In the DF formalism, the matter density distributionsof target and projectile taking into account the halostructure are folded with a nucleon-nucleon effective M3Yinteraction to obtain the microscopic real DF potential.The imaginary part is considered to be similar to thereal part of the DF potential but with a renormalizationconstant. To take into account dynamic effects due tocoupling of channels, effective DPP is incorporated. TheDPP due to Coulomb excitation of a dipole state withexcitation energy depends explicitly on the B(E1) distri-bution [2]. The complex DPP are determined from themeasured dipole strength distribution for 11Li [3]. Theanalysis is carried out with both real and imaginary partsof the DPP included to the corresponding DF potential.Renormalization constants are chosen to give the best fitto the differential cross-section data. The elastic scat-tering angular distributions from DF calculations with(Fit-1) and without DPP included are shown in Fig. 1.Calculations denoted by Fit-2 in the figure are performedconsidering data for angles only up to 60 degrees. It isclear from the figure that there is a distinct reduction inthe elastic scattering cross section calculated with DPPand good agreement with the data [1], except for back-ward angles. The differential cross sections calculatedwith DPP obtained with Fit-2 give lower χ2 values than

Fit-1 at forward angles for both the energies. The calcu-lation clearly indicates that dynamic polarization poten-tial due to B(E1) is crucial in explaining data for halonuclei at near-barrier energies. As the incident energiesare at or below the Coulomb barrier, the reduction in thedifferential cross section is mainly due to dipole Coulombcouplings which are taken into account in the calculation.

FIG. 1: Calculated elastic scattering angular distributions(relative to Rutherford scattering cross section). The linescorrespond to DF calculations with and without DPP in-cluded.

∗corresponding author: [email protected]

[1] M. Cubero et al., Phys. Rev. Lett. 109, 262701 (2012).[2] M.V. Andres and J. Gomez-Camacho, Phys. Rev. Lett.

82, 1387 (1999).

[3] T. Nakamura et al., Phys. Rev. Lett. 96, 252502 (2006).

28

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FUSION14

Mapping quasifission characteristics in heavy element formation reactions

D.J. Hinde,1, ∗ E. Williams,1 R. du Rietz,1, † M. Dasgupta,1 A. Wakhle,1 C. Simenel,1 and D.H. Luong1

1Department of Nuclear Physics, RSPE, Australian National University, ACT 0200, Australia

98 96 9294

O Ne Mg Si S Ar Ca Ti FeCr Ni

Projectile

C

Targ

et

6 8 10 12 14 16 18 20 22 24 26 28

88

86

84

82

80

78

76

74

72

70

68

66

64

62

60

58

56

54

90

106

108

110

Co

mp

ou

nd

Sy

stem

82

84

86

88

90

92

94

96

100

98

102

104

112

114

116

118

120

Pb

Po

Rn

Ra

Th

U

Pu

Cm

Cf

Fm

No

Rf

Sg

Hs

Ds

Cn

Fl

Lv

X

X

Cf Cm Pu U

Os

Pt

Hg

Pb

Po

Rn

Ra

W

Hf

Yb

Er

Dy

Gd

Sm

Nd

Ce

Ba

Xe

Th

MR

c.m

.

45

90

135

0

180

0.2 0.4 0.6 0.8 1.00.01

10

10

10

10

10

3

4

5

2

0.72

0.72

0.67

0.62

0.82

0.77

[deg

.]

FIG. 1: MAD scatter plots for all reactions studied. Allminiature plots have the same axes as the large MAD (topleft). In the main plot, red vertical and blue diagonal dashedlines correspond to the same projectile and target atomicnumber, respectively, while the horizontal black dotted linesindicate the compound nucleus atomic number. The intensityscale represents counts per pixel in the MAD, proportional tod2σ/dθc.m.dMR. The full grey lines correspond to the notedconstant values of the entrance channel effective fissility.

The formation of heavy and superheavy elements pro-

vides access to extreme nuclear systems in which our un-derstanding of the quantum many-body physics govern-ing nuclear matter can be tested. Research into their for-mation mechanism has provided important insights intothe dynamics of the nuclear fusion process. The dynam-ical evolution that the system undergoes after contact ofthe two heavy colliding nuclei often results in quasifission,a rapid separation of the system formed after contact.This process severely reduces heavy and superheavy el-ement formation cross sections. Our ability to plan theproduction of such nuclei is hindered by a significant gapin our understanding, and our ability to reliably predictprobabilities of quasifission.

Through an extensive series of measurements, the Aus-tralian National University’s Heavy Ion Accelerator Fa-cility and CUBE spectrometer have been used to measuremass-angle distributions for 42 reactions forming heavyelements, with projectiles from C to Ni [1].

Mass-angle distributions (MAD)—showing the fissionmass-ratio as a function of centre-of-mass angle—provideinformation on quasifission timescales in the least model-dependent way. The dependence of our measured mass-angle distributions on the atomic numbers of the projec-tile, target and compound nucleus are shown in Fig.1.Beam energies around 6% above the respective capturebarriers were used to minimise the known influence ofnuclear structure effects seen at near and sub-barrier en-ergies.

Different mappings of mass-angle distribution charac-teristics (including estimated time scales) over the reac-tion landscape show a systematic dependence [1] on en-trance channel and compound nucleus fissilities. Thesewill be presented and discussed.

As well as guiding future experiments, the results pro-vide an empirical baseline to determine the effects of nu-clear structure on quasifission at lower beam energies.This approach—the identification of broad trends, fol-lowed by exploration of finer detail—finds an analogywith the liquid drop model of nuclear masses, in whichlocalized shell effects can be quantified when the under-lying smooth trends are well defined.∗corresponding author: [email protected]

†Current address:Malmo University, Faculty of Technology and So-ciety, 205 06 Malmo, Sweden

[1] R. du Reitz et al., Phys. Rev. C 88(2013)054618

29

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FUSION14

Understanding reaction mechanism of pair transfer using two neutron transfer in 18O+ 206Pb system

V. Jha,1, ∗ B. J. Roy,1 V. V. Parkar,1 H. Kumawat,1 U. K. Pal,1

S. K. Pandit,1 K. Mahata,1 A. Shrivastava,1 and A. K. Mohanty1

1Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, INDIA

There is a renewed interest in the study of two-neutrontransfer reactions as a promising tool to probe the pair-ing correlation in nuclei far from the stability [1]. An in-creased correlation due to the coherence of Cooper pairsin nuclei through the pairing interaction may lead to en-hancement of the absolute value of the two-nucleon trans-fer reaction. However, the reaction mechanism in pairtransfer is complicated and needs to be elucidated to ex-tract the relevant information on pairing correlation. Tostudy the reaction mechanism associated with the pairtransfer processes we have performed experimental andtheoretical study of two neutron stripping reactions inthe 18O + 206Pb system. In addition, we have also inves-tigated the possible coupling effects due to two nucleontransfer by studying the measurement of quasi elasticbarrier distribution for this system.

The experiment is carried out using the 18O beam fromthe BARC-TIFR Pelletron facility at Mumbai. The en-riched target of 206Pb isotope of thickness 250 µg/cm2 on12C backing with a thickness of 30 µg/cm2 is used. Thereaction products are detected and identified by meansof telescopes consisting of silicon surface barrier detectorsin the ∆E- E configuration. Due to the positive Q-value( + 1.917 MeV) for the two-neutron stripping in 18O +206Pb system, the ground state can be easily separated.The angular distribution of the two neutron transfer tothe ground state at Elab=82 MeV is shown in Fig.1. Thedifferential cross sections at several energies, Elab=77-85MeV at angles θlab=170o and 150o are shown in Fig.2.

In order to study the possible enhancement of the twoneutron transfer cross section and test the nuclear struc-ture input, the calculations are performed with mini-mum use of unknown parameters. The optical potentialsare generated from a bare potential that uses a Akyuz-Winther potential for the real part and an internal poten-tial for the imaginary part. The coupled reaction channel(CRC) calculations are performed by including the cou-pling of inelastic excitations of the colliding nuclei. Inaddition, the one neutron stripping reactions from 1d 5

2

and 2s 12

single particle states of 18O to the several sin-gle particle states in 207Pb are included in the calcula-tions. Next, the two-particle transfer reaction, which in-cludes the simultaneous and successive transfer and alsothe contribution of the non-orthogonality effects is in-cluded in the CRC scheme. Microscopic form factors forthe simultaneous transfer using the shell model nuclear

structure inputs are used in the calculations [2]. The re-sult of the calculations are shown by solid lines in Fig.1and Fig.2. Details of the calculation and the experimen-

FIG. 1: The angular distribution of the two neutron transferto the ground state at Elab=82 MeV. The result of CRC cal-culations using both the simultaneous and sequential transferis shown by solid line.

FIG. 2: The measured differential cross sections at severalenergies, Elab=77-85 MeV at angles θlab=170o and 150o.Thesolid lines show the result of CRC calculations using boththe simultaneous and sequential transfer.

tal measurement will be presented during the conference.

[1] Potel G, Barranco F, Vigezzi E and Broglia R A, Phys.Rev. Lett. 105 172502 (2010).

[2] Bayman B F and Chen J Phys. Rev. C 26 1509 (1982).∗corresponding author: [email protected]

30

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FUSION14

Fusion of 32S+90,96Zr, 16O+76Ge and 18O+74Ge: The possible effect of positive Qxn-valueneutron transfer on sub-barrier fusion

H.M. Jia,1, ∗ C.J. Lin,1 H.Q. Zhang,1 F. Yang,1 X.X. Xu,1 Z.H. Liu,1 L. Yang,1 P.F. Bao,1 L.J. Sun,1 and N.R. Ma1

1China Institute of Atomic Energy, P.O. Box 275 (10), Beijing 102413, China

Positive Qxn-value neutron transfer effect on the fu-sion reaction near the Coulomb barrier has become aninteresting topic, especially with the advent of the moreintense radioactive ion beams in the near future. Butthe role is still far from good understanding, even for thestable systems, due to the difficult theoretical descriptionand inconsistent experimental results.

We have measured the fusion excitation functions of32S+90,96Zr, 16O+76Ge and 18O+74Ge at near-barrierenergy range, by using an electrostatic deflector setup atHI-13 tandem accelerator of CIAE. In which some withpositive Qxn-value neutron transfer channels and other-s with negative ones but with similar collective prop-erties for reference. The reaction products were sepa-rated by electrostatic fields, and then identified by theTOF-E method. For these measured systems, large fu-sion enhancement emerges for 32S+96Zr compared with32S+90Zr [1], analysis including the neutron transferchannels based on Zagrebaev’s semiclassical model [2]shows some possible neutron-transfer induced fusion en-hancement at lower energies. But no fusion enhance-ment exists for 18O+74Ge compared with 16O+76Ge al-though of the positive Q2n transfer channel for the firstsystem [3], as shown in Fig. 1. The fusion barrier dis-tributions extracted from the fusion excitation functions

also support the conclusion.Detailed systematic and theoretical analysis of the

multi-neutron transfer mechanism, and the relationshipof the neutron transfer with the fusion enhancement arecrucial for understanding the role. For researching thispoint further experimentally, some stable systems to bemeasured which may have obvious positive Qxn-value ef-fect is proposed.

70 75 80 85 90 95

10-1

100

101

102

103

30 35 40 45 50

32S+90Zr 32S+96Zr

Fus

16O+76Ge 18O+74Ge

Ec.m.

FIG. 1. Experimental fusion excitation functions of32S+90,96Zr, 16O+76Ge and 18O+74Ge at near-barrier energyregion.

[1] H.Q. Zhang et al., Phys. Rev. C 82, 054609 (2010). [2] V.I. Zagrebaev, Phys. Rev. C 67, 061601(R) (2003).[3] H.M. Jia et al., Phys. Rev. 86, 044621 (2012).

∗ corresponding author: [email protected]

31

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FUSION14

Study of complete fusion in 16O+24,26Mg reaction

Shefali Kanwar1, ∗ and Prachi Gupta1, †1Department of Physics, AIAS, Amity University, Noida, India

The study of complete fusion of Compound Nucleus(CN) 40Ca∗ under 16O +24,26 Mg reaction[1] at differ-ent Ec.m values using Dynamical Cluster Decay Model(DCM) has been performed . In this 40Ca∗ is studiedwith spherical symmetry, which is negative Q-value sys-tem. It shows its stability under the natural decay. Here,for 40Ca∗ different cross sections are fitted across differ-ent Ec.m values. The detail is as follow: for 40Ca∗ differ-

ent cross sections are fitted across different Ec.m valuesfor 16O+24Mg (Ec.m. =28.8 MeV, 31.2 MeV, 36.6 MeV,39.6 MeV, 43.2 MeV, 48.6 MeV) and for 16O +26 Mg((Ec.m. = 50.1, 44.5 MeV) and compared with experi-mental data. The role of angular momentum is quite sig-nificant in the decay of excited compound system 40Ca∗.The comparison of DCM [2, 3] calculations with the ex-perimental data shows good agreement.

∗corresponding author: [email protected][email protected]

[1] S. L. Tabor, et al. , Phys. Rev. C 17, 2136 (1978).[2] Raj K. Gupta et al., IREPHY 2 369 (2008): Clusters in

Nuclei. Lecture Notes in Physics 818, 223 (2010), Ed. C.Beck, Springer-Verlag Berlin Heidelberg.

[3] S. Kanwar , M K Sharma, B B Singh, R K Gupta and WGreiner Int. J. Mod. Phys. E 18 1453 (2009).

32

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FUSION14

A Study of Finite Temperature effect in Pairing Correlations in Nuclei

Afaque Karim1 and Shakeb Ahmad1, ∗1Department of Physics, Aligarh Muslim University, Aligarh-202 002, INDIA

We calculate the nuclear pairing gap parameter (∆)and average residual n-p interaction energy (δ) for nu-clei throughout the periodic system in different models.At first, we used the traditional model [1] in which gapparameter and the residual interaction term are functionof atomic mass only. Then, we applied the BCS pair-ing model [2] to find the gap parameter. In this, weobtained the gap parameter by treating all the nucleonsin the nucleus and which can be easily generalized fordifferent type of interactions. Further, the pure pairingforce [3] (G) is introduced in BCS pairing to find the gapparameter. By the use of BCS approximation appliedto a distribution of dense, equally spaced levels we ob-tained expressions for the average neutron pairing gapand average proton pairing gap. This model explainsthe dependencies of average neutron pairing gap and av-erage proton pairing gap upon relative neutron excessand nuclear shape. The result shows that average neu-tron pairing gap is generally smaller than average protonpairing gap. To get some better results, the concept ofquasi particles are introduced in BCS model and anotherset of results are obtained using this concept. Moreover,

the temperature dependence of gap parameter (∆(T)) isalso obtained. For this, the thermal occupation of quasiparticles which are basically fermions are taken into ac-count.

With the use of these different formalism to find thegap parameter,the occupation number are introduced toaccount for pairing which is very much important for allthe light, medium, heavy and superheavy nuclei. Then,the pairing energy of proton-proton , proton-neutron andneutron-neutron are obtained using different techniques.The temperature dependency of paring energy is alsoobtained. We will be presenting the investigations doneusing different techniques for different nuclei, which areas follows:

(i) The variation and comparision of gap parame-ter .(ii) The thermal dependence of gap parameter.(iii) The variation and comparision of paring energy.

Finally, we will discuss the effect of pairing energy termin binding energy formalism.

∗corresponding author:[email protected]; Permanent ad-dress:AMU, Aligarh, India.

[1] Madland and Nix, Nucl. Phys. A476 1 (1988).[2] P.Moller and Nix, Nucl. Phys. A536 20 (1992).[3] P.ring and P. Schuck , The Nuclear Many-Body Problem,

3rd edition, Springer, New York (2004).

33

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FUSION14

Role of neutron rearrangement channels in sub-barrier fusion

Alexander Karpov1, ∗1Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna, Russia

Study of the fusion reactions at near-barrier energieshas a long history. There was a great progress in un-derstanding of the role of coupling of the relative mo-tion with collective degrees of freedom such as rotationsof statically deformed nuclei and vibrations of nuclearsurfaces. The sub-barrier fusion enhancement due tothe excitation of collective states is well understood andcan be properly described within the quantum channel-coupled [1–3] or equivalently within empirical channel-coupled (ECC) [3, 4] calculations. Extra enhancement ofthe sub-barrier fusion was found for some systems hav-ing positive Q-values of the neutron transfer (the 40Ca +90,96Zr case [5], for example) and attributed to the addi-tional coupling with the neutron rearrangement channels.The strong effect of the neutron rearrangement was pre-dicted [6] and then confirmed experimentally [7] for thefusion of weakly bound nuclei such as 6He as comparedwith fusion of 4He.

The neutron rearrangement was quite consistently in-corporated into the ECC approach using semiclassicalapproximation for the transfer probability [6] (note, thatit is rather difficult to include the neutron rearrangementchannels to the quantum channel-coupled approach).

The ECC model with neutron rearrangement has alreadybeen successfully used to reproduce and predict cross sec-tions for the sub-barrier fusion reactions of stable nuclei[6, 10, 11].

However the understanding of the influence of theneutron rearrangement on the sub-barrier fusion is notyet completely clear. For example, recent experimentalstudies reveal that in such systems as 60Ni+100Mo [8],58Ni+130Te [9] no sub-barrier fusion enhancement is ob-served even in the presence of positive and rather largeQ-values for neutron rearrangement. These results showthat there are another factors (beyond large positive Q-values) influencing the enhancement of the sub-barrierfusion due to neutron rearrangement.

This work is aimed at the clarification of the mech-anism of the neutron rearrangement in the fusion reac-tions. Both “positive” and “negative” (with and withouteffect of neutron rearrangement) experimental observa-tions are explained. Sufficient conditions determining therole of neutron rearrangement channels in the sub-barrierfusion are formulated. Finally, we propose several com-binations of colliding nuclei with large effect of neutronrearrangement to be studied experimentally.

∗corresponding author: [email protected]

[1] K. Hagino, N. Rowley, and A.T. Kruppa, Comput. Phys.Comm., 123, 143 (1999).

[2] V.I. Zagrebaev and V.V. Samarin, Phys. At. Nucl., 67,1462 (2004).

[3] V.I. Zagrebaev, A.V. Karpov, A.S. Denikin, V.V.Samarin, and V.A. Rachkov, The fusion code of NRV,http://nrv.jinr.ru.

[4] V.I. Zagrebaev, Phys. Rev. C, 64, 034606 (2001).[5] H. Timmers, et al., Nucl. Phys. A, 633, 421 (1998).

[6] V.I. Zagrebaev, Phys. Rev. C, 67, 061601 (2003).[7] Yu.E. Penionzhkevich, V.I. Zagrebaev, S.M. Lukyanov,

R. Kalpakchieva, Phys. Rev. Lett., 96, 162701 (2006).[8] A.M. Stefanini, et al., Eur. Phys. J. A, 49, 1 (2013).[9] Z. Kohley, et al., Phys. Rev. Lett., 107, 202701 (2011).

[10] H.Q. Zhang, et al., Phys. Rev. C, 82, 054609 (2010).[11] A. Adel, et al., Nucl. Phys. A, 876, 119 (2012).

34

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FUSION14

Study of nuclear structure effect on fusion throughbarrier distribution for the system 28Si+154Sm

Gurpreet Kaur,1, ∗ B. R. Behera,1 A. Jhingan,2 P. Sugathan,2 and N. Rowley3

1Panjab University, Chandigarh-160014, India.2Inter University Accelerator Centre, New Delhi-110067, India.

3Institut de Physique Nucleaire, Orsay Cedex, France.

The effect of the static deformation of permanentlydeformed target, 154Sm and the dynamic deformation ofprojectile, 28Si, on fusion cross section for the system28Si+154Sm near the barrier, has been reported in S. Gilet al. [1], through the fusion excitation function calcula-tions. In the present work, the coupled channel calcula-tions has been performed for the same system to studythese effects through the barrier distribution calculation.The advantage of doing this is that it is much easier tosee the effects of different couplings in the barrier distri-bution than in an excitation function as same informa-tion is obtained in both. It is observed that the struc-ture of the barrier distribution for 16O+154Sm, shown inref. [2], is different when 28Si is taken as projectile. For16O+154Sm, the coupling to rotational states of 154Smand taking 16O as inert explains the data very well. For28Si+154Sm, same type of calculations are performed tak-ing 28Si as inert, but it could not reproduce all featuresof the experimental data. This difference between thecalculated and the experimental excitation function andbarrier distribution indicates that couplings to excitedstates in 28Si cannot be ignored. With coupling to threestates of 154Sm rotational band and a double quadrupoleand single octupole phonon excitation in 28Si, a goodfit is obtained as shown in fig. 1. This confirmed thevibration motion of 28Si and rotational state of 154Smduring interaction between them. The effect of deforma-

80 100 120

Ec.m

(MeV)

1

10

100

1000

σ fus

[(2,1);3][(0,0);6][(0,0);0]

80 100 120E

c.m (MeV)

0

200

400

600

D(E

)=d2 (E

σ fus)/

dE2

FIG. 1: Fusion cross section (left) and barrier distributions(right) for 28Si+154Sm. Dots are the experimental data, dot-ted line for without coupling, dashed and solid lines for cou-pling mentioned inside the figure. The notation [(n1,n2);n3]give the vibrational states, (n1,n2), of 28Si and rotationalstates, n3, of 154Sm.

tion of 154Sm on the interaction potential curve is shownin fig. 2. It is clear from the figure that the barrierget reduced due to the deformation of 154Sm. Here, itis shown for the projectile on the symmetry axis of thedeformed target which is the lowest energy configuration.Also the excitation of 28Si modifies the distribution. So,

8 10 12 14 16 18 20

-0.200.20.40.60.8180

85

90

95

100

105

110

115

Po

ten

tial

Target deformationr (fm)

FIG. 2: Variation of potential between the nuclei as a functionof radial distance (inter-nuclear distance) and deformation oftarget, 154Sm.

the coupling to these degrees of freedom broadens thedistribution of barrier as compared to that for the singlebarrier and thus give rise to lower fusion barriers whichenchanced the fusion cross section below the barrier. Itis also observed that the coupling involving six rotationalstates of 154Sm and three quadrupole phonon excitationof 28Si is also giving a good fit to experimental data withwell shaped peaks. After adding three rotational statesof 154Sm, higher states show very little effect i.e. con-vergence is almost obtained. So, in the full calculationthe number of 154Sm rotational states is reduced to per-mit the inclusion of additional vibrational states of 28Sias latter is showing more effect than the former. Butit is difficult to resolve the structures of the barrier dis-tribution for best fit because the energy step used forexperimental fusion data points is not sufficient. So, weintended to experimentally look at this system using thequasi-elastic method.∗corresponding author: [email protected]

[1] S. Gil et al., Phys. Rev. Lett. 65, 25(1990). [2] M. Dasgupta et al.,Ann.Rev.Nucl.Part.Sci.48,401(1998).

35

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FUSION14

Spin distribution as a probe to investigate the dynamical effects in fusion reactions

Maninder Kaur,1, ∗ B.R. Behera,1 Gulzar Singh,1 Varinderjit Singh,1, † Meenu Thakur,1 Kushal Kapoor,1

Priya Sharma,1 N. Madhavan,2 S. Muralithar,2 S. Nath,2 J. Gehlot,2 G. Mohanto,2 Ish Mukul,2 AkhilJhingan,2 T. Varughese,2 Indu Bala,2 M.B. Chatterjee,2 Davinder Siwal,3 B.K. Nayak,4 and A. Saxena4

1Department of Physics, Panjab University, Chandigarh 160014, India.2Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.

3Department of Physics and Astrophysics, University of Delhi 110007, India.4Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.

Evaporation residue (ER) γ-multiplicity distributionshave been measured for 16O+64Zn (asymmetric) and32S+48Ti (near symmetric) systems in the excitation en-ergy range of 52.8-70.8 MeV, leading to the same com-pound nucleus (CN) 80Sr. The evaporation residue spindistributions have been measured by using 14 elementBGO multiplicity filter [1]. The ERs were separated fromthe beam like contamination with the help of HIRA [2]spectrometer. The γ-rays detected using the BGO multi-plicity filter gave the experimental γ-fold. ER-TOF gatewas used to separate the ER γ-fold from the other con-tamination. The ER-gated γ-fold distribution was con-verted to corresponding γ-multiplicity distribution usingVan Der Werf prescription [3]. The multiplicity distribu-tion was assumed to be a modified Fermi function of theform given as

P (Mγ) =2Mγ + 1

1 + exp(Mγ−Mγo

∆Mγ)

(1)

The two free parameters Mγ0 and ∆Mγ were varied tofit the experimental fold distribution by using the chi-square minimization technique and were used to obtainthe multiplicity distribution. The comparison of exper-imental and fitted fold distributions and extracted mul-tiplicity distributions for both the systems at E* = 57MeV is shown in Fig. 1. From the multiplicity distri-bution, moments of the distribution were also calculatedat all the energies. The comparison of experimental re-sults of both the systems show that mean γ-multiplicityof 32S+48Ti system are lower than those of 16O+64Znsystem.

From this analysis, it is conjectured that the reason forthe reduction in spin distribution for the near symmetricsystem is perhaps due to the fact that the higher partialwaves are not contributing to the fusion process. These

observations are in agreement with the earlier work ofKaur et al. [4] where the observed deviations in the αparticle evaporation spectra, from the statistical modelpredictions, for 32S+48Ti were explained in terms of thesuppression of fusion of higher l values. Present results

0 2 4 6 8 10 12 14-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 10 20 30 40 50

0.00

0.02

0.04

0.06

0.08

0.10

0.12

(a)

Pr

obab

ility

Fold

(b)

16O+64Zn at 71.8 MeV 32S+48Ti at 102 MeV

16O+64Zn at 71.8 MeV 32S+48Ti at 102 MeV

Prob

abili

ty

MultipicityFIG. 1: Comparison of experimental (circles) and fitted (solidlines) fold distributions and (b) extracted γ-multiplicity dis-tribution for both the systems at E* =57 MeV.

show that the entrance channel mass asymmetry has animportant influence on the dynamics of the fusing system.∗Corresponding author: [email protected]

†Present address: GSI Helmholtzzentrum fur Schwerionen-forschung GmbH, 64291 Darmstadt, Germany.

[1] S. Muralithar, DAE Symp. on Nucl. Phys. 34 B, 417(1991).

[2] A.K. Sinha et al., Nucl. Instr. Meth. A 339, 543 (1994).

[3] S.Y. Van Der Werf, Nucl. Instr. Meth. 153, 221 (1978).[4] J. Kaur et al., Phy. Rev. C 70, 017601 (2004).

36

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FUSION14

Study of angular momentum hindrance in heavy ion fusion reactions

Ajay Kumar11Department of Physics, Banaras Hindu University, Varanasi-221005, India

The systematic study of the properties of hot nucleiby detecting the emitted charged particles and neutronsin coincidence with residual nuclei provides very criti-cal information about its nuclear level density. Theseemitted particles also capable to explain the behavior ofthe nucleus at various stages of the deexcitation cascadeprocess. Some papers have claimed [1-4] that experimen-tal evaporation spectra from heavy-ion fusion reactionsat higher excitation energies and angular momenta areno longer consistent with the predictions of the standardstatistical model.

To do a more detailed study, same compound nucleusis needed to populate at same excitation energy throughtwo different entrance channels. So, we have studied, a

set of four compound nuclei, which were populated bymass-symmetric and mass-asymmetric channels, leadingto the same compound nuclei, namely 80Sr∗, 79Se∗, 76Kr∗and 58Ni∗ at same excitation energies, respectively. Thedelayed evolution of the compound system in case of allthe symmetric systems may lead to the formation of atemperature equilibrated dinuclear complex, which maybe responsible for the neutron emission at higher tem-perature, while the protons and alpha particles are evap-orated at a lower temperature and also observed thathigher `-values do not contribute in the formation of thecompound nucleus for all the symmetric entrance channelsystems.

[1] J. Kasagi, B. Remington, A. Galonsky, F. Hass, J.J.Kolata, L. Satkowiak, M. Xapsos, R. Racca, and F.W.Prosser, Phys. Rev. C 31, 858 (1985).

[2] J.J. Kolata, R.M. Freeman, F. Hass, B. Heusch, and A.Gallman, Phys. Lett. 65B, 333 (1976).

[3] J.L. Wile et al., Phys. Rev. C 47, 2135 (1993).[4] A. Saxena, A. Chatterjee, R.K. Choudhry, S.S. Kapoor,

and D.M. Nadkarni, Phys. Rev. C 49, 932 (1994).

37

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FUSION14

Investigation of projectile break-up process in 12C+175Lu system and mass-asymmetryeffect on incomplete fusion

Harish Kumar,1, ∗ D. Singh,2 Rahbar Ali,3 M. Afzal Ansari,1 N. P. M. Sathik,4 Kamal Kumar,1 R.Dubey,5 Indu Bala,5 R. P. Singh,5 S. Muralithar,5 P. Sugathan,5 Rakesh Kumar,5 and N. Madhavan5

1Department of Physics, Aligarh Muslim University, Aligarh - 202 002, India2Centre for Applied Physics, Central University of Jharkhand, Ranchi - 835 205, India

3Department of Physics, G. F. (P. G.) College, Shahjahanpur - 242 001, India4Department of Physics, Jamal Mohammed College, Tiruchirappalli - 620 020, India

5Inter-University Accelerator Centre, New Delhi - 110 067, India

Incomplete fusion (ICF) or massive transfer reactionshave been studied extensively at low projectile energiesbelow 10 MeV/nucleon in recent years. It is now wellestablished that incomplete fusion (ICF) process startcompeting with the complete fusion (CF) process at pro-jectile energies just above the Coulomb barrier [1-3]. TheICF features first observed by Britt and Quinton [4] atlower projectile energies with the break-up of projectileslike 12C, 14N and 16O into α-clusters. Later on Inamuraet al., [5] provided the additional but concrete informa-tion to understand the ICF reaction dynamics. In case ofheavier target nuclei, the evaporation of α-particle fromthe composite system has relatively lesser probability dueto the high Coulomb barrier, thereby, ICF process is ob-served to be the dominating reaction mode as that ofCF process. Literature shows the role of entrance chan-nel mass-asymmetry effect and projectile energy on ICFfraction and strengthens the understanding of ICF re-action dynamics [2-3, 6]. In present work, experimenthas been performed to measure the excitation functions

(EFs) for 12C + 175Lu system at projectile energies ≈4-7 MeV/nucleon with the aim to investigate the depen-dence of ICF fraction on projectile energy, target de-formation and mass-asymmetry of the projectile-targetcombination to get a better understanding of ICF reac-tion dynamics. The recoil catcher activation techniquefollowed by off-line γ-ray spectroscopy has been used.Some residues produced via xn, pxn and αxn/2αxn chan-nels have been identified on the basis of their character-istic γ-rays and half-lives in the interaction of 12C with175Lu target. The experimentally measured EFs of var-ious evaporation residues produced via CF and/or ICFwill be compared with theoretical predictions based onstatistical model code PACE-2 [7]. The enhancement inthe measured EFs with prediction of PACE-2 may beattributed to the ICF contributions. These residues areexpected to be produced via ICF reaction process, in thebreak-up of 12C projectile into 4He and 8Be. Data anal-ysis is going on and final results will be presented.

∗corresponding author: [email protected]; Permanentaddress:Department of Physics, A.M.U., Aligarh - 202002, India

[1] S. Chakrabarty et al., Nucl. Phys. A 678, 355-366 (2000).[2] D. Singh et al., Phys. Rev. C 83, 054604 (2011);

Nucl. Phys. A 879, 107-131 (2012).[3] Rahbar Ali et al., J. Phys. G: Nucl. Part. Phys. 37, 115101

(2010).

[4] H.C. Britt and A.R. Quinton, Phys. Rev. 124, 877 (1961).[5] T. Inamura et al., Phys. Lett. B 68, 51 (1977).[6] H. Morgenstern et al., Phys. Rev. Lett. 52, 1104 (1984).[7] A. Gavron, Phys. Rev. C 21, 230 (1980).

38

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FUSION14

A Study of fusion of 8B+58Ni System in Near Barrier Energy Region

Anju Kumari1, ∗ and Rajesh Kharab1

1Department of Physics, Kurukshetra University Kurukshetra, Hr-136119

The fusion reaction involving weakly bound nuclei,both stable and radioactive, has received a great atten-tion during last two decades [1]. Because of the extraor-dinary large size and very small binding energy of lastnucleon(s) of halo nuclei, the fusion involving these nucleidiffers fundamentally from those involving tightly boundnuclei. Further, due to the presence of Coulomb interac-tion between the valance proton and the remaining core,the proton halo structure is more complex than the neu-tron halo and hence it is quite tempting to investigatethe static and dynamic effects on the fusion of protonhalo nuclei. Very recently Aguilera et al. [2] have mea-sured the fusion cross section of 8B, ground state protonhalo nucleus, on 58Ni target at energies above and be-low the Coulomb barrier and analyzed the data usingWong formula with barrier height, radius and curvatureas free parameters. Subsequently J.Rangel et al [3] ana-lyzed these data through reliable calculation without anyfree parameters and found that experimental fusion crosssection for 8B+58Ni system could not be explained cor-rectly.

16 24 321

10

100

1000

EC.M.

(MeV)

Experimental data

(mb)

Present work (Theory)

FIG. 1: comparison of fusion excitation function of 8B+58Nisystem with experimental data taken from Ref.[2].

Thus in the present work we have made an at-tempt to analyze the fusion excitation function data ofRef. [2] within the framework of quantum diffusion ap-proach. This approach models the channel coupling ef-fects through fluctuation and dissipation [4]. Besides theparameters related to nucleus-nucleus potential, frictionco-efficient and internal excitation width, the averagevalue of relative distance R0 at t=0 is an important in-gredient needed for the calculation. We have here usedan energy dependent expression for R0 and have calcu-lated the fusion excitation function of 8B+ 58Ni systemin near barrier energy region. The calculated results over-estimate the fusion cross section in the deep sub barrierenergy region [Fig 1]. This finding is in accordance withthose of Ref.[3]. It indicates that some dedicated effortslike inclusion of more realistic nucleus-nucleus potential,more realistic friction and other parameters and variationin various parameters arising because of halo structureare still needed to understand this discrepancy betweenthe data and the predictions.

∗corresponding author: [email protected]; Permanent ad-dress:Department of Physics, Kurukshetra University Kurukshetra,

Hr-136119

[1] L. F. Canto et al. , Phys.Rep. 424, 1(2006).[2] E. F. Aguilera et al. , Phys. Rev. Lett. 107, 092701 (2011).[3] J. Rangel et al. , Eur. Phys. J. A 49, 57 (2013).

[4] V. V. Sargsyan et al. , Eur. Phys. J. A 15, 125(2010).

39

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FUSION14

A new technique to determine fusion barrier heights using proximity potentials

Raj Kumari1, ∗ and Aditi Toshniwal21Department of Physics, Panjab University, Chandigarh - 160014, India

2S. V. National Institute of Technology, Surat - 395007, India

Our understanding of the fusion process between theheavy ions at near barrier energies has been enriched dueto the efforts devoted by nuclear community in the fieldof theory and experiments. To reach the island of stabil-ity by creating super-heavy elements, the knowledge offusion barrier is most crucial. We propose a new tech-nique to calculate fusion barrier heights of any fixed tar-get reaction series. In present study, we compute barrierheights for X + 119Sn/197Au reaction series using dif-ferent proximity based potentials. Here, X beam variesfrom Hydrogen to Cobalt. From fig. 1, we can see thatbarrier heights increase monotonically with the mass ofthe projectile for fixed target reactions. The percentagedifference ∆VB% is calculated by using the relation

∆VB%(X + Sn/Au) =VB(X + Sn/Au)

VB(X + Ni)× Z(Sn/Au)× 100

(1)

0

50

100

150

200

250

X + Sn

PROX 77

0

50

100

150

200

250

X + Au

PROX 88

0

50

100

150

200PROX 2000

0

50

100

150

200PROX 2000 DP

0 20 400

50

100

150

200 PROX 2010

0 20 40 600

50

100

150

200PROX MP88

A1

VB (M

eV)

FIG. 1: The barrier heights (VB) are displayed as a functionof mass of the projectile (A1). The circles and squares rep-resent reactions of beam X with Target Sn and Target Aurespectively. Here, X beam varies from 1H to 59Co.

This study is carried out using proximity potentialsProx. 77, Prox. 88, Prox. 2000, Prox. 2000DP, Prox.2010 and Mod-Prox. 88 [1, 2].

2.5

3.0

3.5

4.0

2.5

3.0

3.5

4.0

2.5

3.0

3.5

2.5

3.0

3.5

0 20 402.5

3.0

3.5

0 20 40 602.5

3.0

3.5

X + Au X + Sn

PROX 77

PROX 88

VB%

PROX 00

PROX 00 DP

A1

PROX 2010

VB% (X+Sn)= (V

B(X+Sn) / V

B(X + Ni)) 1/50) 100

PROX MP88

VB%(X+Au) = (V

B(X+Au) / V

B(X+Ni)) (1/79) 100

FIG. 2: The percentage barrier heights (∆VB%) are displayedas a function of mass of the projectile. Symbols have samemeaning as in fig. 1.

We find that ∆VB% for X + Sn and X + Au reactionseries using all these proximity potentials comes out tobe constant i.e. independent of the mass of the projectile(see fig. 2). This is due to the reason that since Coulombpotential is playing a major role so upon scaling w.r.t tothe charge of the fixed target, the effect of Coulomb isreduced. The constant percentage difference representsthat the mass of the projectile is not playing significantrole in the fusion process. Using this technique, we cancalculate the barrier height for the reaction of any beamX with Sn or Au using barrier height of X + Ni reaction.

Depending upon the accuracy of this technique, thisnew formula can be used to find barrier heights of anyfixed target/fixed beam reaction series for which empiri-cal value is not available and hence can be useful in thesynthesis of super-heavy elements.∗[email protected]; Permanent address: Department of

Physics, Panjab University, Chandigarh - 160014, India

[1] I. Dutt and R. K. Puri, Phys. Rev. C 81, 064609 (2010); I.Dutt and R. Bansal, Chin. Phys. Lett. 27, 112402 (2010).

[2] R. Kumar and M. K. Sharma, Phys. Rev. C 85, 054612(2012).

40

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FUSION14

Low energy incomplete fusion: Observation of a significant incomplete fusion fractionat `<`crit

Kamal Kumar,1, ∗ Sabir Ali,1 Tauseef Ahmad,1 I. A. Rizvi,1 Avinash Agarwal,2 R. Kumar,3 and A. K. Chaubey4

1Department of Physics, A.M.U., Aligarh-202002, India2Department of Physics, Bareilly college, Bareilly-243005, India

3Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067, India4Department of Physics, Addis Ababa University, P.O.Box 1176, Addis Ababa, Ethiopia

At moderate excitation energies the dominating fusionprocesses are (i) Complete Fusion (CF) and IncompleteFusion (ICF) [1, 2]. However, in recent years at low pro-jectile energies i.e., near and above the Coulomb barrier(CB), the ICF sets in, where the CF is supposed to playa key role to the total fusion cross-section. The Sum-rulemodel [3] utilizes a sharp cut off approximation. Theprobability of CF is assumed to be unity for `≤ l andexpected to be zero for `> l. This assumption is foundto be consistent only at relatively higher incident ener-gies. Recently, A. Yadav et al. [4] suggested a diffusedboundary in ` distribution for low energy incomplete fu-sion. Hence, low energy incomplete fusion in 16O+165Ho

interaction has been studied. The incomplete fusion frac-tion has been estimated in the framework of statistacalmodel code PACE4 [5]. For a better perception about thediffuseness in ` distribution at low incident energies, thecritical angular momentum `crit for 16O+165Ho system,at which the pocket in the entrance-channel potentialdisappears, has been calculated using the prescription ofWilzyanski et al. [3]. The fusion ` distributions for thecompound nucleus in the above mentioned interaction atstudied energies have been calculated using the code CC-FULL [6]. A significant incomplete fusion fraction wasobserved at `<`crit.

∗corresponding author: [email protected]

[1] Kamal Kumar, et al., Phys. Rev. C 87, 044608 (2013).[2] F. K. Amanuel, et al., Phys. Rev. C 84, 024614 (2011).[3] J. Wilczynski et al., Phys. Rev. Lett. 45, 606 (1980).[4] A. Yadav et al., Phys. Rev. C 85, 064617 (2012).

[5] A. Gavron, Phys. Rev. C 21, 230 (1980).[6] K. Hagino et al., Comput. Phys. Commun. 123, 143

(1999).

41

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FUSION14

Quantum Molecular Dynamical Model for the incident energy on and above 50MeV/nucleon

Sanjeev Kumar1, ∗1Amity Institute of Nuclear Science and Technology, Amity University, Noida 201303, Uttar Pradesh

The unique theoretical model, which can describe thevarious phenomenas in the wide range of incident en-ergy, is of great interest these days. In the presenttext, we are going to present the findings of QuantumMolecular Dynamical (QMD) model and its extension,which can describe the variety of phenomenas from 50 to1000 MeV/nucleon. The major phenomena in this en-ergy range are multifragmentation, collective flow, bal-ance energy, elliptical flow, transition energy, liquid gasphase transition and particles production (pion, kaon, Σ)etc.. The detailed analysis of the above phenomena withQMD model is presented in the following ref.[1–7]. Thesoft equation of state for the symmetric nuclear matteris concluded from these results in the energy range de-scribed above.With the passage of time and keen interest of nuclear

community towards the asymmetric nuclear matter equa-tion of state, the QMD model is extended for Isospineffects, dubbed as Isospin-QMD (IQMD). This model in-cludes the isospin effects in term of symmetry energy andisospin dependent cross sections. The model has beenfound well in explaining the behavior of symmetry en-ergy from 50 to 100 MeV/nucleon[7–16]. The problemwith the results are of opposite nature at sub-saturationas well as supra saturation densities. The work is inprogress to check the validity of results with other dy-namical models.In conclusion, QMD model can explain the various phe-nomena over a long range of incident energy from a fewMeV/nucleon to thousand MeV/nucleon. It is of keen in-terest to check its validity for the determination nuclearequation of state for asymmetric nuclear matter.

∗corresponding author: [email protected]

[1] C. Hartnack, H.Oeschler and J. Aichelin, Phys. Rev.Lett. 96 012302 (2006).

[2] C. Hartnack, H. Oeschler, Y. Leifels, E. L. Bratkovskaya,and J. Aichelin, Phys. Rept. 510 119 (2012).

[3] Y. K. Vermani and R. K. Puri, Phys.Rev. C 79 064613(2009).

[4] R. K. Puri and J. Aichelin, J.Comput.Phys. 162 245(2000).

[5] A. D. Sood and R. K. Puri, Phys. Rev. C 73 067602(2006).

[6] A. D. Sood and R. K. Puri, Phys. Rev. C 70 034611(2004).

[7] C. Hartnack et al., Eur. Phys. J. A1 151 (1998).

[8] M. B. Tsang, Y. Zhang, P. Danielewicz, M. Famiano, Z.Li, W. G.Lynch, and A. W. Steiner, Phys. Rev. Lett.102 122701 (2009).

[9] Z. Q. Feng and G. M. Jin, Phys. Lett. B 683 140 (2010).[10] S. Kumar, Y. G. Ma, G. Q. Zhang, and C. L. Zhou, Phys.

Rev. C 84 044620 (2011).[11] S. Kumar, Y. G. Ma, G. Q. Zhang, C. L. Zhou, Phys.

Rev. C 85 024620 (2012).[12] S. Kumar and Y. G. Ma, Nucl. Phys. A 898 59 (2013).[13] S. Gautam, A. D. Sood, R. K. Puri and J. Aichelin, Phys.

Rev. C 83 034606 (2011).[14] S. Kumar and Y. G. Ma, Phys. Rev. C 86, 051601 (2012).[15] Mandeep Kaur, Varinderjit Kaur, and Suneel Kumar

Phys. Rev. C88,054620(2013)[16] Sakshi Gautam, Phys. Rev. C88,057603(2013)

42

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FUSION14

A new way to study the rotational states built on the Hoyle State

Suresh Kumar,1, ∗ Abhijit Bhattacharyya,1 S.P. Behera,1 R. Kujur,1 Ajay Kumar,1 K. Mahata,1 E.T. Mirgule,1

G. Mishra,1 A. Mitra,1 A. Pal,1 S.K. Pandit,1 A. Parihari,1 P.C. Rout,1 S. Santra,1 A. Shrivastava,1 and V.M. Datar1

1Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India

The study of the Hoyle state is one of the importanttopic in nuclear physics. The 0+

2 state in 12C at 7.65MeV predicted by Fred Hoyle, has an important role inthe production of carbon and heavier nuclei through nu-cleosynthesis. Currently the Hoyle state and its higherrotational member 2+

2 are being investigated by variousgroups. Investigations through different reaction routeshas been carried out which indicates existence of a 2+

2

state at ∼10 MeV [1, 2]. To establish that the 2+2 state

and the Hoyle state have similar structure we populatedthem from preferential decay of resonances which are be-lieved to be highly deformed structures in 24Mg, 20Neand 16O. Their decay via alpha, 8Be and 12C(0+

2 ) emis-sion has been measured and preliminary evidence for thepopulation of the 7.65 and 10 MeV states in 12C is pre-sented here.

The measurement was performed at the PelletronLinac facility, Mumbai using 12C beams of energy rang-ing from 61 to 83 MeV. Two ∆E − E particle identi-fier consist of silicon strip detectors of size 50×50 mm2

and thicknesses 50 & 1500 µm, respectively, were set at15.9 cm from the target. The data were recorded in listmode with a trigger that at least one event has occurredin each telescope. The data were analyzed for the sequen-tial α and 8Be decays of the compound nucleus formed.The data were filtered with appropriate timing and par-ticle identification gates. As the ground state of 8Be isa 92 keV unbound, it is identified by detecting the 2α incoincidence with the expected relative energy.

The kinetic energy (KE) of the undetected recoiling12C was deduced using the energy and position of thethree α-particles in the two telescopes. Thus, the totalKE of the exit channel is calculated and its spectrum isshown in Fig. 1(a). The prominent peaks marked 1 to 4in it are the g.s.; 4.43,2+; 7.65,0+

2 and ∼10 MeV statesof 12C. Assuming the first decay to be 8Be emission, itscentre of mass energy spectra leading to the above fourstates are shown in Fig. 1(b).

An interesting observation noted here that the g.s.,0+ & 4.43, 2+ both are strongly fed through a state∼15 MeV in 16O and the Hoyle & the ∼10 MeV states arestrongly fed through an intermediate state near 20 MeV.

The 20 MeV excitation region of 16O is known to have ahighly deformed and likely to be a linear chain configu-ration [3].

We conjecture here that the Hoyle and the ∼10 MeV

FIG. 1: (a) Total K.E. spectra, peaks corresponds to thestates of 12C and (b) 8Be spectra showing the preferred 16Ostates which α-decay to the final states of 12C.

states both are strongly fed from the highly deformedalpha cluster state in 16O due to their structural similar-ity [4]. Further analysis of the angular correlation of αand 8Be in the present data will hopefully ascertain thespin parity of the ∼10 MeV structure.∗corresponding author: [email protected]

[1] W.R. Zimmerman, M.W. Ahmed, B. Bromberger et.al,Phys. Rev. Lett. 110, 152502 (2013).

[2] M. Itoh, H. Akimune, M. Fujiwara, Phys. Rev. C 84,054308 (2011).

[3] T. Ichikawa, J.A. Maruhn et.al, Phys. Rev. Lett. 107,

112501 (2011).[4] Suresh Kumar, M.A. Eswaran, E.T. Mirgule et.al, Phys.

Rev. C 50, 1535 (1994).

43

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FUSION14

Reaction mechanisms in the 9Be+89Y system

G. S. Li,1, ∗ Y. D. Fang,1 S. Mukherjee,2 M. L. Liu,1 X. H. Zhou,1 Y. H. Zhang,1

N. T. Zhang,1 J. G. Wang,1 B. S. Gao,1 Y. H. Qiang,1 S. Guo,1 and Y. Zheng1

1Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, People’s Republic of China2Physics Department, Faculty of Science, M. S. University of Baroda, Vadodara 390 002, India

The existing fusion reaction measurements for the9Be+89Y system [1] have been extended to higher en-ergies. Five 89Y targets with thickness of ∼1.0 mg/cm2

were bombarded by the 9Be beam delivered by the HeavyIon Research Facility in Lanzhou (HIRFL) at energiesgreater than the fusion barrier. Gold catcher foils wereused along with each target foil to stop the recoiling nu-clei. The beam flux was monitored by the total chargecollected in the Faraday cap placed behind the targets.Ten high-purity germanium (HPGe) detectors were used

0

Co

un

ts

100000

50000

250

E (keV)g

500 750 1000 1250 1500

13

63

.0 k

eV

,T

c9

3g

14

77

.1 k

eV

,T

c9

3g

70

2.6

keV

,T

c9

4g

87

1.1

keV

,T

c9

4g

84

9.7

keV

,T

c9

4g

76

5.8

keV

,T

c9

3g

20

2.5

keV

,Y

90

m

47

9.5

keV

,Y

90

m

FIG. 1: Typical γ-ray spectrum showing γ lines of differentevaporation residues populated for the 9Be+89Y system atthe projectile energy of 48.7 MeV.

to measure the decay γ rays. The typical spectrum forthe off-line measurement is given in Fig. 1. Several iden-tified channels from radioactive decay are denoted in the

spectrum. The experimental evaporation residue crosssections were extracted using their half-lives, prominentγ-ray energy of decay, and intensity listed in Table I [2].Table II shows some preliminary results of cross sectionswith errors of 90Y one neutron transfer reaction prod-uct. Coupled-channels calculations will be carried outand compared with the experimental data. Detailed anal-ysis is in progress.

TABLE I: The physical properties of the populated evapora-tion residues.

Reaction channel Residue T1/2 Eγ (keV) Iγ

3n 95Tcg 20h 765.8 93.8

4n 94Tcg 293m 702.7 99.6

5n 93Tcg 2.75h 1363.0 66.0

α2n-CF/1n-αICF 92Nbm 10.15d 934.5 99.0

1n transfer 90Ym 3.19h 479.5 99.7

TABLE II: The cross section values of one neutron transferresidue 90Y.

Residue Energy (MeV) σ (mb)

90Y 44.2 8.44±0.6890Y 45.7 8.41±0.6790Y 47.3 8.70±0.7090Y 48.7 7.96±0.6490Y 50.1 8.23±0.66

∗corresponding author:[email protected]

[1] C. S. Palshetkar et al., Phys. Rev. C 82, 044608 (2010).[2] Richard B. Firestone, Table of Isotopes, version 1.0 (1996).

44

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FUSION14

Optical model potentials for 6He+209Bi extracted from 208Pb(7Li,6He)209Bi reaction

C. J. Lin,1, ∗ L. Yang,1 H. M. Jia,1 H. Q. Zhang,1 F. Yang,1 Z. D. Wu,1

X. X. Xu,1 Z. H. Liu,1 P. F. Bao,1 L. J. Sun,1 and N. R. Ma1

1China Institute of Atomic Energy, P. O. Box 275(10), Beijing 102413, China

Nucleus-nucleus interaction potential is a basic elementin the research of nuclear physics. With the technical de-velopment of radioactive ion beams (RIBs), study of reac-tion mechanisms involving exotic nuclei has become a hottopic of current interest in recent years because the exoticproperties of such nuclei, like weakly bound, halo struc-ture, etc., may bring about the reaction dynamics compli-cated. An important task is to determine the interactionpotential, in practice the optical model potential (OMP)of the exotic nuclear system. Due to the limits of inten-sity and quality of RIBs, reactions have been studied onlyfor a few systems at a few energies with usually somehowlarge uncertainty of the data obtained. It is rather dif-ficult to accurately extract the OMPs directly from theelastic data. In view of this, an alternative method wasproposed to extract the OMPs of exotic-nucleus systemsin exit channels through transfer reactions [1–3]. In thispresentation, we will take the 6He+209Bi system as anexample to demonstrate this method.

0 30 60 90 120 150 18010-2

10-1

100

101

102

103

c.m. (deg)

42.55 MeV

37.55 MeV 10

32.55 MeV 102

28.55 MeV 103

208Pb(7Li,6He)209Bi25.67 MeV 104

d/d

(m

b/sr

)

PRELIMINARY

FIG. 1: Experimental angular distributions of208Pb(7Li,6He)209Bi compared with CRC resutls.

0.0

0.3

0.6

10 20 30 400

1

2

-V(R

s) (M

eV)

(a)

PRELIMINARY

(b)

-W(R

s) (M

eV)

Ec.m.

(MeV)

FIG. 2: The BTA phenomenon for the 6He+209Bi system.

Angular distributions of the 208Pb(7Li,6He)209Bi one-proton transfer reaction were measured at Elab =25.67, 28.55, 32.55, 37.55, and 42.55 MeV for transfers tothe ground state as well as the first and second excitedstates of 209Bi. Data were analyzed by CRC methodto fit the transfer angular distributions (Fig. 1). TheOMPs for the exotic system 6He+209Bi in the exit chan-nels have been extracted successfully. In the analysis,the 7Li+208Pb OMPs were deduced from elastic scatter-ing data measured in the same experiment. From the ex-tracted OMPs of the 6He+209Bi system, the phenomenonof so-called breakup threshold anomaly (BTA) has beenobserved (Fig. 2). Furthermore, the angular distribu-tions of elastic scattering and total reaction cross sectionsat near- and sub-barrier energies have been calculatedby the extracted OMPs and compared with the resultsof the directly elastic-scattering measurements. Goodagreement has been reached. Details will be presented inthe conference.∗corresponding author: [email protected]

[1] C. J. Lin et al., AIP Conf. Proc. 853, 81 (2006).[2] G. P. An et al., Chin. Phys. Lett. 25, 4237 (2008).

[3] Z. D. Wu et al., Chin. Phys. Lett. 26, 022503 (2009).

45

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FUSION14

Breakup, α-particles production, and fusion suppression in reactions with 7Li

D. H. Luong,1, ∗ M. Dasgupta,1 D. J. Hinde,1 R. du Rietz,1, † R. Rafiei,1, ‡ M.Evers,1 A. Diaz-Torres,2 I. P. Carter,1 K. J. Cook,1 D. Jeung,1 R. Kandasamy,1, §

S. McNeil,1 C. Palshetkar,1 D. Rafferty,1 C. Simenel,1 A. Wakhle,1 and E. Williams11Department of Nuclear Physics, Research School of Physics and Engineering,

Australian National University, Canberra, ACT 0200, Australia2ECT∗, Villa Tambosi, I-38123 Villazzano, Trento, Italy

With the discovery of halo nuclei, and recent intensivedevelopment of radioactive ion beams (RIBs) around theworld, there is renewed interest in studying interactionof weakly-bound light nuclei as a basis for understandinginteractions of halo nuclei and RIBs. Using a novel exper-imental approach applying the concept of experimentalbarrier distribution [1], reactions of the weakly-bound nu-clei 9Be and 6,7Li with heavy targets consistently showedsuppression of complete fusion by ∼30% [2, 3]. The lowthreshold energies for breakup of Li and Be are widelyassociated with their observed suppression of completefusion [1–11], with breakup described as cluster decayfrom unbound states independent of the mechanism thatpopulates it [12–18]. More recent results [19], however,hinted at cluster transfer to be a major contributor tothe suppression of complete fusion in Li.

From our recent sub-barrier coincidence measurementsfor the reactions of 7Li with 144Sm, 207,208Pb and209Bi [20], the exclusive cross-sections for Z=1 and Z=2particles were obtained together with the inclusive cross-section for α-particles (see Fig. 1). The probabilityfor sub-barrier breakup are extracted from these cross-sections and used to predict above-barrier suppressionof complete fusion using the classical trajectory modelPLATYPUS. The results of this study will be presentedand discussed.

∗ corresponding author:[email protected]† Current address: Malmo University, Malmo205 06, Swe-

den.‡ Current address: The University of Western Australia,

Crawley, WA 6009, Australia§ Permanent address: Nuclear Physics Division, Bhabha

Atomic Research Centre, Mumbai 400085, India.[1] M. Dasgupta et al., Phys. Rev. Lett. 82, 1395 (1999).[2] M. Dasgupta et al., Phys. Rev. C 66, 041602(R) (2002).[3] M. Dasgupta et al., Phys. Rev. C 70, 024606 (2004).[4] C. Signorini et al., Eur. Phys. J. A 5, 7 (1999).[5] V. Tripathi et al., Phys. Rev. Lett. 88, 172701 (2002).[6] Y. W. Wu et al., Phys. Rev. C 68, 044605 (2003).[7] L. F. Canto et al., Phys. Rep. 424, 1 (2006).[8] S. Santra et al., Phys. Lett. B 677, 139 (2009).[9] D. H. Luong et al., EPJ Web of Conf. 17, 03002 (2011).

[10] D. H. Luong et al., EPJ Web of Conf. 35, 05007 (2012).[11] P. R. S. Gomes et al., J. Phys. G: Nucl. Part. Phys.

[m

b/sr

/dσd

-110

110

010

(a) Pb208Li +7 , E = 30.0 MeVbeam

exclusive deuteron

exclusive alpha

inclusive alpha Ref. [21]

inclusive alpha

exclusive triton

90

[m

b/sr

/dσd

-110

110

010

100 110 120 130 140 150 160 170 [deg]labθ

(b) Pb207Li +7 , E = 30.0 MeVbeam

exclusive deuteron

exclusive alphainclusive alpha

exclusive triton

FIG. 1. Differential cross-sections for singles and coincidenceparticles produced in the reaction of 7Li with 208Pb and 207Pbboth at beam energy Ebeam = 30.0 MeV. The open circles in(a) are data taken from Hausser et al. [21]

39, 115103 (2012).[12] H. Freiesleben et al., Phys. Rev. C 10, 245 (1974).[13] G. R. Kelly et al., Phys. Rev. C 63, 024601 (2000).[14] R. Ost et al., Z. Phys. 266, 369 (1974).[15] J. L. Quebert et al., Phys. Rev. Lett. 32, 1136 (1974).[16] D. Scholz et al., Nuc. Phys. A 288, 351 (1977).[17] C. Signorini et al., Phys. Rev. C 67, 044607 (2003).[18] A. Shrivastava et al., Phys. Lett. B 633, 463 (2006).[19] A. Shrivastava et al., Phys. Lett. B 718, 931 (2013).[20] D. H. Luong et al., Phys. Lett. B 695, 105 (2011).[21] O. Hausser et al., Phys. Lett. B 38, 75 (1972).

46

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FUSION14

Statistical model calculations for evaporation residue and fission cross-section for210Po nuclei

Ruchi Mahajan,1, ∗ B.R. Behera,1 and Santanu Pal21Department of Physics, P.U Chandigarh-160014

2CS-6/1, Golf Green, Kolkata-700095 (Formerly with VECC kolkata)

Heavy-ion induced reactions are sensitive to entrancechannel of heavy ion forming the compound nucleus, thespin and deformation of the target, the mass of the pro-jectile and the bombarding energy with respect to fu-sion barriers and coupling of various degrees of freedom[1, 2]. For better insight into heavy ion reactions, a de-tailed study of the decay products of the compound nu-cleus (CN), such as evaporation residues (ER) and CNfission fragments (FF) is neccesary. So, in order to havecomplete study of fusion-fission dynamics, fission cross-section and evaporation residue cross-section meausre-ments can be a useful probe.

FIG. 1: Experimental capture cross-section(full dots) for 18O+ 192Os. Dashed line shows no coupling and solid line showscoupling.

In the present work, theoretical calculations for ERand fission cross-section have been performed for 210Popopulated by 18O + 192Os in the excitation energy range52.43 - 83.51 MeV. The experimental data for ER andfission cross-section has been reported in [2]. Spin dis-tribution of the fused system is an important input ofthe statistical model and this can be obtained by fittingthe experimental fusion cross-section by a suitable model.So, to reproduce the experimental fusion cross-sectionCoupled Channel Calculations have been performed us-ing CCFULL [3]. Here, projectile 18O is a vibrator nu-cleus and target 192Os is a rotor. The potential param-eter used in the present Coupled Channel calculationswas chosen by fitting the experimental capture cross sec-

tion and is shown in Fig 1. The fittedvalues are V0 =70.0 MeV, r0 = 1.17 fm and a0 = 0.66 fm, where V0 isthe depth parameter of the Woods Saxon potential, r0is the radius parameter, and a0 is the surface diffusenessparameter.

After fitting, CCFULL gives the spin distribution (forcapture cross-sections) as an output file and this file hasbeen used as an input as the spin distribution of com-pound nuclei for statistical model code to fit the experi-mental ER and fission cross-section. Then, in order to fitthe experimental data for ER and fission cross section,final theoretical calculations were performed using BohrWheeler formalism including shell-corrections in the leveldensity and fission barrier. For reproducing the data, dif-ferent scaling factors (K) in the range 1.0 to 0.7 has beenused. The fitted Fission and ER cross-section is shown inFig 2. The region for the low scaling factor less than one

FIG. 2: Dots are the experimental data and different lines arethe theoretical calculations for different scaling factor, K (asgiven inside the diagram): (a) For Fission cross section (b)ER cross section.

in this mass region warrants for new experimental andtheoretical calculations. Such experiments are alreadyplanned.∗corresponding author:[email protected]

[1] S. Kailas, Phys. Rep.284, 381 (1997).[2] R.J Charity, J.R Leigh, J.J Bokhorst, A. Chatterjee, G.S

Foote, D.J Hinde, J.O Newton, S. Ogaza and D. Ward

Nuclear Physics, A 457, 441 (1986).[3] K. Hagino, N. Rowley, A. T. Kruppa,Comput. Phys. Com-

mun.123, 143 (1999).

47

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FUSION14

Fission barrier of 210Po

K. Mahata1, ∗ and S. Kailas11Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, INDIA

Experimental determination of fission barrier heightcontinues to be challenging problem in nuclear fission.Accurate knowledge of fission barrier height is importantfor understanding the heavy ion induced fusion-fissiondynamics and for the prediction of super heavy elements.Although a number of studies have been made, thereare still ambiguities in choosing various input param-eters for the statistical model analysis. In our earlierstatistical model analysis [1] of fission and evaporationresidue cross-sections along with pre-fission neutron mul-tiplicity data for 12C+198Pt system yielded fission barri-ers much smaller (∼ 13 MeV) than those (∼ 21 MeV)obtained for same compound nuclei from the analysisof light ion induced reactions. In the present study, wehave analyzed the fission excitation functions and fissionfragment anisotropies for p+209Bi, α+206Pb, 12C+198Ptand 18O+192Os systems leading to the same compoundnucleus. Fission barrier is expressed as Bf (J) = cf ×BRFRM

F (J) −∆n + ∆f , where ∆n and ∆f are the shellcorrection at the ground state and saddle configuration,respectively. The angular momentum dependent macro-scopic part of the fission barrier (BRFRM

F (J)) is takenfrom Rotating Finite Range Model [2]. In the earlieranalysis [1], simultaneous fit to fission and ER cross sec-tions along with νpre values for 12C+198Pt system re-quired ∆f to be 0.76×∆n. However, the p and α inducedfission data at lower excitation energies, which are moresensitive to fission barrier height, are compatible with ∆f

=0. Hence, ∆f is assumed to be zero in the further anal-ysis. Fermi gas level density prescription has been usedwith an energy dependent shell correction of the leveldensity parameter as an = an[1 + (∆n/U)(1− e−ηU )] forequilibrium configuration, where an is asymptotic leveldensity parameter and U is available excitation energy.Level density parameter at the saddle configuration (af )is taken as af/an × an. Since, shell correction at thesaddle point is assumed to be zero, there is no excita-tion energy dependence for af . A value of 22 MeV forthe fission barrier is found to reproduce the fission datafor all the entrance channels (see Fig. 1). To the bestof our knowledge, this is for the first time that both thelight and heavy ion induced fission data have been ana-lyzed using the same prescription. However, the presentcalculation with higher fission barrier substantially un-

der predicts the νpre values available for 12C+198Pt sys-tem. Fission fragment angular anisotropies are also sen-sitive to neutron emissions prior to saddle point. Angularanisotropies have been calculated according to the Sta-

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

20 30 40 50 60 70 80 90 100

Pf(%)

E* (MeV)

p

α x0.1

12C x0.01

18O x0.001

0.0

1.0

2.0

45 50 55 60 65

ν pre

12C

FIG. 1: Experimental fission probabilities are compared withstatistical model calculation. The (black) continuous, (green)dotted, (blue) dot-dashed and the (pink) dashed lines arethe statistical model prediction with no shell correction atthe saddle point for p +209Bi, α+206Pb, 12C+198Pt and18O+192Os system, respectively. The (red) continuous lineis the prediction of the statistical model with 70% of groundstate shell correction at the saddle point for α+206Pb sys-tem. The experimental pre-fission neutron multiplicity datais compared with statistical model calculation with no shellcorrection at the saddle point for 12C+198Pt system in theinset.

tistical Saddle Point Model (SSPM) using the statisticalmodel predicted excitation energy and angular momen-tum distributions of the nuclei undergoing fission. Cal-culated angular anisotropy values were found to agreewell with the available experimental data. Effect of pre-equilibrium emission in case of light ion induced reac-tion and contributions of post-saddle and non-statisticalneutron emission to the measured νpre values should befurther investigated.∗corresponding author: [email protected]

[1] K. Mahata et al., Phys. Rev. C 74 041301(R) (2006);K. S. Golda et al., Nucl. Phys. A 913 (2013) 157.

[2] A. J. Sierk, Physical Review C 33, 2039 (1986)

48

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FUSION14

Reaction dynamics studies for the system 7Be+58Ni

M. Mazzocco,1, 2, ∗ D. Torresi,1, 2 L. Acosta,3 A. Boiano,4 C. Boiano,5 A. Diaz-Torres,6

N. Fierro,1 T. Glodariu,7 A. Guglielmetti,8, 5 N. Keeley,9 M. La Commara,10, 4 I. Martel,3

C. Mazzocchi,11 P. Molini,1, 2 A. Pakou,12 C. Parascandolo,1, 2 V.V. Parkar,3 N. Patronis,12

D. Pierroutsakou,4 M. Romoli,4 K. Rusek,13 A.M. Sanchez-Benitez,3 M. Sandoli,10, 4 C. Signorini,1, 2

R. Silvestri,10, 4 F. Soramel,1, 2 E. Stiliaris,14 E. Strano,1, 2 L. Stroe,7 and K. Zerva12

1Dipartimento di Fisica e Astronomia, Universita di Padova, Padova, Italy2INFN - Sezione di Padova, Padova, Italy

3Departamento de Fısica Aplicada, Universidad de Huelva, Huelva, Spain4INFN - Sezione di Napoli, Napoli, Italy5INFN - Sezione di Milano, Milano, Italy

6ECT*, Villazzano (TN), Italy7NIPNE, Magurele, Romania

8Dipartimento di Fisica, Universita degli Studi di Milano, Milano, Italy9Department of Nuclear Reactions, INS, Warszawa, Poland

10Dipartimento di Scienze Fisiche, Universita di Napoli, Napoli, Italy11Faculty of Physics, University of Warsaw, Warszawa, Poland

12Department of Physics and HINP, University of Ioannina, Ioannina, Greece13Heavy Ion Laboratory, University of Warsaw, Warszawa, Poland

14Department of Physics, University of Athens, Athens, Greece

Disentangling the reaction channels induced by lightweakly-bound nuclei at near-barrier energies is gener-ally a rather difficult task. Unambiguous discriminationbetween reaction mechanisms can only be achieved byperforming coincidence measurements of projectile frag-ments, as recently done for the stable weakly-bound nu-clei 9Be [1] and 6,7Li [2, 3]. Despite the still limited Ra-dioactive Ion Beam (RIB) intensities, experiments car-ried out for the 6He [4, 5] and 8He [6] secondary beamsdemonstrated the feasibility of this kind of studies evenfor RIB intensities down to 105 pps.

We studied the interaction of the 7Be RIB (Sα = 1.586MeV) with a 58Ni target at 22.3 MeV beam energy (∼ 1.1VC). The 7Be beam was produced with an intensity ofabout 2-3 × 105 pps by means of the facility EXOTIC [7]at INFN-LNL. We measured for the first time the energyand angular distributions for the 7Be breakup fragments:3He and 4He (see Fig. 1). 4He ions were found 4-5 timesmore abundant than 3He and no 3He-4He coincidenceswere detected. Thus we deduced that nuclear processesother than the breakup channel mostly generate both 3Heand 4He ions.

Detailed kinematical and theoretical calculations fortransfer channels (n-pick, n-stripping, 3He-stripping and4He-stripping) and compound nucleus reactions suggestthat (i) complete fusion accounts for (41 ± 5 %) of the

total reaction cross section extracted from the opticalmodel analysis of the elastic scattering data and that (ii)3He- and 4He-stripping are the most prominent reactionmechanisms among direct processes. More recently, semi-classical calculations with the code PLATYPUS [8] havebeen undertaken in order to investigate possible incom-

FIG. 1: Experimental 3He (red dots) and 4He (black squares)angular distributions and theoretical predictions for the exclu-sive breakup (blue line), n-stripping (pink line) and n-pickup(orange line) processes.

plete fusion contributions to the 3He and 4He productioncross sections.∗corresponding author: [email protected]

[1] R. Rafiei et al., Phys. Rev. C 81, 024601 (2010).[2] D.H. Luong et al., Phys. Rev. C 88, 034609 (2013).[3] A. Shrivastava et al., Phys. Lett. B 718, 931 (2013).[4] J.J. Kolata et al., Phys. Rev. C 75, 031302(R) (2007).[5] J.P. Bychowski et al., Phys. Lett. B 596, 26 (2004).

[6] A. Lemasson et al., Phys. Rev. C 82, 044617 (2010).[7] F. Farinon et al., Nucl. Instrum. Meth. B 266, 4097 (2008).[8] A. Diaz-Torres et al., Comput. Phys. Commun. 182, 1100

(2011).

49

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FUSION14

Fusion of 28Si + 28Si near and below the barrier

G. Montagnoli,1, ∗ A.M. Stefanini,2 L.Corradi,2 S.Courtin,3 E. Fioretto,2 J.Grebosz,4

F. Haas,3 H.M.Jia,2 M.Mazzocco,1 C.Michelagnoli,1 T. Mijatovic,5 D.Montanari,1

C.Parascandolo,1 F. Scarlassara,1 E.Strano,1 S. Szilner,5 D.Torresi,1 and C.A.Ur11Dip. di Fisica e Astronomia, Univ. di Padova, and INFN, Sez. di Padova, Padova, Italy

2INFN, Laboratori Nazionali di Legnaro, Legnaro, Padova, Italy3IPHC, CNRS-IN2P3, Universite de Strasbourg, F-67037 Strasbourg Cedex 2, France

4Institute of Nuclear Physics, Polish Academy of Sciences, PL 31-342 Cracow, Poland5Ruder Boskovic Institute, HR-10002 Zagreb, Croatia

10-4

10-3

10-2

10-1

100

101

102

25 30 35

(2+)2

no coupling

σfu

s (m

b)

Ecm

(MeV)

FIG. 1: Fusion excitation function of 28Si +28Si, compared tothe CC calculations described in the text.

Fusion cross sections of several medium-mass sys-tems [1–3] whose fusion Q-value Qfus is negative, fallbelow the predictions of standard CC calculations far be-low the barrier. Consequently, the astrophysical S-factordevelops a maximum with decreasing energy. This fusionhindrance may have an important impact on the nuclearprocesses occurring in explosive astrophysical scenarios[4, 5], where light heavy-ion systems are involved. It isstill an open question, whether an S-factor maximumshows up at very low energies for these light systemswith Qfus>0, where it is not actually required by sim-ple algebraic considerations. Hence it is very importantto measure the detailed low-energy behaviour for near-by medium-light systems with Qfus>0, because this mayhelp in the extrapolation of the low-energy fusion crosssections for the cases of astrophysical interest.

This contribution presents new recent data for the fu-sion of 28Si+28Si (Qfus=+10.9 MeV). The experimenthas been performed at the XTU Tandem of LNL, usinga 28Si beam at bombarding energies ranging from above

to well below the Coulomb barrier. Evaporation residueshave been detected by the electrostatic separator set-upnear 0, and their angular distributions were measuredat two representative energies around the barrier. Themeasured excitation function is shown in Fig. 1.

0

0.5

1

1.5

2

2.5

3

3.5

4

25 30 35

(2+)2

no coupling

d[ln

(Eσ

)]/d

E (

Me

V-1

)

Ecm

(MeV)

LCS

FIG. 2: Logarithmic derivative of the excitation function of28Si +28Si, compared to CC calculations. LCS (black dots) isthe slope expected for a constant astrophysical S factor.

A preliminary CC analysis of the data has been per-formed, using a Woods-Saxon (WS) potential with stan-dard parameters a=0.63 fm, r0=1.04 fm, V0=73.6 MeV.The radius and depth have been adjusted to fit the datain the barrier region, while the diffuseness is taken fromthe Akyuz-Winther systematics. The collective 2+ stateof 28Si at Ex= 1.779 MeV has been coupled in, and theresult is satisfactory (see Fig. 1). The overall trend of thelogarithmic derivative of the excitation function (Fig. 2),is also reproduced by the calculation, even if the irreg-ularities that appear just below the barrier need furtherinvestigation. We do not observe the hindrance effectdown to the lowest measured cross section ('600 nb).∗corresponding author: [email protected]

[1] C.L. Jiang et al., Phys. Rev. Lett. 89, 052701 (2002);Phys. Rev. Lett. 93, 012701 (2004).

[2] A.M. Stefanini et al., Phys. Rev. C 82, 014614 (2010).[3] M. Dasgupta et al., Phys. Rev. Lett. 99, 192701 (2007).

[4] C.L. Jiang, et al., Phys. Rev. C75, 015803 (2007); Phys.Rev. C 79, 044601 (2009).

[5] L.R. Gasques et al., Phys. Rev. C76, 035802.

50

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FUSION14

Transfer reactions in the 60Ni+116Sn superfluid system at sub-Coulomb energies

D. Montanari,1 L. Corradi,2 S. Szilner,3 G. Pollarolo,4 A. Goasduff,5, 6 E. Fioretto,2 A.M. Stefanini,2 E. Farnea,1 C.Michelagnoli,1, 7 G. Montagnoli,1, 7 F. Scarlassara,1, 7 C.A. Ur,1 S. Courtin,6 F. Haas,6 T. Mijatovic,3 and N. Soic3

1Istituto Nazionale di Fisica Nucleare, I-35131, Padova, Italy2Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, I-35020 Legnaro, Italy

3 Ruder Boskovic Institute, HR-10 002 Zagreb, Croatia4 Dipartimento di Fisica Teorica, Universita di Torino,

and Istituto Nazionale di Fisica Nucleare, I-10125 Torino, Italy5CSNSM, UMR 8609, IN2P3-CNRS, Universite Paris-Sud 11, F-91405 Orsay Cedex, France

6Institut Pluridisciplinaire Hubert Curien, CNRS-IN2P3,Universite de Strasbourg, F-67037 Strasbourg, France

7Dipartimento di Fisica e Astronomia, Universita di Padova, I-35131, Padova, Italy

Transfer reactions have been and are widely used toinvestigate properties of nuclear structure and reactionmechanisms. In particular, the study of two-neutrontransfer reactions is a powerful tool to investigatecorrelations between nucleons in nuclei. In heavy-ionreactions many nucleon transfer channels are available,giving the possibility to compare the relative role ofsingle particle and pair transfer modes [1]. Furthermore,at bombarding energies below the Coulomb barrier,nucleons are transferred in a restricted excitation energywindow and colliding nuclei, being at large internucleardistances, are only slightly influenced by the nuclearpotential. Under these conditions the complexity oftheoretical calculations diminishes and more informationon pair correlations can be extracted from data [2,3].Using the large solid angle magnetic spectrometerPRISMA, at the Laboratori Nazionali di Legnaro(LNL), a first reaction at sub-barrier energies hasbeen performed in inverse kinematics for the closedshell system 96Zr+40Ca [4]. An excitation functionranging from above to well below the Coulomb barrierhas been measured and transfer probabilities [5] havebeen extracted for the neutron transfer channels. Thecomparison between data and microscopic calculationsshows the importance played by transitions to 0+ excitedstates.

We recently performed a similar study at LNL for thesuperfluid system 60Ni+116Sn, in which the groundstate Q-values for one- and two-neutron transfer areclose to zero, matching their optimum Q-value. Twoexperiments have been recently done making use ofPRISMA to detect reaction products. One in inversekinematics to study nucleon transfer excitation functionsand one in direct kinematics where we measured angulardistributions of the neutron transfer channels. In thelast case we could also take advantage of the presence ofthe AGATA demonstrator γ-array to estimate the pop-ulation of excited states in reaction products. In bothexperiments, measurements of transfer cross sectionshave been obtained on the basis of an event-by-eventreconstruction of the ion trajectories inside PRISMA[6] and transfer probabilities have been extracted. Itis therefore interesting to compare the behaviour ofthis transfer mechanism to the previously measuredclosed shell system and to the same kind of theoreticalcalculations.In this talk the results of these recent measurementswill be presented, and a discussion will be made on thepossibilities offered in the field by exploiting large solidangle spectrometers.

[1] R.A. Broglia and A. Winther Heavy Ion Reactions(Addison-Wesley Pub.Co., Redwood City CA, 1991).

[2] B. F. Bayman and J. Chen Phys. Rev. C 26, 1509 (1982)[3] G. Potel, F. Barranco, E. Vigezzi and R. A. Broglia Phys.

Rev. Lett. 105, 172502 (2010)

[4] L. Corradi et al. Phys. Rev. C 84, 034604 (2011)[5] W. von Oertzen and A.Vitturi Rep. Prog. Phys. 64, 1247

(2001)[6] D. Montanari et al. Eur. Phys. J. 47, 4 (2011)

51

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FUSION14

To be announced

K. Morita1

1Kyushu University, Japan

52

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FUSION14

Spin gated GDR widths at moderate temperatures

Ish Mukul,1, ∗ A. Roy,1 P. Sugathan,1 J. Gehlot,1 G. Mohanto,1 N. Madhavan,1 S. Nath,1 R. Dubey,1 N. Saneesh,1

T. Banerjee,1 I. Mazumdar,2 D. A. Gothe,2 Maninder Kaur,3 A. K. Rhine Kumar,4 and P. Arumugam4

1Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India2Department of Nuclear and Atomic Physics, Tata Institute of

Fundamental Research, Homi Bhabha Road, Mumbai 400005, India3Department of Physics, Panjab University, Chandigarh 160014, India

4Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India

Giant dipole resonance (GDR) built on excited stateshas been proven to be an important tool in the study ofnuclear structure as well as reaction dynamics. These res-onances are observed with centroid energies in the rangeof 10-20 MeV which corresponds to frequencies of 1021

Hz, thus making them the fastest known vibrations of amany body system [1]. The behaviour of GDR widthswith spin has been an interesting case and in past fewdecades several experiments have been performed in dif-ferent mass regions to study the width evolution withspin [2–5].

5 10 15 20 250.0

0.5

1.0

1.5

2.0

2.5

3.0

Experiment Total simulation P(M) simulation Low multiplicity component

Cou

nts

(105 )

Fold

FIG. 1: Experimental and simulated fold distribution in 28Si+ 116Cd reaction at 170 MeV beam energy.

We have studied γ ray decay from excited 144Sm using28Si + 116Cd reaction, and extracted GDR widths as afunction of spin. The measurements were performed atdifferent projectile energies in the range of 125 MeV to196 MeV which corresponds to temperature range of 1-2MeV. The 4π spin spectrometer [6] has been coupled withlarge NaI(Tl) detector in these measurements, which wasused to record experimental fold distributions. Modified

fermi function form was chosen for P(M) distribution inthese calculations, and is given by equation

P (M) =2M + 1

1 + exp(M −M0

δM

) (1)

with M0 and δM being two free parameters. Thevariables M0 and δM were varied till resulting spectramatches with the experimental fold spectra [7].

0 10 20 30 40 50 60 70 80 90051015202530354045

Fold 17-18 Fold 19-29

Cro

ss s

ectio

n (a

rb. u

nits

)

Angular momentum ( )

Total Fold 9-10 Fold 13-14

FIG. 2: Spin distribution corresponding to different folds at170 MeV beam energy.

The fold distribution and its corresponding spin distri-bution at 170 MeV beam energy are shown in Fig. 1 and2, respectively. The analysis has been performed usingstatistical model code cascade [8] and thermal shapefluctuation model [9]. In this conference, we would liketo present our findings for spin gated GDR widths overwide range of excitation energy as well as spin.∗corresponding author: [email protected]

[1] K. A. Snover, Annu. Rev. Nucl. Part. Sci. 36, 545 (1986).[2] S. K. Rathi et al., Phys. Rev. C 67, 024603 (2003).[3] S. Bhattacharya et al., Phys. Rev. C 77, 024318 (2008).[4] D. Chakrabarty et al., Nucl. Phys. A 770, 126 (2006).[5] D. R. Chakrabarty et al., Jour. Phys. G: Nucl. Part. Phys.

37, 055105 (2010).

[6] G. A. Kumar et al., Nucl. Instrum. Methods Phys. Res. A611, 76 (2009).

[7] I. Mukul et al., Phys. Rev. C 88, 024312 (2013).[8] F. Puhlhofer, Nuclear Physics A 280, 267 (1977).[9] P. Arumugam et al., Phys. Rev. C 69, 054313 (2004).

53

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FUSION14

To be announced

A. Navin1

1GANIL, France

54

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FUSION14

To be announced

B.K. Nayak1

1BARC, India

55

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FUSION14

To be announced

K. Nishio1

1JAEA, Japan

56

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FUSION14

Study of α-decay of 270Hs∗ using the dynamical cluster-decay model

Niyti,1, ∗ Amandeep,1 Manoj K. Sharma,2 and Raj K. Gupta3

1Department of Physics, Kurukshetra University, Kurukshetra - 136119, India2School of Physics and Materials Science, Thapar University, Patiala - 147004, Panjab, India

3Department of Physics, Panjab University, Chandigarh - 160014, India

Neutron-deficient super-heavy nuclei (SHN) withZ≥101, synthesized via fusion reactions, decay mainlyby alpha emission or in a few cases by spontaneous fis-sion. If a superheavy nucleus possesses high stabilitywith respect to spontaneous fission, only then it will de-cay through other modes such as alpha-decay and, pos-sibly, beta-decay. In fact, the half-lives of different ra-dioactive decays are the experimental signatures of for-mation of SHN in fusion reactions and the calculation ofsuch half-lives are important in identifying decay chainsof SHN. These provide valuable information both on nu-clear structure and nuclear decay mechanisms.

In a recent work [1], half-lives of α-decay chains of289115∗ were calculated by one us, using the PreformedCluster Model (PCM) where fragments are considered tobe in ground state (T=0), like in spontaneous α-decay.The calculated half-lives are found to agree with exper-imental data, but within a constant empirical factor of104. This calls for the posibility of including temperatureT-effects, and hence using the Dynamical cluster-decayModel (DCM) for `=0, since the decay-product (residue)after xn emission, i.e., the SHN has a recoil energy ERassociated with it before the α-decay chain starts.

In the present work we consider α-decay of 270Hs∗formed via hot fusion reaction 226Ra+48Ca after 4n emis-sion [2]. The synthesized SHN, before α-decay occurs,possess recoil energy ER=9-15 MeV which acts like theEc.m. in a reaction. Furthermore, a look at the bindingenergy curve shows that here the target (Z=88) is forcedto undergo fusion reactions leading to the synthesis ofSHN whereas it actually has a tendency to undergo fis-sion, thereby moving the resulting SHN to a region ofeven lower binding energy per nucleon and hence greaterinstability. In accordance with this observation, the de-cay pattern of none of the SHN so synthesized follow anyof the four radioactive decay series thereby emphasizingthe fact that the decay process is not that of naturalradioactivity, but a hot process at `=0 and T 6=0. There-fore, in the following, the α-decay chain(s) of 270Hs∗ areanalyzed by using DCM(`=0) with deformations upto β2

and hot “optimum” orientations of nuclei.In DCM(`=0), or equivalently, PCM(T 6=0), the decay

constant/ half-life time is defined as,

λ = P0ν0P, T12 =

ln2λ. (1)

where P0 and P are the preformation and penetrationprobability, respectively, calculated at R = R1+R2+∆Rfor T-dependent potentials VR(η, T ) and Vη(R, T ). Here,η = (A1 − A2)/(A1 + A2), the mass asymmetry. Theassault frequency for radius of nucleus R0,

ν0 = v/R0 =(2E2/µ)1/2

R0(2)

with E2 = (A1/A)Q. The temperature T (in MeV ) isrelated to excitation energy E∗

CN of compound nucleus,

E∗CN =

110AT 2 − T (MeV ). (3)

For details, e.g., see [1].

TABLE I: DCM(`=0) calculated α-decay half-lives, togetherwith other characteristic properties, for 270Hs∗→266Sg+ α.

T1/2α (Expt.)=7.6+4.9

−2.2 s

P0 P ν0 Half-Life 4R

T1/2α (Cal.)

(MeV) (s) (fm)

T=0.90 0.507 E-9 0.608E-13 0.311E22 7.23 0.779

ER=9

E∗CN=21.15

T=0.84 0.266 E-9 0.104E-12 0.313 E22 8.02 0.784

ER=12

E∗CN=18.15

T=0.96 0.112 E-8 0.279E-13 0.309E22 7.15 0.770

ER=15

E∗CN=24.15

In 226Ra+48Ca reaction at E∗CN=41 MeV, the 270Hs∗

nucleus is formed with the recoil energy range ER=9-15 MeV, which is followed by an α decay populating266Sg with T 1/2

α =7.6 s [2]. We calculate the α-decay half-life, for the first time, at ER=9, 12 and 15 MeV, usingDCM(`=0). The results are given in Table 1. The onlyparameter of model is neck length parameter ∆R. Inter-estingly, the half-life is fitted with in experimental error,in contrast with the results of PCM for α-decay chainsof 289115∗ [1].∗corresponding author : [email protected]

[1] R. Kumar, et al., Phys. Rev. C. 87, 054610 (2013). [2] Yu. Ts. Oganessian,et al., Phys. Rev. C 87, 034605 (2013).

57

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FUSION14

The effect of the recent 17O(p, α)14N and 18O(p, α)15N fusion cross section measurementsin the nucleosynthesis of AGB stars

S. Palmerini1, ∗1INFN - Laboratori Nazionali del Sud, via S.Sofia 62, 95125 Catania, Italy

In recent years, the Trojan Horse Method (THM) hasbeen used to investigate the low-energy cross sections ofproton-induced reactions on A = 17 and A = 18 oxy-gen isotopes [1, 2]. In particular, the strengths of the20 keV and 65 keV resonances in the 17O(p, α)14N and18O(p, α)15N fusion reactions, respectively, have been ex-tracted, as well as the contribution of the tail of thebroad 656 keV resonance in the 18O(p, α)15N reactioninside at astrophysical energies. The strength of the 65keV resonance in the 17O(p, α)14N reaction, measuredby means of the THM, has been used to renormalize thecorresponding resonance strength in the 17O + p radia-tive capture channel. Since the quoted reactions belongto the CNO cycle network for H-burning in stars, thenew estimates of the cross sections have been introducedinto calculations of AGB stars nucleosynthesis [3] to de-termine their impact on astrophysical environments.

Asymptotic giant branch (AGB) stars represent thelast stage in the evolution of low and intermediate massstars (M ≤ 8M) and are responsible of the productionof elements heavier than Fe owing to its characteristicslow neutron capture nucleosynthesis (s-process). More-over, H and He fusion reactions ensure the energy supplyto AGB stars and their alternative burning, coupled withmixing episodes, makes AGB stars a very special site for

the synthesis also of lighter elements, as C, N, F and Al.Moreover AGB stars are surrounded by extended and rel-atively cold envelopes where the ashes of the internal nu-clear fusion reactions condensate in small grains. Thesesolids, once that have been ejected by stellar winds, cometo us as inclusions in meteorites and provide invaluablebenchmarks and constraints for our knowledge of fusionreactions in astrophysical environments. Since in the stel-lar plasma fusion reactions take place at typical astro-physical energies of a few tens of keV, where experimen-tal measurements are extremely difficult, studies on AGBnucleosynthesis have been so far affected by the large un-certainties on reaction rates adopted in the calculations.However, the determination of low energy cross sectionsby the THM overcomes extrapolation procedures and en-hancement effects due to electron screening. As a resultsthe more accurate rates determined for the 18O(p, α)15N,17O(p, α)14N, and 17O(p, γ)18F fusion reactions improvethe agreement between the stellar nucleosynthesis modelsand the oxygen isotopic mix shown by meteoritic grains.Moreover, the high precision of the nuclear physics inputsallows us to state that this kind of grains formed in theenvelope of AGB stars with mass below 1.5M, their iso-topic composition being the signature of low-temperatureproton-capture nucleosynthesis [4].∗corresponding author: [email protected]

[1] La Cognata, M., Spitaleri, C., & Mukhamedzhanov, A.M., ApJ 723 1512 (2010).

[2] Sergi, M. L., Spitaleri, C., La Cognata, M., et al., PhRvC82 032801 (2010).

[3] Palmerini, S., La Cognata, M., Cristallo, S., & Busso, M.,

ApJ 729, 3 (2011).[4] Palmerini, S., Sergi, M. L., La Cognata, M., et al. ApJ

764 128 (2013).

58

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FUSION14

Reaction Mechanisms in the 6Li+52Cr system

Bhawna Pandey,1, ∗ P.M. Prajapati,1 D. Patel,2 V.V. Desai,3 H.Kumar,4

S.V.Suranarayana,3 B.K.Nayak,3 Alok Saxena,3 S.Jakhar,1 C.V.S. Rao,1 and T.K.Basu5

1Fusion Neutronics Laboratory, Institute for Plasma Research, Bhat, Gandhinagar-382428, India2Department of Physics, The M.S.University of Baroda, Vadodara-390002, India

3Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400085, India4Department of Physics, Aligarh Muslim University, Aligarh-202002, India

5Raja Ramanna Fellow of DAE, Institute for Plasma Research, Bhat, Gandhinagar -382428, India

Studies of weakly bound nuclei with intermediate masstarget are of immense importance in Fusion Applica-tions. In the present study the reactions induced byweakly bound 6Li projectile interacting with interme-diate mass target 52Cr are investigated. Calculationsare performed at the near barrier energies ELi−6(lab)= 17.5, 21.5, 25.5, 29.5 and 32.5 MeV. StatisticalModel Calculations (PACE, ALICE)[1] and Continuum-Discretized–Coupled-Channel (CDCC: FRESCO)[2] cal-culations are used as a tool to provide information aboutthe main reaction mechanisms. The theoretical study inthe present work is an important step in the direction tomeasure the cross-section of 55Fe(n, p)55Mn reaction withsurrogate method which is very important from Fusionpoint of view. As light weakly bound stable nucleus (6Li)shows low nucleon separation energies (for 6Li: Q= -1.47MeV for the a + d breakup), it is therefore a good can-didate for important breakup (BU) cross-sections. Thispossibility affects the dynamics of fusion reaction (6Li+52Cr) due to the fact that a part of the incoming fluxmay be lost from the entrance channel before overcom-ing the fusion barrier and, moreover, one of the fragmentsremoved from the projectile may fuse leading to an im-portant InComplete Fusion (ICF) or Transfer Reaction(TR) contribution[3, 4].

FIG. 1: CDCC calculations for the 6Li+52Cr .

In this paper, Light Charged Particle (LCP) energyspectra for 6Li+ 52Cr system and respective contribu-tions of the different reaction mechanisms such as Com-plete Fusion (CF), InComplete Fusion (ICF), TransferReaction (TR), and Break Up (BU) are discussed with

their cross-sections. The processes (different reactionmechanisms) taken into account are the following:

1. 6Li+52Cr → α +d+52Cr (BU)

2. 6Li+52Cr → α +(55Cr)∗ → subsequent decay (d-ICF or d-TR)

3. 6Li+52Cr→ d+(56Fe)∗ → subsequent decay (α -ICF or α -TR)

4. 6Li+52Cr→ 5Li+(52Cr)∗ → subsequent decay (Single ’n’ strip-ping from 6Li)

5. 6Li+52Cr → 5He+(53Mn)∗ → subsequent decay (Single ’p’stripping from 6Li)

6. 6Li+52Cr → (58Co)∗ → subsequent decay (CF)

An illustrative case is shown in Fig.1. The purple, redand blue solid lines represent the total reaction cross-section, fusion and breakup cross-sections respectivelyusing CDCC calculations in FRESCO code. Fig.2.showsthe PACE and ALICE calculations for 6Li(52Cr,d)56Fe∗.This experiment has been proposed at BARC-TIFRPelletron facility Mumbai to measure the cross-sectionof 55Fe(n, p)55Mn reaction with surrogate reaction6Li(52Cr,d)56Fe.The self supporting target of nat-Cr andenriched 52,53Cr are being prepared using various sput-tering technologies as normal rolling does not work dueto its very brittle nature. For 1-3 micron Cr target de-position, we are using sub micron grade polished NaClcrystal as substrate.

FIG. 2: PACE and ALICE calculations for 6Li(52Cr,d)56Fe∗.

∗corresponding author:[email protected]

[1] A Gavron, Phys. Rev. C 21, 230 (1980).[2] I. J. Thompson, Comput. Phys Rep. 7, 167 (1988).[3] Souza, et.al., NPA 821, 36-50 (2009).

[4] Canto, et.al., Phys. Rep. 424, 1 (2006).

59

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FUSION14

Elastic scattering and fusion with 9Be projectile

V. V. Parkar,1, ∗ V. Jha,1 and S. Kailas11Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India

Recently, we have studied the elastic scattering of 9Beon different target systems by using the 8Be+n clus-ter model of 9Be [1]. We have performed Continuumdiscretized coupled channels (CDCC) calculations forbreakup and Coupled reaction channels (CRC) calcula-tions for 1n transfer using FRESCO [2]. The calculationsfor 9Be+28Si system at one energy around barrier alongwith the experimental data are shown in Fig. 1(a). Thesecalculations give good agreement with the data and showthat breakup couplings tend to reduce the elastic cross-sections while the transfer couplings give small increaseat the backward angles. This behaviour is ascribed to theattractive real dynamic polarisation potential (DPP) dueto the breakup and repulsive DPP due to the transfer.This observation is found for wide range of target sys-tems (28Si, 64Zn, 144Sm, 208Pb) at energies around theCoulomb barrier.

We have further tested the efficacy of the 8Be+n clus-ter model in explaining the fusion cross sections for the9Be on different targets (28Si, 89Y, 124Sn, 144Sm, 208Pb)in a wide mass region ranging from the light to the heavytarget. In the CDCC-CRC calculations, the fusion crosssections was obtained as the total absorption cross sec-tion, which is equal to the difference of the total reactioncross section σR and the cross section of all explicitlycoupled direct reaction channels. The short range imagi-nary potentials were used for both fragments-target sys-tem to model the irreversible loss of flux. The calcula-tions for 9Be+28Si system are shown in Fig. 1(b) whichshowed good agreement with the measured data. TheCDCC-CRC calculations were utilized for evaluating thebreakup, transfer and the incomplete fusion (ICF) proba-bilities which show a constant variation at energies abovethe barrier. The systematic behaviour of fusion suppres-sion factors extracted from the experiments for all targetsystems were compared with the calculated ICF proba-bilities.

The details of the calculations and results of both elas-tic scattering and fusion calculations with the availableexperimental data will be presented.

12 14 16 18 20 22 24 26 28 30

σfus (mb)

102

103

9Be+

28Si

Without couplings

TF with Breakup couplings

TF with Breakup + transfer couplings

TF (Data)

Elab (MeV)

VB

20 40 60 80 100 120 140 160

0.4

0.6

0.8

1.0

1.2

9Be+

28Si

12 MeV

θc.m. (deg)

DataWithout couplingsOnly breakup couplings

Breakup+transfer couplings

σ/σ

Ruth

(a)

(b)

FIG. 1: The comparison of (a) measured elastic scatteringdata [4] and (b) measured total fusion (TF) cross sections [5]for the 9Be+28Si system with the coupled channels calcula-tions from 8Be+n model. The calculations without couplings,with breakup couplings, and breakup + transfer couplings areshown by dashed, dash-dot-dot and solid lines respectively.The arrow in (b) refers to the Coulomb barrier VB .

∗corresponding author: [email protected]

[1] V. V. Parkar, V. Jha, S. K. Pandit, S. Santra, and S.Kailas, Phys. Rev. C 87, 034602 (2013).

[2] I. J. Thompson, Comput. Phys. Rep. 7, 167 (1988).[3] V. Jha, V. V. Parkar, and S. Kailas, Submitted to Phys.

Rev. C[4] M. Hugi et al., Nucl. Phys. A 368, 173 (1981).[5] K. Bodek et al., Nucl. Phys. A 339, 353 (1980).

60

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FUSION14

Fusion of 7Li with 124Sn from online and offline gamma ray measurement technique

V. V. Parkar,1, ∗ A. Shrivastava,1 K. Mahata,1 S. K. Pandit,1 P. K. Rath,2 R. Palit,3 S. Santra,1 and V. Jha1

1Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India2Department of Physics, M. S. University of Baroda, Vadodara - 390002, India

3Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai - 400005, India

Recently the fusion studies with stable weakly boundnuclei (6,7Li, 9Be, and 10,11B) on various mass targets hasgiven some interesting conclusions about systematics offusion suppression factor [1]. In continuation of this ac-tivity, we have recently carried out measurement of fusioncross-sections for 7Li+124Sn reaction by online gammaray technique at energies around the Coulomb barrier.The dominant evaporation residues (ER) from completefusion (CF) are 126−128I (3n-5n). Since all these residuesare odd-even nuclei, the total cross-section for the par-ticular ER was extracted by adding all the gamma-raycross-sections feeding the ground state of that ER. Hence,there is slight unambiguity in measured cross-sections be-cause of incomplete level scheme as well as weak feedingtransition strengths.

TABLE I: List of identified residues in the 7Li+124Sn reactionalong with their radioactive decay [2] half-lives (T1/2), γ-rayenergies and intensities following their decays.

Reaction ER T1/2 Eγ (keV) Iγ (%)

124Sn(7Li,3n) 128I 24.99 min 442.9 12.6526.6 1.2

124Sn(7Li,5n) 126I 12.93 d 388.6 35.6753.8 4.2

124Sn(t,1n) 126Sb 12.35 d 414.7 83.3573.9 6.7593.2 7.5720.7 53.8856.8 17.6

124Sn(t,3n) 124Sb 60.20 d 602.7 97.81690.97 47.6

124Sn(7Li,6Li) 125Sn 9.52 min 331.94 97.3124Sn(7Li,8Li) 123Sn 40.06 min 160.32 85.7

In addition to the online gamma ray measurement,we have also measured the ER cross-sections by offlinegamma counting in separate experiment for few energiesaround barrier. In Table 1, the ERs along with their de-cay half lives are listed. The offline gamma measurementat few energies was performed for unambiguous extrac-tion of these residues. In Fig. 1, we have shown thecomparison of ER cross-sections from two methods alongwith statistical model predictions. As can be seen fromthe figure, there is slight normalisation required for online

data.7Li+

124Sn

Online and Offline Data Comparison

Elab (MeV)

20 25 30 35

σER (mb)

100

101

102

103

104 3n (Online)

5n (Online)

3n (PACE)

5n (PACE)

5n (Offline)

3n (Offline)

FIG. 1: Comparison of ER cross-sections from online andoffline gamma measurements in 7Li+124Sn reaction. The linesare from the statistical model calculations.

FIG. 2: The measured complete-fusion cross sections (solidcircles) along with the uncoupled (dotted line) and the cou-pled (dashed line) calculations from CCFULL.

After addition of all neutron evaporation channels, thetotal fusion cross-section was extracted and shown in Fig.2 along with coupled channels calculations done usingCCFULL code. The details of the experimental setup,ER extraction procedure, determination of fusion cross-sections, calculations and results will be presented.∗corresponding author: [email protected]

[1] V. V. Parkar et al., Phys. Rev. C 82, 054601 (2010). [2] http://www.nndc.bnl.gov/nudat2/

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FUSION14

Investigation of transfer in triggering breakup in the reaction of 6Li with 208Pb, 209Bi

D. Patel,1 S. V. Suryanarayana,2 S. Mukherjee,1 B. K. Nayak,2 and J. Lubian3

1Physics Department, Faculty of Science, M. S. University of Baroda, Vadodara-390002, India2Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India

3Instituto de Fisica, Universidade Federal Fluminense,Avenida, Niteroi, R. J. 24210-340, Brazil

Recently, a great deal of attention has been given tothe breakup channel in the nuclear reaction studies withweakly bound nuclei [1]. The observed enhancementand/or suppression in the fusion cross sections at aroundthe Coulomb barrier are associated with the breakup andalso other reaction channels such as transfer (pickup/stripping), which trigger the projectile breakup [2]. Forexample the weakly bound projectile 6Li may directlybreakup into two fragments (d + α) or the breakup mayoccur after some nucleon transfer (pickup/ stripping).

FIG. 1: Relative contribution of direct breakup and 1n-stripping channel in the reaction of 6Li with 208Pb, 209Bi

In a very recent experimental study involving sta-

ble weakly bound projectile (6Li) [2] the 1n-stripping isfound more preferable channel leading to (p + α) andthe contribution from 1n,1p-pick up is found negligibleat below barrier energy in the reaction with 207,208Pband 209Bi targets. In the present work, a theoretical in-vestigation has been carried out using CDCC and CRCformalism, to understand above experimental data quan-titatively. Simultaneous calculations for breakup and 1n-transfer are carried out using Fresco code [3]. All theresonant states of 6Li with finer binnings and maximumexcitation energy upto ∼ 8.5 MeV are included in theCDCC calculations. Also, the target spin is set to 1/2−

to reduce the computing time. The calculations are car-ried out at 26.5 and 29.0 MeV laboratory energies. Inthe 1n-stripping calculation coupling to ground state isconsidered and no target inelastic states are included asthe coupling to target inelastic states give negligible crosssections. The binding energies for core and valence par-ticles are taken as 0.1MeV and the spectroscopic ampli-tudes are set at 2.0. This tuning is done to simulate theneutron stripping from unbound states of 6Li [4].

Fig. 1 shows the results of present calculations (pink)with the inclusion of breakup as well as 1n-strippingchannels and are compared with the experimental datareported by Luong et al.,[2]. From the Fig. 1 a quitereasonable agreement is observed between the presentcalculations and the experimental results. The detailedcalculations are being carried out and the results will bepresented in the conference.

[1] L. F. Canto et al., Phys. Rep. 424, 1 (2006).[2] D. H. Luong et al., Phys. Rev. C 88, 034609 (2013).[3] I. J. Thompson, Comput. Phys. Rep. 7, 167 (1988).

[4] N. J. Davis et al., Phys. Rev. C 69, 064605 (2004).

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FUSION14

A model for explanation of fusion suppression using classical trajectory method

C. K. Phookan1, 2, ∗ and K. Kalita2

1Dept. of Physics, Haflong Govt. College, Haflong, India - 7888192Dept. of Physics, Gauhati University, Guwahati, India - 781014

A two dimensional classical trajectory model is usedto explain the projectile breakup and above barrier fu-sion suppression for the reactions 6Li+209Bi, 6Li+152Smand 6Li+144Sm [1, 2]. For obtaining the initial condi-tions of the equations of motion, a simplified model ofthe 6Li nucleus has been proposed. The two postulatesof the model are : (a) The total energy is equal to thebreakup threshold energy (binding energy) of the 6Li nu-cleus, and (b) The total angular momentum of rotationof the deuteron and α-particle about an axis through itscentre of mass is equal to

√I(I + 1)~ ,where, I is the

spin quantum number of the 6Li nucleus. In the abovemodel, the distance of separation between the deuteronand the α-particle constituting the 6Li cluster is foundto be 2.27 fm.

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5 3

Bre

akup

Fra

ctio

n (B

i)

Impact Parameter (fm)

6Li+144Sm (32 MeV)

Bezier fit

FIG. 1: Breakup fraction (Bi) vs impact parameter at 32 MeV for6Li+144Sm.

Numerical solutions of the equations lead to classifica-tion of orbits into breakup and no-breakup trajectories.The breakup fraction (Bi) is studied as a function ofthe impact parameter. Using quantum mechanical ar-guments, the cutoff impact parameter for fusion is de-termined by proposing a sharp cutoff model [3] whichassumes that there is an angular momentum limit to fu-sion. We introduce a simple formula for explanation of

fusion suppression, according to which fusion suppressionis given by the average of the breakup fractions (Bi) eval-uated at impact parameters ranging from head-on colli-sion up to the cutoff impact parameter with weightagegiven by the fusion probability (Pi).

Fusion Suppression =∑

iBiPi∑i Pi

(1)

The breakup fraction for 6Li+144Sm at 32 MeV isshown in Fig. 1. Using the formula introduced above andthe cutoff impact parameter (4.27 fm), we determine thefusion suppression to be 0.314 which is in agreement withthe experimental value of 0.326. In Fig. 2, we show thecalculated fusion cross section [σcal = σtheo (1-fcal)] for6Li+144Sm at various energies using the calculated fusionsuppression values (fcal). We find that there is excellentagreement between the experimental fusion cross section(σexp) and the calculated fusion cross section (σcal). Sim-ilar analysis for the systems 6Li+209Bi and 6Li+152Smare done, and we find good agreement between the exper-imental (σexp) and calculated fusion cross section (σcal).

200 250 300 350 400 450 500 550 600 650 700 750

28 29 30 31 32 33 34 35 36 37 38 39

σ(m

b)

Ecm(MeV)

σexp

σcal

FIG. 2: Calculated and experimental fusion cross section for6Li+144Sm at different energies.

∗corresponding author: [email protected]; Permanentaddress:Flat No. 2D, Barua Enclave, Guwahati-781024

[1] C. K. Phookan, K. Kalita, Journal of Physics G : Nuclearand Particle Physics 40, 125107 (2013).

[2] K. Hagino, M. Dasgupta and D. J. Hinde, Nucl. Phys. A738, 475 (2004).

[3] E. F. Aguilera and J. J. Kolata, Phys. Rev. C 85, 014603(2012).

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FUSION14

To be announced

J. Piot11GANIL, France

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FUSION14

Trojan Horse particle invariance in fusion reactions

R.G. Pizzone,1, ∗ C. Spitaleri,1, 2 M. La Cognata,1, 2 L. Lamia,1, 2 R. Sparta,1, 2

C.A. Bertulani,3 A.M. Mukhamedzhanov,4 L. Blokhintsev,5 and A. Tumino6

1Laboratori Nazionali del Sud-INFN, Catania, Italy2Dipartimento di Fisica e Astronomia, Universita degli studi di Catania, Catania, Italy

3Texas A&M University Commerce, Commerce, USA4Texas A&M University, College Station, USA

5Institute of Nuclear Physics, Moscow State University, Russia6Universita Degli studi di Enna Kore, Enna, Italy

Trojan Horse method plays an important part for themeasurement of several charged particle induced reac-tions cross sections of astrophysical interest. In order tobetter understand its cornerstones and the related appli-cations to different astrophysical scenarios several testswere performed to verify all its properties and the possi-ble future perspectives. The Trojan Horse nucleus invari-ance [1] for the binary reactions d(d,p)t, 6,7Li(p,α)3,4Hewas therefore tested using the appropriate quasi freebreak-ups, respectively. In the first cases results from 6Liand 3He break up were used, while for the lithium fusionreactions break-ups of 2H and 3He were compared. The

astrophysical S(E)-factors for the different processes werethen extracted in the framework of the Plane Wave Ap-proximation applied to the different break-up schemes.The obtained results are compared with direct data aswell as with previous indirect investigations [2]. Thevery good agreement between data coming from differentbreak-up schemes confirms the applicability of the planewave approximation and suggests the independence ofbinary indirect cross section on the chosen Trojan Horsenucleus also for the present cases. Moreover the astro-physical implications of the results will also be discussedin details.

∗corresponding author: [email protected]

[1] R.G. Pizzone et al., Phys. Rev. C 83, 045801 (2011).[2] R.G. Pizzone et al., submitted to Phys. Rev. C (2013).

65

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FUSION14

Effect of breakup couplings on fusion for 6,7Li+24Mg systems

M.K. Pradhan,1, ∗ A. Mukherjee,1 and B. Dasmahapatra1, †1Nuclear Physics Division, Saha Institute of Nuclear Physics, Kolkata-700064, India

The effect of breakup of weakly bound nuclei on fu-sion has been investigated extensively both experimen-tally and theoretically over the last years. Experimentalworks discuss mainly by comparing the measured fusionexcitation functions to either realistic theoretical predic-tions which do not include couplings to the breakup chan-nels or to the measured fusion excitation functions ofstrongly bound nuclei for which breakup is expected tobe weak [1]. In this context, by considering the couplingsto the breakup channels in the continuum discretizedcoupled channels (CDCC) method, fusion cross sectionscalculations were obtained for the systems 6,7Li+16O,6,7Li+59Co and 209Bi targets [2, 3]. For the 6,7Li+16Osystems, the predictions agree well with the γ-ray mea-surements and no significant effect of breakup on fusionwas observed. Whereas for the 6,7Li+59Co and 209Bi sys-tems, it was found that the breakup enhances the totalfusion at energies just around the barrier, but it hardlyaffects the total fusion at energies well above the barrier.So, in order to contribute in this field, here we presentthe fusion cross sections calculations by considering thebreakup couplings for the 6,7Li+24Mg systems for whichwe had the measured total fusion excitation functionsobtained from the γ-ray method [4].

FIG. 1: Calculated and measured fusion cross sections for the6Li+24Mg system.

The fusion calculations were carried out in the CDCCmethod by the cluster-folding model for 6Li and 7Li usingthe code FRESCO [5]. The method used is similar to thatdescribed in Keeley et al [2]. The binning scheme used todescribe the breakup continuum for 6Li and 7Li is similarto that as described in Kelley et al [6].

FIG. 2: Calculated and measured fusion cross sections for the7Li+24Mg system.

For 6Li, couplings were included to the 1+, 2+, 3+

resonances and the L =0,1,2 α-d continuum. For the7Li, couplings were included to the 1/2− first excitedstate, the 7/2− and 5/2− resonances and the L =0,1,3α-t continuum. The calculations were carrierd out for Li-bombarding energies from above barrier to below barrierenergies in steps of 2 or 1 MeV. The total fusion crosssections thus obtained in the CDCC method are com-pared with the measured total fusion excitation fuctionsin Figs. 1 and 2. We found that the predictions agreewell with the measurement for 7Li+24Mg. Whereas, for6Li+24Mg, agreement is found at below barrier and atwell above barrier energies but at above barrier energies,it is not clear. Details will be presented during the con-ference.∗corresponding author: [email protected]

†retired Professor

[1] L.F. Canto et al., Phys. Rep. 424, 1 (2006).[2] N. Keeley et al., Phys. Rev. C 65, 014601 (2001).[3] A. Diaz-Torres et al., Phys. Rev. C 68, 044607 (2003).[4] M. Ray et al., Phys. Rev. C 78, 064617 (2008).

[5] I.J. Thompson, Comput. Phys. Rep. 7, 167 (1988).[6] G.R. Kelley et al., Phys. Rev. C 63, 024601 (2000).

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FUSION14

Fragment emission studies in low energy light ion reactions

T. K. Rana,1, ∗ C. Bhattacharya,1 S. Manna,1 V. Srivastava,1 K. Banerjee,1 S. Kundu,1 P.Roy,1 R. Pandey,1 A. Chaudhuri,1 T. Roy,1 T.K. Ghosh,1 G. Mukherjee,1 S. Bhattacharya,1

J.K. Meena,1 S. K. Pandit,2 K. Mahata,2 P. Patale,2 A. Shrivastava,2 and V. Nanal31Variable Energy Cyclotron Centre,1/AF, Bidhan Nagar, Kolkata -700064, India

2Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India3Tata Institute of Fundamental Research, Mumbai - 400005, India

Study of fragment emission mechanisms for lightheavy-ion (Aproj. + Atarget ≤ 60) collisions, at energies (≤ 10 MeV/u ) is subject of great interest for many years[1]. The origin of these fragments extends from quasi-elastic, deep-inelastic transfer and orbiting, to fusion -fission processes. For reactions involving α-clustered nu-clei, e.g, 20Ne + 12C, 24Mg + 12C, 28Si + 12C etc. , en-hancement in the yield and/or resonance-like excitationfunction in a few outgoing channels (around the entrancechannel) have indicated the role played by deep inelas-tic orbiting process in fragment emission. Isotopic yieldof fragments is considered to be an important tool tostudy such entrance channel effects; however, such dataare scarce at low energies.

0

10

20

30 40 50 60 700

20

40

60

80

12C + 12C13C + 13C

7Be

9Be

0

20

40

Energy (MeV)

10 20 30 40 50 60

Co

unts

0

20

40

6Li

7Li

FIG. 1: Typical energy spectra of emitted isotopes of Li andBe in the reactions 12C +12C and 13C + 12C.

Here we report our measurement of fragment emissionsin 12C (80 MeV) on 12C and 13C (78.5MeV) on 12C re-actions. The present experiment has been done with themotivation to see if there is any isotopic dependence offragment yield in these two reactions.

The experiment have been performed at Pelletron-Linac facility, Mumbai, using 80 MeV 12C and 78.5 13Cion beams on 12C target ( ∼70µg/cm2). The emittedfragments have been identified using two telescopes, eachconsisting of ∼ 50µm ∆E single-sided silicon strip de-

tector (SSSD) and ∼1030µ E double-sided silicon stripdetector (DSSD) and backed by four CSI(Tl) detectors,each of thickness 6 cm. Inclusive energy distributions forthe various fragments (3 ≤ Z ≤ 5) have been measured inthe angular range of 140 to 360. Typical inclusive energydistribution (θlab = 140 ) of different isotopes of the frag-ments Li, and Be obtained in the reactions 12C +12C and13C + 12C have been shown in Fig. 1 by solid and dottedlines respectively. The angular distributions of differnt

6Li

0.0

0.5

1.0

1.5

7Li

20 40 60

dσ/σ/ σ/σ/

dΩΩ ΩΩ

(m

b/s

r)

0.0

0.5

1.0

1.5

7Be

0.0

0.5

9Be

θθθθcm

20 40 600.0

0.5

1.0

1.5

12C + 12C13C + 12C

FIG. 2: Center of mass angular distribution of different frag-ments for 12C (80 MeV) + 12C (solid circle) and 13C (78.5MeV) + 12C (solid triangle) reactions. The solid line (red)are the corresponding fit with 1/sinθc.m.

isotopes of Li and Be obtained in the above two reactionshave been shown in Fig. 2. The angular distribution ofall the fragments emitted are found to follow 1/sinθc.m

dependence in c.m. frame ( shown by solid lines (red)in Fig. 2 ), which is a characteristics of fission like decayof compound nucleus. It is seen from Fig. 2 that, theangular distribution of 6Li , 7Li and 7Be obtained in 12C+ 12C reactions are more than those obtained in 13C+12C reaction except for 9Be. This may be due to themost probable exit reaction channel, i. e. 25Mg splittinginto 9Be + 16O, in case of 13C + 12C reaction. Furtheranalysis is in progress.∗corresponding author: [email protected]; Permanent ad-

dress:Variable Energy Cyclotron Centre, Kolkata 700064, India

[1] S. J. Sanders etal ., Phys. Rep. 311, 487 (1999).[2] S. Kundu etal ., DAE Symp. On Nucl.Phys. 55, 326(2010).

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FUSION14

Average angular momentum for fusion of 7Li+165Ho

Sarla Rathi1, ∗ and K. Mahata2, †

1Physics Department, VES College of Arts, Science & Commerce, Chembur, Mumbai 712Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085

Fusion involving weakly bound stable and radioactivenuclei is a topic of current interest [1]. Aguilera et al. [2]has recently proposed an analytical model for fusion ofhalo and weakly bound system, which is is an extensionof the Wong model [3]. Wong model which was actuallyproposed for reaction cross-section, has been extensivelyused to analyze fusion data and extract fusion barrier pa-rameters for systems involving tightly bound nuclei, asfusion is the dominant part of the reaction cross-section.However, in case of systems involving weakly bound nu-clei, contribution of direct reaction channels to the reac-tion cross section are significant. Hence, application ofWong model to fit fusion excitation functions to extractbarrier parameters may lead to ambiguous results. Ac-cording to the new analytical model [2], the fusion crosssection is expressed as

σfus =π

k2

∞l=0

(2l + 1)TlPl. (1)

The above expression is same as the Wong model expres-sion with Pl = 1 for all l values. In the analytical modelit is assumed that Pl = 1 for l ≤ Lf and Pl = 0 forl > Lf . This means only partial waves with l less thanor equal to Lf (angular momentum limit to fusion) willcontribute to fusion cross section. Aguilera et al [2] haveanalyzed fusion data for several systems involving weaklybound stable / radioactive nuclei using the above men-tioned analytical model and have extracted values of cut-off angular momentum, Lf . This assumption of having acut-off angular momentum for fusion can be also verifiedby comparing it with the average angular momentum forfusion. In the present work we have compared averageangular momentum of fusion from the analytical modelwith the extracted average angular momentum from themeasured gamma ray multiplicity, ratio of partial evap-oration residue and fit to the fusion excitation functionfor 7Li+165Ho system. Balantekin and Reimer has givena prescription to calculate average angular momentumfrom the fit to fusion excitation [4]. This prescription hasbeen used to calculate average angular momentum andthey are found to be in good agreement with the average

angular momentum obtained from multiplicity data forsystems involving tightly bound nuclei [5]. Good agree-ment has been also found between the average angularmomentum extracted from the fit to the fusion excita-tion function and the multiplicity data for weakly bound

0

5

10

15

20

15 20 25 30 35 40 45

<L>

− h

Ec.m.

FusionFold

ERAnalytic

FIG. 1: The average angular momentum from gamma raymultiplicity (fold) , ratio of evaporation residue (ER) and fitto fusion excitation function (solid line) are compared withthose extracted from the analytical model for 7Li+165Ho sys-tem.

projectile 7Li on 165Ho target [6]. In Fig. 1, the av-erage angular momentum from gamma ray multiplicity,ratio of evaporation residue [6] and fit to fusion excita-tion function are compared with those extracted from theanalytical model. The average angular momentum cal-culated from the Lf of the analyical model is found to belower than the measured average angular momentum.

[email protected][email protected]

[1] E. F. Aguilera et al., Phys. Rev. Lett. 107, 092701 (2011).[2] E. F. Aguilera et al., Phys. Rev. C 85, 014603 (2012).[3] C. Y. Wong, Phys. Rev. Lett. 31, 766 (1973)[4] A. B. Balantekin et al., Phys. Rev. C 33, 379, (1986).

[5] C. V. K. Baba, Nucl. Phys. A553 (1993) 719c.[6] V. Tripathi et. al., Phys. Rev. Lett. 88, 172701 (2002).

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FUSION14

Breakup phenomena study in 7Li+208Pb reaction using 8PLP

P. K. Rath1, E. Vardaci for the FIESTA and EXOTIC collaboration1, ∗1Department of Physics and INFN, Complesso Universitario di Monte S.Angelo, via Cinthia, I-80125 Napoli, Italy.

Study of fusion reactions involving weakly bound (sta-ble or radioactive) projectiles is a subject of topical in-terest [1, 2]. In case of loosely bound nuclei, projectilebreakup modifies the accepted picture for two-body fu-sion of strongly bound nuclei.

FIG. 1: Experimental two-dimensional particle spectra for7Li+208Pb reaction at 31 MeV. The telescope was at forwardangle (θ=20.60,φ=346.530). Deuterons and tritons of differ-ent energies are clearly seperable and are expected to belongto different types of breakup. Different peaks in the tritonband indicates different emission process, including breakupvia inelastic excitation.

Some of the loosely bound projectiles are 6,7Li and 9Be,where the α separation energies are Sα=1.48, 2.45 and1.57 MeV respectively. Projectile breakup can occur innuclear collisions if a state above the relevant breakupenergy threshold is populated. Some observations showthat the majority of prompt breakup events are triggeredby transfer of a neutron from 6Li (neutron stripping) andof a proton to 7Li (proton pick-up)[3, 4]. Our currentstudy has the purpose to investigate the 7Li breakup atenergies around the breakup threshold. The experimentwas performed with a highly efficient and sophisticated4π array 8πLP [5, 6]. We studied the different types ofparticle emitted in the reaction 7Li+208Pb around theColoumb barrier energies, same as in[7]. The case of7Li is however more interesting as 7Li has one boundexcited state below the breakup threshold whereas 6Lihas none. An experimental E-∆E spectrum is shown inFig.1. Different energy peaks are clearly visible for bothdeuterons and tritons. The different patterns on the tri-ton band may indicate the strong presence of the pro-jectile breakup into an α particle and a triton. Particle-particle coincidences were measured to gain insight onthis point and the preliminary results of the analysis willpresented. This same analysis is expected to provide aninterpretation for the broad α spectrum visible in Fig.1.

∗corresponding author: [email protected]

[1] S. Santra et. al. Phys. Rev. C 83, 034616 (2011).[2] P. K. Rath et. al. Phys. Rev. C. 88, 044617 (2013).[3] R. Rafiei et. al. Phys. Rev. C 81, 024601 (2010).[4] D. H. Luong et. al. Phy.Lett. B 695, 105 (2011).

[5] E. Vardaci et. al. Phy.of Atomic Nuclei, 66, 1182 (2003).[6] A. Di Nitto et. al. Eur. Phys. J. A , 47, 83 (2011).[7] C. Signorini et. al. Phys. Rev. C. 67, 044607 (2003).

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FUSION14

Quasifission and fission timescale: Zeptosecond versus attosecond

A.Ray,1, ∗ A.K.Sikdar,1 and A. De2

1Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata -700064, India2Raniganj Girls’ College, Raniganj, Bardhaman 713358, West Bengal, India

Although both the fission and quasifission processeshave been known for a long time [1], recently a contro-versy [2] has developed regarding the time scales of thesenuclear processes. Model-dependent measurements of fis-sion timescales based on prescission neutron emission [3]and the giant dipole resonance [4] give longer lifetimes∼ (10−20−10−21) sec for the highly excited uranium-likecomplexes compared to the expectations from Bohr andWheeler theory [1]. It has been interpreted as due to theviscosity of nuclear matter slowing down the fission pro-cess. However recent measurements of the timescales ofthe fission and quasifission processes by nuclear model-independent crystal blocking technique [5] and atomicX-ray technique [6] suggest timescales ∼ 10−18 sec forsimilar systems requiring unrealistically large viscosityparameter. Recently R. du Rietz et al. [2] measuredmass-angle distributions of quasifission fragments fromthe reactions of 48Ti and 64Ni with tungsten at (5-6) MeV/A bombarding eneregies and obtained quasifis-sion timescales ∼ (10−20 − 10−21) sec by parametriz-ing nuclear sticking time distribution with half Gaus-sians followed by exponential decay. We find from 2Dcolor scatter plot [2], that dσ/dθc.m. ∝ exp(−θc.m./γ)for large values of θc.m.. The result implies exponen-tial decay of an ensemble of classical dinuclear systemsN = N0e

−λt rotating through an angle θrot in time t,where θrot = (L/I)t (L being angular momentum andI the moment of inertia of the dinuclear system) andγ = L/λI. So the zeptosecond lifetime of quasifissionprocess as obtained in ref [2] depends on a classical pic-ture of an ensemble of rotating dinuclear systems under-going exponential decay in zeptosecond timescale afterits creation. Andersen et al. measured [7] lifetimes ofsimilar quasifission reactions 74Ge and 58Ni with tung-sten at (5-6) MeV/A bombarding eneregies by crystalblocking technique and obtained lifetime ∼ 10−18 sec.So the methods that do not use any nuclear model todeduce the nuclear lifetime seem to give lifetime ∼ 10−18

sec, whereas the methods that depend on nuclear models

give lifetime of the fission/quasifission processes ∼ 10−21

sec.

We think a quantum mechanical description of the de-cay process is required to explain the controversy. It isknown that the unitary reversible quantum mechanicaltime evolution of unstable states does not lead to irre-versible exponential decay. Quantum mechanics predictsan approximately flat initial survival probability of theensemble of dinuclear systems when the quantum coher-ence of the decaying unstable states(i.e. the linear super-position of the decaying dinuclear state and its fragment)is maintained. Considering the quantum mechanical timeevolution of the dinuclear state |ψt >= e−iHt|ψt=0 >, theaverage angle of rotation < φt > in time t varies as t2. Ifwe take H as rigid body rotational Hamiltonian ,< φt > isindependent of time. Hence classical rotation of the din-uclear system in zeptosecond timescale should not takeplace unless quantum coherence is lost in zeptosecondtimescale. The quantum coherence is lost when the firstnatural measurement of whether decay occured or notwas recorded through the interaction of the system withthe environment. We think the atomic K-X-ray emissionin 10−18 sec timescale is the first evidence recorded inthe atomic structure regarding whether fission had oc-curred. So the quantum decoherence time scale of thenucleus undergoing quasifission or fission should be ofthe order of 10−18 sec and hence the extraction of decaytimescale assuming classical rotation and exponential de-cay of the dinuclear system in zeptosecond timescale isprobably not justified. So the actual timescale of decay-ing nucleus should be = Quantum decoherence time +exponential decay timescale ≈ 10−18 sec + 10−21 sec ≈10−18 sec as obtained from nuclear model-independentcrystal blocking and X-ray techniques. The controversyregarding quasifission/fission timescale is probably dueto the application of classical rotation and decay in zep-tosecond timescale when the decaying nucleus is still ina state of quantum superposition.∗corresponding author: [email protected]; Permanent ad-

dress:1/AF, Bidhannagar , Kolkata -700064

[1] Treatise on Heavy-Ion Science, vol 2, ed. D.A. Bromley,Plenum Publishing (N.Y.), 1984.

[2] R. du Rietz et. al., Phys. Rev. Lett. 106, 05271 (2011).[3] D.J. Hinde et.al., Phys. Rev. C 45, 1229 (1992).[4] P. Paul and M. Theonessen, Ann. Rev. Nucl. Part. Sci.

44, 65 (1994).[5] F. Goldenbaum et. al., Phys. Rev. Lett. 137, 5012 (1999).[6] J. D. Molitoris et. al., Phys. Rev. Lett. 70,5 (1993).[7] J. U. Andersen et. al., Phys. Rev. Lett. 99, 162502 (2007).

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FUSION14

Multinucleon Transfer Study in 58Ni,56Fe(12C,X); X:11C, 11,10B, 10,9,7Be, 8Begs, and 7,6Liat E(12C)= 45 and 60 MeV

B.J. Roy,1, ∗ A. Parmar,2 V. Jha,1 D.C. Biswas,1 Biraja Mohanty,3 M. Oswal,3 A. Jhingan,4 and T. Nandi41Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085

2Dept. of Physics, Sardar Patel University, Vallabh Bidyanagar - 3881203Department of Physics, Panjab University, Chandigarh - 160014

4Inter University Accelerator Centre, New Delhi - 110 067

The study of heavy ion induced multi-nucleon trans-fer reactions can be used as an useful tool to investi-gate the underlying reaction mechanism and the inter-play of different reaction processes. The cross sectionfor multinucleon transfer around and above the Coulombbarrier is found to be enhanced in many cases in com-parison to what is expected for successive non-correlatedtransfer of nucleons [1]. In a semi-classical description,the cross section for transfer of N nucleons can be writ-ten as [2] (dσ/dΩ)tr=PN × (dσ/dΩ)el where (dσ/dΩ)tr

and (dσ/dΩ)el are the transfer and elastic scatteringcross sections, respectively. The probability of N-nucleontransfer, PN , would be equal to (P1)N in the case of un-correlated transfer. Deviation from this value would bea measure of clustering/correlation amongst nucleons.

In a recent study at the Inter Universuty AccelerattorCentre(IUAC), Delhi, cross section for transfer of upto 6nucleons (using silicon surface barrier detectors in simple∆E-E configuration) have been measured by us for thesystems 12C+58Ni and 12C+56Fe at ELab= 45 and 60MeV. For the four nucleon transfer channel (12C,8Begs),α-α coincidence measurement for detection of 8Be→ααbreakup events was performed. The α-α opening anglewas kept at ∼ 6o and the relative energy spectrum (Erel)between two α’s was used to identify 8Begs (Fig. 1). Fromthe kinetic energy spectrum of 8Be, the excited states incorresponding residual nuclei were identified.

FIG. 1: Spectrum of the relative energy between two α. Thepeak corresponds to the detection of two alpha particles com-ing from the decay of 8Begs.

TABLE I: Optical model potential parameters extracted usingthe search code SFRESCO.

Potential Parameter 12C+56Fe 12C+58Ni 12C+58Ni

@60 MeV @ 60 MeV @ 45 MeV

Vo (MeV) 48.0 48.0 48.0

ro (fm) 1.191 1.044 0.950

ao (fm) 0.643 0.634 0.910

W (MeV) 12.0 12.0 12.0

ri (fm) 1.191 1.136 1.255

ai (fm) 0.634 0.502 0.490

To gain insight into the role of multi-nucleon corre-lations in the transfer processes, probabilities for mult-inucleon transfer reactions, as defined above, have beenextracted. The elastic scattering angular distribution hasbeen measured simultaneously along with transfer chan-nels and have been analysed by the optical model searchprogramme SFRESCO. The best fit parameters are listedin Table I. In Table II we list the measured cross sectionsfor N-nucleon stripping and deduced transfer probabili-ties PN (preliminary results). Data are being analyzedto extract ’Enhancement Factor’ over the un-correlatedsequential transfer of nucleons and to understand the re-action mechanism aspects.

TABLE II: Data for E(12C) = 60 MeV and θlab= 30 deg.Columns 3 and 4 are the values for the system 12C+58Niwhile columns 5 and 6 are for 12C+56Fe.

Channel ∆N σtr(mb/sr) PN (%) σtr(mb/sr) PN (%)

(12C,11C) 1 1.95 0.140 0.65 0.210

(12C,11B) 1 1.00 0.070 1.16 0.380

(12C,10B) 2 0.45 0.030 0.39 0.130

(12C,10Be) 2 0.02 0.001 0.052 0.017

(12C,9Be) 3 0.24 0.017 0.25 0.083

(12C,7Be) 5 0.08 0.005 0.03 0.010

(12C,7Li) 5 0.10 0.007 0.05 0.017

(12C,6Li) 6 0.22 0.016 0.07 0.022

∗corresponding author: [email protected]

[1] B. J. Roy et al, Nucl. Phys. A588, 706 (1995). [2] W. von Oertzen et al, Nucl. Phys. A207, 91 (1973).

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FUSION14

Coupling with two-center neutron states and two-surface collective excitationsat fusion reactions in vicinity of Coulomb barrier

V. Samarin∗Joint Institute for Nuclear Research, Dubna, Moscow region, Russia

The vibration channel coupling effects in fusion reac-tions were studied using coupled channel equations withenergy and amplitude limitation [1]. The experimen-tal fusion cross section σ(Ec.m.) [2] has the fine struc-ture of the barrier distribution D(Ec.m.), Fig. 1a. Thisstructure is interpreted using energy levels εα(R) of two-surface quadrupole and octupole vibrations of closely lo-cated nuclei on distance R [1]. The most populatedtwo-surface vibration states in vicinity of the barrier arelabeled with A, B and C in Fig. 1b. These points arecorresponded to the A, B and C peaks of the calculatedbarrier distribution D(Ec.m.) in Fig. 1a. There is satis-factory agreement between experimental and calculatedbarrier distributions for reactions 40Ca + 90Zr, 36S +90Zr, 40Ca + 40Ca, 16O + 144Sm in the number of peaks,their relative heights and the shapes. The neutron chan-nel coupling effects in fusion reactions were studied us-ing time-dependent wave functions of external neutrons[3, 4]. These functions were interpreted as superposi-tion of two-center stationary wave functions calculatedby method using the Bessel functions [5]. The jumpfrom two-center energy level 2d5/2(Zr) to two-center level2p3/2(Ca) explains essential difference of fusion cross sec-tions between reactions 40Ca+96Zr and 40Ca+90Zr [2].

Similarly jump from two-center level 1d5/2(O) to two-center level 1g9/2(Ni) explains essential difference of fu-sion cross sections between reactions 18O + 58Ni and 18O+ 58Ni [6]. Both jumps have positive Q-values and rel-atively large probabilities.

a b

FIG. 1: a) Experimental (points) and calculated (curve) bar-rier distribution D(Ec.m.) for fusion cross section of reaction40Ca + 90Zr; b) Energies ε(R) of two-surface quadrupole andoctupole vibration levels in the 40Ca + 90Zr system, RB isthe radius of the Coulomb barrier top for spherical nuclei ofradii R1 and R2.

∗corresponding author: [email protected]

[1] V. V. Samarin, Phys. of Atom. Nucl, 74, 1682 (2009).[2] H. Timmers, et al., Nucl. Phys. A 633, 421, (1998).[3] V. V. Samarin, V. I. Zagrebaev, W. Greiner. Phys Rev. C

75, 035809 (2007).[4] V. V. Samarin, K. V. Samarin, Bull. Russ. Acad. Sci.

Phys. 74, 567 (2010).[5] V. V. Samarin, Phys. of Atom. Nucl. 73, 1416 (2010).[6] A. M. Borges, et al., Phys. Rev. C 46, 2360 (1992).

72

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FUSION14

Time-dependent quantum models of near barrier nucleon transfer reaction dynamics

V. Samarin∗Joint Institute for Nuclear Research, Dubna, Moscow region, Russia

Numerical solution of the time-dependent Schrodingerequation provides a new possibilities for theoretical studyof transfer reaction dynamics [1]. In this study the spin-orbital interaction and Pauli’s exclusion principle weretaken into consideration. Time-dependent Schrodingerequation is numerically solved by difference method [2]for external neutrons of spherical nuclei 6He, 48Ca anddeformed nucleus 238U at their grazing collisions with en-ergies in vicinity of the Coulomb barrier. The visual com-puter animations of probability density evolution (Fig. 1)are calculated. The probabilities of neutron transfer inreactions 6He + 197Au, 40,48Ca + 238U are determinedas function on minimum inter-nuclear distances. It isfound, that the nucleons transfers for small values of fullnucleon angular moment projection on an inter-nuclearaxis at closed approach of nuclei are most probable. Thecalculation results of cross section for formation of the198Au isotope in the 6He+197Au reaction agree satisfac-torily with the experimental data [3, 4] near the barrier.

FIG. 1: Change in the probability density of the externalneutrons of an 6He nucleus with the initial state 1p3/2 during

a collision with the 197Au nucleus at energy in the center ofmass system E = 19 MeV near the barrier. The course oftime corresponds to the panels locations from left to right.

∗corresponding author: [email protected]

[1] V. V. Samarin, V. I. Zagrebaev, W. Greiner. Phys Rev. C75, 035809 (2007).

[2] V. V. Samarin, K. V. Samarin, Bull. Russ. Acad. Sci.Phys. 74, 567 (2010).

[3] A. Kulko A. et al., J. Phys. G 34, 2297 (2007).[4] V. V. Samarin, K. V. Samarin, Bull. Russ. Acad. Sci.

Phys. 76, 450 (2012).

73

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FUSION14

Deformation and orientation effects in heavy-particle radioactivity of Z=115

Gudveen Sawhney,1, ∗ Kirandeep Sandhu,2 Manoj K. Sharma,2 and Raj K. Gupta1

1Department of Physics, Panjab University, Chandigarh -160014, India2School of Physics and Materials Science, Thapar university Patiala - 147004, India

The radioactive decay of nuclei emitting particle heav-ier than alpha-particle was first predicted by Sandulescuet al. [1] in 1980 on the basis of quantum mechanical frag-mentation theory. Later it was confirmed experimentallyby Rose and Jones in 1984 [2] via the 14C decay from223Ra nucleus. With this discovery, a big hunt for moreand more cluster emitters got stimulated and as a re-sult today we have a whole family of cluster radioactivityemitting numerous clusters ranging from 14C to 34Si. Allthe cluster emitters studied so far, belong to trans-leadregion, giving closed shell 208Pb or its neighboring nucleias residual or daughter nucleus. Recently, the domain ofcluster radioactivity has been further widened by Poe-naru et al. [3]. Knowing that the role of shell effects isthe central feature in the cluster decay process studiedso far, they explored the heavy-particle radioactivity ofsuperheavy nuclei in which unstable parent nuclei havingZ > 110 decays into a cluster with Zcluster > 28 with adoubly magic daughter around 208Pb.

Following this idea, we have studied the ground statedecay of 289115 using the Preformed Cluster Model(PCM) [4, 5], that has been observed [6] in the 2n-evaporation channel produced in a fusion reaction of48Ca beam with the 243Am target. Since the fragmenta-tion process depends on the collective clusterization ap-proach, therefore in PCM, not only the shapes of par-ent, daughter and cluster are important but also of allother possible fragments anticipated in the decay. In ad-dition to shell effects, it is expected that nuclear deforma-tions and orientations also play an important role in thecluster decay process. In order to look for such effects,Fig. 1 shows the fragmentation potential of the parentnucleus 289115 for the case of quadrupole deformationβ2 and “optimum” orientations [7] taken into accountfor all the possible fragments. Note that the orienta-tions are ‘optimized’ (uniquely fixed) on the basis of β2i

alone which manifests in the form of “hot (compact)” and“cold (non-compact)” configuration. The ‘hot compact’

configuration corresponds to smallest interaction radiusand highest barrier whereas the ‘cold non-compact’ con-figuration corresponds to largest interaction radius andlowest barrier. Using PCM, the decay characteristics of289115 nucleus clearly shows that 83As is most proba-ble heavy particle with 206Pb daughter for the choiceof optimum orientations of ‘compact hot’ configuration.In other words, region for heavy particle radioactivity is

FIG. 1: Fragmentation potential for the parent nucleus 289115taken all possible fragments with quadruple deformation β2

and “optimum” orientations.

more favorable (minimum potential energy) and henceshow a clear preference for ‘hot compact’ in comparisonto ‘cold non-compact’ configuration.

One may conclude that proper understanding of nu-clear shapes along with the relative orientations is essen-tial to make concrete and explicit predictions/ verifica-tions of the clusterization process in superheavy region.As an extension of this work, it will be interesting to seethe effect of higher multipole deformations in referenceto heavy-particle radioactivity.

∗corresponding author: [email protected]; Permanent ad-

dress:Physics Department, Panjab University, Chandigarh-160014

[1] A. Sandulescu, D. N. Poenaru, and W. Greiner, Sov. J.Part. Nucl. 11, 528 (1980).

[2] H. J. Rose and G. A. Jones, Nature (London) 307, 245(1984).

[3] D. N. Poenaru, R. A. Gherghescu, and W. Greiner, Phys.Rev. C 85, 034615 (2012).

[4] S. S. Malik and R. K. Gupta, Phys. Rev. C 39, 1992(1989).

[5] G. Sawhney, M. K. Sharma, and R. K. Gupta, Phys. Rev.C 83, 064610 (2011).

[6] Yu.Oganessian et al., Phys. Rev. C 87, 014302 (2013).[7] R. K. Gupta, M. Balasubramaniam, R. Kumar, N. Singh,

M. Manhas, and W. Greiner, J. Phys. G: Nucl. Part. Phys.31, 631 (2005).

74

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FUSION14

Effect of pairing on transfer and fusion reactions

Guillaume Scamps1, ∗ and Denis Lacroix2, †1GANIL, CEA/DSM and CNRS/IN2P3, Boıte Postale 55027, 14076 Caen Cedex, France

2Institut de Physique Nucleaire, IN2P3-CNRS, Universite Paris-Sud, F-91406 Orsay Cedex, France

Pairing correlations play a major role in nuclear struc-ture. In the present contribution, the effect of pairingon nuclear reactions like particle emission, transfer andfusion is discussed. The Time-Dependent Hartree-FockBogolyubov (TDHFB) theory has been developed to in-corporate pairing theory in a microscopic transport the-ory using a TDHF+BCS simplified version. Applicationof pairing theories to schematic one dimensional modelhas pointed out the advantages and drawbacks of theseapproaches [1].

Recently, a TDHF+BCS code in 3D using realisticskyrme interaction has been developed. This theory, ap-plied to giant resonances, is showed to be easily imple-mented and rather efficient to describe collective motionof superfluid system [2]. Conjointely, this approach wasused to study the effect of the pairing correlations ontransfer reactions. It was demonstrated that one and twoparticle transfer are considerably affected by initial pair-ing correlations in one of the collision partners [3]. Somereactions of recent and future interest will be discussed.

∗Electronic address: [email protected]†Electronic address: [email protected]

[1] G. Scamps, D. Lacroix, G. F. Bertsch, K. Washiyama,Phys. Rev. C 85, 034328 (2012).

[2] G. Scamps, D. Lacroix, Phys. Rev. C 87, 014605 (2013).

[3] G. Scamps, D. Lacroix, Phys. Rev. C 88, 044310 (2013).

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FUSION14

Time-dependent Hartree-Fock calculation for multinucleon transfer processes

Kazuyuki Sekizawa1, ∗ and Kazuhiro Yabana1, 2

1Graduate School of Pure and Applied Sciences, University of Tsukuba2Center for Computational Sciences, University of Tsukuba

In low-energy nuclear reactions around the Coulombbarrier, multi-nucleon transfer (MNT) reactions are com-monly observed at an impact parameter region slightlyoutside that corresponding to fusion reactions. The MNTreaction has been attracting much interests in a numberof aspects. While microscopic mechanisms of the processattract theoretical interests as non-equilibrium quantumtransport phenomena, it has been expected to be a newmeans to produce unstable nuclei whose production isdifficult by other methods.

We have been studying MNT reactions employing thetime-dependent Hartree-Fock (TDHF) theory, a fully mi-croscopic quantum many-body simulation. To the au-thors’ knowledge, it is the first serious attempt to applythe TDHF theory to the MNT reaction.

As a first step, we have studied MNT reactions in sev-eral systems for which extensive measurements are avail-able [1]. As a representative example, we show results ofthe TDHF calculation for 58Ni+208Pb reaction at Elab =328.4 MeV. In Fig. 1, we show results of the TDHF cal-culation for the average number of transferred nucleonsas functions of the impact parameter, b. From the figure,we find that there are two kinds of transfer mechanismsdepending on the impact parameter. At a large impactparameter region (3 fm ≲ b), neutrons and protons aretransferred towards opposite directions, directing to thecharge equilibrium. At a small impact parameter region

-2

0

2

4

6

8

10

0 1 2 3 4 5 6 7 8

∆N

b (fm)

58Ni+

208Pb (Elab=328.4 MeV)

Neutron

Proton

FIG. 1: Average number of transferred nucleons from thetarget (208Pb) to the projectile (58Ni) as a function of theimpact parameter, b.

(b ≲ 3 fm), a neck breaking dynamics is responsible forthe transfer. A number of nucleons in the neck region aretransferred when the neck is broken, leading to transfersof both protons and neutrons in the same direction.

To calculate the cross sections, we apply a particlenumber projection method which was recently proposedby C. Simenel [2]. We further calculate excitation ener-gies of final fragments extending the projection theory.

In Fig. 2, we show cross sections classified accordingto the change of the proton number of the projectile-like fragment (PLF) from 58Ni, as functions of neutronnumber of the PLF. Red filled circles denote measuredcross sections [3] and red solid (blue dotted) lines denoteresults of the TDHF calculations without (with) effectsof particle evaporation. As the figure shows, the TDHFtheory describes surprisingly well the measured cross sec-tions when the number of transferred nucleons is small.We note that there is no empirical parameter in our cal-culations, since we employ a standard Skyrme effectiveinteraction (SLy5). As the number of transferred nucle-ons increases, there appear discrepancies even when weinclude evaporation effects. This fact may indicate signif-icance of correlation effects beyond the time-dependentmean-field theory.

σ tr

(mb

)

(+1p)

10-4

10-3

10-2

10-1

100

101

102

103

28 32 36 40 44

58Ni+

208Pb (Elab=328.4 MeV)

(0p)

28 32 36 40 44

(-1p)

28 32 36 40 44

(-2p)

Exp.TDHF w/o evap.TDHF w evap.

28 32 36 40 44

σ tr

(mb

)

(-3p)

10-4

10-3

10-2

10-1

100

101

102

103

28 32 36 40 44

(-4p)

28 32 36 40 44

NEUTRON NUMBER of PLF

(-5p)

28 32 36 40 44

(-6p)

28 32 36 40 44

FIG. 2: Lines show TDHF calculations with and withoutevaporation effects for production cross sections of the pro-jectile (58Ni) like fragments in 58Ni+208Pb reaction at Elab =328.4 MeV. Measured data are also shown by filled circles.

∗corresponding author: [email protected]; Presentaddress: 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan

[1] K. Sekizawa and K. Yabana, Phys. Rev. C 88, 014614(2013).

[2] C. Simenel, Phys. Rev. Lett. 105, 192701 (2010).[3] L. Corradi et al., Phys. Rev. C 66, 024606 (2002).

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FUSION14

Fusion excitation function measurement for 6Li+64Ni at near the barrier energies

Md. Moin Shaikh,1, ∗ Subinit Roy,1 S. Rajbanshi,1 M. K. Pradhan,1 A Mukherjee,1

P. Basu,1 S. Pal,2 V. Nanal,2 R. Pillay,2 R. Palit,2 and A. Shrivastava3

1Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata-700 064, India2Tata Institute of Fundamental Research, Mumbai-400 005, India

3Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085, India

Reactions with weakly bound stable projectiles havebeen studied on several targets [1–4] in order to investi-gate the role of breakup channel on scattering and fusionin different mass region. Breakup is said to suppress thecross section of complete fusion (CF) of the projectile atenergies above the barrier compared to the model predic-tions including the coupled channel calculation. The sup-pression of complete fusion (CF) is accounted for with theprocess of incomplete fusion (ICF) of a part of the weaklybound projectile with the target. In general, the suppres-sion is expected to decrease with decreasing charge of thetarget [5–7]. But in a recent work Kumawat et al. [8]demonstrated the existence of a uniform suppression ofabout 30% of complete fusion cross section independentof charge of the target for 6Li projectile. The effect wasattributed to the dominance of nuclear induced breakupover Coulomb breakup for 6Li. However, an exception ofthe trend was observed for 6Li+59Co system. In this

FIG. 1: Representative characteristic γ-spectrum from6Li+64Ni fusion at 26 MeV .

context, we intend to present our recent measurementof fusion excitation function for 6Li+64Ni system usingthe characteristic γ-ray detection technique. The exper-iment was carried out at the TIFR/BARC Pelletron Fa-cility in Mumbai with ∼99% enriched 64Ni target. The

FIG. 2: Excitation function for different reaction channels of6Li+64Ni.excitation function was measured over the incident en-ergy of 11 to 28 MeV with the barrier for the system be-ing ∼13.8 MeV in laboratory. A thin Be-window n-typeand an Al-window p-type HPGe dtdectors were used atforward(45) and backward (125) angles. Dominant 2n,3n and pn evaporation channels coming from purely com-plete fusion process were identified along with other chan-nels from ICF and transfer processes. A representativespectrum is shown in Fig. 1. Experimental fusion, trans-fer and inelastic excitation functions have been shown inFig. 2. The fusion data in Fig. 2 includes the contribu-tion from both CF and ICF channels. Comparison with1-DBPM prediction indicates an enhancement of fusionat sub-barrier energies. Extraction of complete fusioncross section for 6Li+64Ni system and subsequent obser-vation of suppress, if any, will be presented.∗[email protected]; Nuclear Physics Division, Saha Institute

of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700 064, India

[1] M. Dasgupta et al., Phys. Rev. C 70, 024606 (2004).[2] C. Beck et al., Phys. Rev. C 67, 054602 (2003).[3] A. Mukherjee et al., Phys. Lett. B 636, 91 (2006).[4] P.R.S. Gomes et al., Phys. Rev. C 71, 034608 (2005).[5] P.K. Rath, et al., Phys. Rev. C 79, 051601(R) (2009).

[6] D.J. Hinde, et al., Phys. Rev. Lett. 89, 272701 (2002).[7] P.R.S. Gomes, et al., Phys. Rev. C 84, 014615 (2011).[8] H. Kumawat, et al., Phys. Rev. C 86, 024607 (2012).

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FUSION14

Fission dynamics of 240Cf∗ formed in 34,36S induced reaction

D. Jain,1 G. Kaur,1 and M. K. Sharma1, ∗

1School of Physics and Materials Science, Thapar University, Patiala-147004, India.

In low energy heavy-ion collisions, fusion-fission andrelated nuclear phenomena have always been of centralinterest. Depending upon the incident energy of the pro-jectile as well as angular momentum, the collision of in-teracting nuclei may lead to several interesting phenom-ena such as quasifission (qf), particle production, incom-plete fusion (ICF) etc., in addition to the usual completefusion (CF) process. The formation of heavy and super-heavy elements is considered by CF, involving the totalamalgamation of the colliding nuclei forming an equilib-erated compound nucleus (CN). However, due to strongrepulsive Coulomb force the composite system formedby the projectile and target nuclei may reseparate be-fore complete fusion leading to the so-called qf process.Many factors, such as deformation and orientation of thecolliding nuclei, their mass asymmetry and the closed-shell nature, can potentially affect the qf process. Thusthe choice of a suitable projectile-target combination aswell as optimum beam energy are crucial for a successfulsynthesis of the heavy nuclei.

Recently, an experiment was performed to measure fis-sion cross section of 240Cf∗ produced in irradiation of204,206Pb target with 36,34S ions respectively at energiesabove as well as below the Coulomb barrier [1]. It is ofinterest to study 240Cf∗ system as it is formed via twodifferent incoming channels and belongs to actinide re-gion whose experimental data on decay properties arerare due to low production rate. Here, we study the de-cay of compound nucleus 240Cf∗ by using the dynamicalcluster decay model (DCM) [2] via the nuclear proximitypotential derived from Skyrme energy density formalism(SEDF) [3] having an advantage of using different Skyrmeforces with different barrier characteristics. It is worthmentioning that DCM treats all the decay processes (ER,fission and qf) on equal footing as barrier penetration ofpreformed fragments. In this paper, we have used wellestablished SIII force to study entrance channel effectthrough preformation probability curve and tried to fitthe fission cross section with in the framework of DCM.

Firstly, Fig. 1(a) shows the calculated preformationprobability for the decay of 240Cf∗ compound systemformed using two different entrance channels (36S+204Pband 34S+206Pb) with the use of SIII force at the extremevalues of angular momentum i.e. at `=0 and `max. In

order to do a comparison between the two incoming chan-nels, the same center-of-mass energy Ec.m.' 138 MeV ischosen. It is clear from Fig. 1(a) that the decay pat-tern overlap each other at `=0 and `max, keeping other

FIG. 1: (a) Preformation probability as a function of fragmentmass Ai for the decay of 240Cf∗ formed in 36S+204Pb and34S+206Pb reaction channels, (b) Comparison of experimentaland DCM based fission cross sections calculated using SIIIforce for 240Cf∗ nucleus formed in 36S+204Pb reaction.

variables approximately same for both the channels. Itmeans the preformation probability suggest no signatureof entrance channel effect in the dynamics of 240Cf∗ nu-cleus. We note that the contribution of fragments form-ing the secondary peaks (shoulder) is very small (i.e.main contribution is due to the symmetric fragments).One may also notice that at `=0, the light fragments (rep-resenting ER) are more dominant with negligible contri-bution of fission component which otherwise start com-peting with the ER at higher `-values. Also, the σfiss

are calculated for 36S+204Pb reaction, in reference to ex-perimental data, with in the framework of DCM for SIIIforce as shown in Fig. 1(b). the calculations have beendone by fitting the only parameter of the model, the necklength parameter ∆R, which varies as a function of cen-ter of mass (c.m.) energy. We find that for each c.m.energy, the fits obtained are in good agreement with theexperimental data, except at higher two energies wherethe qf process seems to compete with the fission, andthe sum of these two, i.e., σfiss + σqf , fits the availabledata nicely. It will be of further interest to study the fis-sion cross section of 34S+206Pb→240Cf∗ by using DCMin order to check the consistency of qf component.

[email protected]

[1] J. Khuyagbaatar et al., Phys. Rev. C 86, 064602 (2012).[2] R. K. Gupta, Lecture Notes in Physics 818, Clusters in

Nuclei, ed C. Beck, Vol. I, (Springer Verlag, 2010) p 223.

[3] J. Bartel and K. Bencheikh, Eur. Phys.J.A 14, 179 (2002).

78

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FUSION14

Statistical model calculation for evaporation residue and fission cross section for48Ti+122Sn system

Priya Sharma,1, ∗ B. R. Behera,1 Santanu Pal,2 and N. Madhavan3

1Department of Physics, Panjab University, Chandigarh 160014, India2CS-6/1 Golf Green, Kolkata 700095, India (Formerly with VECC, Kolkata)

3Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India

Statistical model calculations have been performed tounderstand the HYRA [1] spectrometer for 48Ti like in-duced reactions. For this, we have planned to mea-sure the ER and fission cross section for 48Ti + 150,142

Nd,144Sm systems. In the present work, theoretical cal-culations and fission cross section have been performedfor 48Ti+122Sn system, by fitting the available experi-mental data from literature [2] by using the statisticalmodel code [3].

100

1000

σ(m

b)

ER

130 135 140 145 150 155 160E

c. m.(MeV)

1

10

100

1000

σ(m

b)

Fission

Kf=0.5

Kf=0.6

Kf=0.7

Kf=0.8

Kf=0.9

Kf=0.95

Kf=1.0

FIG. 1: Dots are the experimental data and different linesare the theoretical calculations for different scaling factor, Kf

(as given inside the diagram): (a) For ER cross section (b)Fission cross section.

One of the important input of the statistical modelis the spin distribution of the fused system which canbe obtained by fitting the experimental fusion cross sec-tion with a suitable model. So, to reproduce the ex-perimental fusion cross section, couple channel calcula-tions have been performed using the code CCFULL [4].Here, the projectile 48Ti is having permanent quadrupoledeformation. The coupling of first 2+ states of target(Eex=1.140 MeV, β2=0.103) and projectile (Eex=0.983,

β2=0.27) has been considered as vibrational excitations.The potential parameters were found to be V0=130 MeV,r0=1.16 fm and a0=0.61 fm. Spin distribution obtainedfrom CCFULL output has been used as an input for thespin distribution of compound nucleus in the statisti-cal model code. Then final theoretical calculations wereperformed using Bohr-Wheeler formalism including shellcorrection in the level density. To reproduce experimen-tal ER and Fission cross sections, the liquid drop fissionbarrier (Bf ) need to be scaled in the statistical model cal-culation. For this, the scaling factor (Kf ), which givesthe ratio of experimental to calculated fission barrier hasbeen varied from 0.5 to 1.0. as shown in Fig. 1.

130 135 140 145 150 155 160E

c. m.(MeV)

0.5

0.6

0.7

0.8

0.9

1

Kf

ERFission

VB

FIG. 2: Best-fit values of Kf as a function of Ec.m. for48Ti+122Sn.

From the calculations it is found that, for ER and fis-sion cross section lower energies lower energies Kf variesin the range 0.5-0.8 but for higher energies Kf its rangeis 0.9-1.0 as shown in Fig. 2. The lower values of Kf atlower energies may indicate quasi-fission(QF) which re-duces the fusion cross section. In Fig. 2, we are getting adeviation of Kf from the general trend (for both ER andFission) at some energy points and it essentially reflectsthe lower experimental fission cross section and higherER cross section at those particular energy. It is somewhat surprising. More measurement in this mass regionis necessary to understand the fission and ER cometition.∗corresponding author: [email protected]

[1] N. Madhavan et al., Pramana J. Phys. 75, 317 (2010).[2] S. Gil et al. , Phys. Rev. C 51, 13361344 (1995).[3] J. Sadhukhan and S. Pal, Phys. Rev. C 81, 031602 (R)

(2010).

[4] K. Hagino, N. Rowley, A. T. Kruppa, Comput. Phys.Commun. 123, 143 (1999).

79

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FUSION14

Incomplete fusion reactions in 16O+159Tb system: Spin distribution measurements

Vijay R. Sharma,1, ∗ Abhishek Yadav,1, † Devendra P. Singh,1 Pushpendra P. Singh,2 Sunita Gupta,3 Manoj K.Sharma,4 R. Kumar,5 S. Muralithar,5 R. P. Singh,5 R. K. Bhowmik,5 B. P. Singh,1 and R. Prasad1

1Physics Department, Aligarh Muslim University, Aligarh 202 001, India2GSI Helmholtz, Centre for Heavy Ion Research GmbH, Darmstadt - 64291, Germany

3Physics Department, Agra College, Agra- 282 001, India4Physics Department, S. V. College, Aligarh - 202 001, India

5Nuclear Physics Group, Inter University Accelerator Centre, New Delhi - 110 067, India

From the recent reports on low energy nuclear reac-tion dynamics, it may be inferred that incomplete fu-sion (ICF) processes may be used as spectroscopic toolto study the high spin states [1–4]. The ICF processes areconsidered to result from the peripheral collisions asso-ciated with large input angular momentum in heavy ion(HI) induced reactions, where excess angular momentado not allow the complete fusion (CF) to occur. Aimingto probe the incomplete fusion reaction dynamics and thedriving input angular momenta involved in CF and ICFreactions, a particle-γ-coincidence experiment has beenperformed at the Inter-University Accelerator (IUAC),New Delhi using Gamma Detector Array (GDA) along-with charged particle detector array (CPDA) setup, for16O+159Tb system at energy ≈ 4-7 MeV/nucleon. Coin-cidences were recorded between prompt γ-rays detectedby HPGe detectors and charged particles (Z=1,2) de-tected by the Phoswich detectors.

To look for the driving input angular momenta as-sociated in various channels populated via CF and/orICF, spin-distributions of several reaction products havebeen measured. In these measurements, different reac-tion modes have been disentangled on the basis of entrystate spin population during the de-excitation of com-pound nucleus produced via CF and/or ICF processes. Itmay further be pointed out that, an excited/equilibratedcompound nucleus produced through CF and/or ICFprocesses, generally, leads to the final reaction product(s)via emission of characteristic γ-rays and/or light nuclearparticle(s). In such a case, two type of decay steps maytake place, viz; (i) those that de-excite the compoundnucleus to or towards the yrast line, and are expected toremove less angular momentum and more excitation en-

ergy called statistical transitions, and (ii) those that areroughly parallel to the yrast line, and remove more an-gular momentum and relatively less excitation energy incomparison to statistical transitions. In order to have aninsight into input angular mometa, the spin-distributionsof residues populated via xn channels i.e., 171Ta (4n) and170Ta (5n) have been determined from the singles spectra.The p4n channel residues, 170Hf populated via CF route,have been identified using the backward proton-gated γspectra i.e., backward α-gated γ spectra subtracted frombackward particles (Z = 1, 2)-gated γ spectra. For theidentification of pure CF α channels, the backward α-gated γ spectra have been used, whereas, for the breakupα particles or fast α-components, the forward α-gated γspectra are used. In order to remove any contaminationfrom the slow α component in the forward cone, back-ward α-gated γ spectra are subtracted from the forwardα-gated γ spectra. In the present work, 168Lu (α3n) and167Lu (α4n) populated via CF and ICF route have beenidentified. The spin distributions of ICF-αxn channelsare found to be distinctly different from those observedfor CF-xn/pxn/αxn channels, and indicates entirely dif-ferent de-excitation patterns for the CF and ICF prod-ucts. It has been observed that the complete fusion prod-ucts are strongly fed over a broad spin range, however, in-complete fusion products are found to be less fed and/orthe population of lower spin states are strongly hindered.Further, the analysis of data indicates that the mean in-put angular momenta for CF residues are significantlyless as compared to for the ICF residues populated viadirect α-emitting channels. Details of the analysis along-with the observations and results will be presented.

∗corresponding author: [email protected]†corresponding author: [email protected]

[1] G. D. Dracoulis et al., J. Phys. G: Nucl. Part. Phys. 23,1191 (1997).

[2] Pushpendra P. Singh, et al., Phys. Lett. B 671, 20-24(2009), references therein.

[3] Pushpendra P. Singh, et al., Phys. Rev. C 78, 017602(2008), references therein

[4] G. J. Lane et al., Phys. Rev. C 60, 067301 (1991) andreferences therein.

80

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FUSION14

Incomplete fusion systematics with Universal Fusion Function model and α-Q value

Vijay R. Sharma,1, ∗ Abhishek Yadav,1 Devendra P. Singh,1 Pushpendra P. Singh,2 Sunita Gupta,3

Manoj K. Sharma,4 Indu Bala,5 R. Kumar,5 S. Muralithar,5 B. P. Singh,1 and R. Prasad1

1Physics Department, Aligarh Muslim University, Aligarh 202 001, India2GSI Helmholtz, Centre for Heavy Ion Research GmbH, Darmstadt - 64291, Germany

3Physics Department, Agra College, Agra- 282 001, India4Physics Department, S. V. College, Aligarh - 202 001, India

5Nuclear Physics Group, Inter University Accelerator Centre, New Delhi - 110 067, India

The study of heavy ion reactions is important not onlyin its own right, but is significant also for its impact onthe study of break up effects in fusion reactions. Investi-gation of nuclear reactions with strongly as well as weaklybound projectiles have an important implications in thefield of nuclear astrophysics as well. Some of these reac-tions may be important doorways to the production ofradioactive ion beams. Experimentally, the breakup ofprojectiles from massive transfer reactions was first ob-served by Britt and Quinton [1]. These reactions werelater termed as incomplete fusion (ICF) processes. Re-cent studies [2, 3] on ICF using statistical model codesshowed the total reaction cross-section is relatively higherthan the complete fusion cross-section. On the other, thesuppression of complete fusion cross-section [4, 5] as com-pared to one dimensional barrier penetration model [6]has been observed.

Recently, Diaz-Torres [7] et al., proposed a three di-mensional classical model for low energy breakup fusionstudies, which is found to be valid only for the weaklybound projectiles and allows a consistent calculation ofbreakup, incomplete and complete fusion cross sections.For strongly bound projectiles the available models ex-plain the data to some extent at higher energies i.e. ≈8 MeV/nucleon. Hence, at energies near and around thecoulomb barrier, no such model is present which can ex-plain the ICF phenomenon satisfactorily.

In view of the above, it is important to understandthe mechanism of breakup and its effect on the fusionprocess. As such, in the present work, an attempt hasbeen made to explore and to study systematic behavior ofICF processes. Several strongly as well as weakly bound

projectiles (i.e., 12,13C, 16O on 159Tb, 169Tm and 181Ta)with different mass asymmetry and uncoupled parame-ters are chosen, which are further renormalized within theframework of recently proposed Universal Fusion Func-tion (UFF) [8] approach. It may be relevant to men-tion that the experimental fusion cross-section data hasbeen taken from our recent experiments [2, 3, 9, 10] per-formed at the IUAC, New Delhi, India. Detailed dis-cussion on experimental methodologies, obtained resultsand their interpretations may be found elsewhere [11].In the UFF model the complete fusion reaction function;Fexpt = 2EσCF /(~ωRB2) has been plotted against thequantity x = (E - Vb)/~ω, where ~ω is the barrier cur-vature. However, to eliminate the coupling effects, thecomplete fusion reaction function is normalized as Fexpt

→ fexpt = Fexpt(σWF / σCC

F ), where σWF is the fusion cross

section calculated by the Wong’s approximation [6] andσCC

F is the cross section obtained with coupled-channelcalculations code CCFULL [12]. fexpt is then comparedwith UFF i.e. F0(x)=`n [1 + exp(2πx)]. In order togive strength for our findings with UFF model, severalother available systems for the projectiles 6,7Li, 10,11Band 19F on 159Tb target are also included. A compari-son of reduced experimental fusion function for both thestrongly as well as weakly bound projectiles for severalsystems indicates that as the α separation energy of theprojectile increases, the fusion suppression is reduced by≈ 15% - 20%. It may be pointed out that an empiricalWood-Saxon potential has been used in the calculationsafter the inclusion of modified parameters i.e., radius andsurface energy coefficients through out the calculations.Full details for the present analysis will be presented.∗corresponding author: [email protected]

[1] H. C. Britt and A. R. Quinton, Phys. Rev. 124, 877(1961).

[2] Vijay R. Sharma et al., Phys. Rev. C submitted (2013).[3] Abhishek Yadav et al., Phys. Rev. C 85, 034614 (2012).[4] D. J. Hinde, M. Dasgupta et al., Phys. Rev. Lett. 89,

272701 (2002).[5] A. Mukherjee et al., Phys. Lett. B 636, 91 (2006) and

references therein.[6] C. Y. Wong et al., Phys. Rev. Lett. 31, 766 (1973).[7] A. Diaz-Torres and I. J. Thompson, Phys. Rev. C 65,

024606 (2002).[8] P.R.S. Gomes et al., Phy. Rev C 71, 017601 (2005).[9] Pushpendra P. Singh, et al., Phys. Rev. C 80, 064603

(2009).[10] K. Sudarsan Babu et al., J. Phys. G 29, 1011 (2003).[11] Vijay R. Sharma et al., AIP Conf. Proc. 1524, 201 (2013)

and references therein.[12] K. Hagino et al., Comput. Phys. Commun. 123, 143

(1999).

81

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FUSION14

Emergence of fusion hindrance for asymmetric system at extreme sub barrier energies

A. Shrivastava,1, ∗ K. Mahata,1 S.K. Pandit,1 V. Nanal,2 K. Hagino,3 T. Ichikawa,4 C.S. Palshetkar,1

V.V. Parkar,1 K. Ramachandran,1 P.C. Rout,1 Abhinav Kumar,1 A. Chatterjee,1 and S. Kailas11Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India

2DNAP, Tata Institute of Fundamental Research, Mumbai 400005, India3Department of Physics, Tohuku University, Sendai 980-8578, Japan

4Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan

Recent measurements with medium-heavy nuclei ac-centuated phenomenon of fusion hindrance, observed asa steep change of slope in fusion excitation function andits logarithmic derivative (L(E)) with respect to the cou-pled channels (CC) calculation at deep sub-barrier ener-gies [1]. At present there are two successful models to ex-plain the deep sub-barrier fusion data - model suggestedby Misicu and Esbensen [2] based on sudden approxima-tion using M3Y potential with repulsive core and a dy-namical two-step model proposed by Ichikawa et al. [3]based on an adiabatic picture. Currently experimentalstudies at these low energies have been restricted mainlyto the measurement of fusion cross sections of symmetricsystems with the exception of 16O + 204,208Pb [4] and6Li+198Pt [5]. Unlike the sharp change in slope of L(E)as observed in symmetric medium-heavy systems, a sat-uration in the slope of L(E) was observed for asymmetric16O + 204,208Pb system [4] at the deep sub-barrier en-ergies. In case of very asymmetric system involving lightweakly bound projectile 6Li+198Pt [5] absence of fusionhindrance was reported, suggesting significance of adia-baticity in collision at energies well below the barrier.These observations show importance of accurate mea-surements of fusion cross section at energies deep belowthe barrier with different entrance channels to test andmodify present theoretical models while understandingthe phenomenon of fusion hindrance. With this moti-vation we performed measurement on asymmetric sys-tem 12C+198Pt, extending the earlier measurements [6]to energies deep below the barrier. Measurement of theexcitation function of residues resulting from fusion wereperformed using a recently developed sensitive and selec-tive off-beam method using KX and γ-ray coincidence [5].Beams of 12C from Pelletron Linac Facility-Mumbai werebombarded on a 198Pt target in the range of 46 to 63MeV. Plotted in Fig. 1 is fusion excitation function alongwith the data from Ref. [6]. L(E) obtained using twopoint and three point numerical derivative of fusion data

is shown in the inset and compared with that calculatedfor a constant astrophysical S-factor (Lcs) [1].

The data were analysed using the standard coupled-channels (CC) calculations and its extension that simu-lates a smooth transition between the two-body and theadiabatic one-body states by damping gradually the off-

45 50 55 60 65 70E

cm(MeV)

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

σ fus(m

b)

no couplingcoupled channeladiabatic model

45 50 55 60 65 70E

cm(MeV)

0

0.5

1

1.5

2

2.5

3

3.5

L(E

) (M

eV-1

)

2 point3 pointLcs

12C +

198Pt

Vb

FIG. 1: Fusion excitation function and L(E) for 12C + 198Pt.CC calculations with and without inclusion of coupling alongwith adiabatic model calculations are shown.

diagonal part of the coupling potential [7]. The standardCC calculations used Yukawa-plus-exponential potentialincluding the quadrupole excitation in 198Pt and 12C cou-pled in the vibrational mode. A change in slope in fusionexcitation function and L(E) as compared to CC calcula-tions is clearly observed at lowest energies indicating on-set of fusion hindrance. On inclusion of damping in theadiabatic framework an excellent agreement with the fu-sion and L(E) data was observed. These results and theirrelevance with respect to observations from 6,7Li+198Ptand systems with different mass asymmetry at deep sub-barrier energies will be presented.∗corresponding author:[email protected]

[1] C.L. Jiang et al., Phys. Rev. Lett. 89, 052701 (2002), C.L.Jiang, K.E. Rehm, B.B. Back and R.V.F. Janssens, Phys.Rev. C 79, 044601 (2009) and references therein.

[2] S. Misicu and H. Esbensen, Phys. Rev. Lett. 96, 112701(2006); ibid. Phys. Rev. C 75, 034606 (2007).

[3] T. Ichikawa, K. Hagino and A. Iwamoto, Phys. Rev. C 75,

064612 (2007).[4] M. Dasgupta et al., Phys. Rev. Lett. 99, 192701 (2007).[5] A. Shrivastava et al., Phys. Rev. Lett. 103, 232702 (2009).[6] A. Shrivastava et al., Phys. Rev. C 63, 054602 (2001).[7] T. Ichikawa, K. Hagino and A. Iwamoto, Phys. Rev. Lett.

103, 202701 (2009).

82

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FUSION14

Microscopic study of the effect of collective vibrations on low-energy fusion

C. Simenel,1, ∗ M. Dasgupta,1 D. J. Hinde,1 and E. Williams1

1Department of Nuclear Physics, RSPE, Australian National University, Canberra, ACT 0200, Australia

Near-barrier fusion can be strongly affected by the cou-pling between relative motion and internal degrees offreedom of the collision partners [1]. The time-dependentHartree-Fock (TDHF) theory and the coupled-channels(CC) method are standard approaches to investigatethis aspect of fusion dynamics [2, 3]. Both approachesare very different in nature: the TDHF formulation ispurely microscopic while the CC description is based ona macroscopic picture.

Despite their successes in describing low-energy fusion,both approaches present limitations:

• The TDHF approach does not incorporate tun-nelling of the many-body wave function and, thus,can describe fusion only above the barrier.

• CC calculations need external parameters to de-scribe the nucleus-nucleus potential and the cou-plings to internal degrees of freedom.

0 5 10 15 20E (MeV)

Oct

upol

e st

reng

th

40Ca

56Ni3

-

1

3-

1

FIG. 1: Octupole strength distribution calculated fromTDHF response to an octupole excitation in the linear regime.

Using, in one hand, the ability of TDHF to describe prop-erties of vibrational states (see, e.g., Ref. [4] for a recentapplication to giant resonance decay) as well as their cou-plings to relative motion [5], and, in the other hand, theability of CC calculations to treat tunnelling, we recentlyproposed a new method combining both approaches to

overcome these limitations [6]. CC calculations are per-formed using two types of inputs from Hartree-Fock (HF)theory: the nucleus-nucleus potential calculated with thefrozen HF method, and the properties of low-lying vibra-tional states and giant resonances computed from theTDHF linear response.

The effect of the couplings to vibrational modes is stud-ied with this technique in several systems. For example,Fig. 1 shows the octupole spectra in 40Ca and 56Ni. The3−1 state is at a much lower energy in 40Ca and is thenexpected to have a stronger effect on the fusion barrierdistribution [3]. This is confirmed by TDHF calculationsof the 40Ca+40Ca system in which the fragments exhibita strong octupole deformation when overcoming the fu-sion barrier as compared to the 56Ni+56Ni system (seeFig. 2).

FIG. 2: Isodentities calculated from TDHF at the barrier.

In addition to generating structures in the fusion bar-rier distributions, this work demonstrates that the cou-plings to both low-lying and high-lying vibrations alsoaffect the centroid of the barrier distribution, in goodagreement with the fusion thresholds predicted by stan-dard TDHF calculations [6]. As the only phenomenolog-ical inputs are the parameters of the Skyrme functionalused in the HF and TDHF calculations, the method pre-sented in this work has a broad range of possible applica-tions, including studies of alternative couplings, such ascouplings to rotational states [7] and to transfer channels[8, 9], or reactions involving exotic nuclei.∗corresponding author: [email protected]

[1] M. Dasgupta, D. J. Hinde, N. Rowley, and A. M. Stefnini,Annu. Rev. Nucl. Part. Phys. 48, 401 (1998).

[2] C. Simenel, Eur. Phys. J. A 48, 152 (2012) - review article.[3] K. Hagino and N. Takigawa, Prog. Theo. Phys. 128, 1061

(2012).[4] B. Avez and C. Simenel, Eur. Phys. J. A 49, 76 (2013).[5] C. Simenel, R. Keser, A. S. Umar, and V. E. Oberacker,

Phys. Rev. C 88, 024617 (2013).

[6] C. Simenel, M. Dasgupta, D. J. Hinde, E. Williams,arXiv:1310.6500 (submitted).

[7] C. Simenel, Ph. Chomaz, and G. de France, Phys. Rev.Lett. 93, 102701 (2004).

[8] C. Simenel, Phys. Rev. Lett. 105, 192701 (2010).[9] C. Simenel, Phys. Rev. Lett. 106, 112502 (2011).

83

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FUSION14

Heavy ion collision dynamics of 10,11B+10,11B reactions

BirBikram Singh,1, ∗ Manpreet Kaur,1 and Raj K.Gupta2

1Department of Physics, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140406, INDIA.2Department of Physics, Panjab University, Chandigarh-160014,INDIA.

Light heavy-ion reactions present novel and interest-ing features to understand the dynamics of light nuclearsystem A∼40-60, formed with various target+projectilecombinations, over a wide range of low bombardingenergies Elab≤10 MeV/nucleon.The viability of fusion-fission(FF)process and related reaction dynamics for suchlight compound nuclei has been a kind of established[1].Very light nuclear systems A ∼ 30 are also being stud-ied further to establish reaction dynamics involved [1].In the present work, the extreme case of decay of verylight nuclear systems 20,21,22Ne∗ formed in 10,11B+10,11Breactions [2] is being studied using Dynamical Clusterdecay Model(DCM) of Gupta and collbrators [1].TheDCM has been applied successfully to the decay ofvery light(A∼30), light, medium, heavy, super-heavymass compound nuclei for their decay to light parti-cles(evaporation residues), FF, quasi-fission (QF) de-pending on the reaction conditions.We intend to extendthe application of DCM to study the extreme case of de-cay of very light nuclear systems 20,21,22Ne∗, for whichexperimental data is available [2].It will be highly exciting to study the decay of sucha lighter systems for competing reaction mechanismsinvolved (specially orbiting phenomenon) as well asthe role of nuclear structure characteristics in colli-sion dynamics.Very preliminary study of these reactions10,11B+10,11B→20,21,22Ne∗→A1+A2, at Elab=48 MeV,based on DCM calculations, reveals the binary sym-metric decay of the complex systems formed except21Ne(Fig.1).Further study is in progress.One of us (BBS) acknowledges the support by the De-partment of Science and Technology(DST), New Delhi,for this research work, in the form of Young Scien-tist’s award under SERC Fast Track Scheme, vide letterNo.SR/FTP/PS-013/2011.

0 4 8 12 16 20

20

40

60

80

100

120

140

160

0 4 8 12 16 20

10-4

10-2

100

102

Ec.m.= 24 MeV

ECN*= 55.143 MeV

T = 5.2115 MeV

Ec.m.= 24 MeV

ECN*= 55.143 MeV

T = 5.2115 MeV

00

18F12C

8Be

18F

16O

14N10B6Li

4He

V (M

eV)

Fragment Mass A

10B+10B 20Ne* A1+A

2

2H

(a)

15

l(h)

(a)

16O

2H4He

6Li 14N8Be 12C

10B

Fragment Mass A

Pref

ormatio

n Pr

obabili

ty P

0

15

l(h)

10B+10B 20Ne* A1+A

2(b)

0 4 8 12 16 20

20

40

60

80

100

120

140

160

0 4 8 12 16 20

10-4

10-2

100

102

Ec.m.= 25.143 MeV

ECN*= 51.593 MeV

T= 4.9214 MeV

20Ne

20Ne1n11B 0

15

l(h)

13C8Be

10B

V (M

eV)

Fragment Mass A

0

15

l(h)

10B+11B 21Ne* A1+A

2(d)

Ec.m.= 25.143 MeV

ECN*= 51.593 MeV

T= 4.9214 MeV

11B10B1n

0

8Be 13C

Fragment Mass A

Pref

orm

ation

Prob

ability

P0

10B+11B 21Ne* A

1+A

2(c)

0 4 8 12 16 20 24

20

40

60

80

100

120

140

160

0 4 8 12 16 20 24

10-4

10-2

100

102

18F4H

8Li 14N

21Ne

Ec.m.= 24 MeV

ECN*= 49.361 MeV

T = 4.7029 MeV

0

0

14N8Li

21Ne

18F11B11B

4H

V (M

eV)

Fragment Mass A

1n

15

l(h)11B11B1n

Ec.m.= 24 MeV

ECN*= 49.361 MeV

T = 4.7029 MeV

Fragment Mass A

Pref

orm

atio

n Pr

obab

ility

P0

15

l(h)

11B+11B 22Ne* A1+A

2(e)

11B+11B 22Ne* A

1+A

2(f)

FIG. 1: The fragmentation potentials and preformation prob-ability for the decay of 20,21,22Ne∗ at different l-values .

∗email: [email protected]; Department of Physics, SriGuru Granth Sahib World University, Fatehgarh Sahib-06, INDIA.

[1] Raj. K. Gupta, et al., IREPHY 2 (2008) 369, Clus-ters in Nuclei,Lecture Notes in Physics, 818 (210)223, Ed. C. Beck and Springer. Verlag. Berlin. Heidel-berg, Proc. DAE Symp.on Nuc. Phys., 57 (2012) 550;

Proc.int.DAE Symp.on Nuc.Phys., 58 (2013) Accepted.[2] A. Zanto de Toledo, et al., PRL 62 (1989) 1255.

84

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FUSION14

Dynamical decay of 32S∗ and31P∗ formed in 20Ne+12C and 19F+ 12C reactions,respectively, at E∗

CN = 60MeV

BirBikram Singh,1, ∗ Mandeep Kaur,1 and Raj K.Gupta2

1Department of Physics, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140406,INDIA.2Department of Physics, Panjab University, Chandigarh-160014,INDIA.

Recently extensive efforts have been made to under-stand the reaction dynamics of very light nuclear sys-tem (A ∼ 30) formed in light heavy ion reactions. Gen-erally, here decay mechanism is interepted in terms offusion-Fission (FF) process or deep inelastic (DI) orbit-ing mechanism [1]. In case of FF process equilibratedcompound nucleus(CN) is formed, which decays, depend-ing on the available phase space and barrier penetrationprobabilities, into various exit channels.However, DI or-biting is referred to as the formation of a long lived din-uclear molecular complex with a strong memory of en-trance channel.It is intersting to note that both FF andDI orbiting occur on similar time scale.In the present study, the decay of very light nuclear sys-tem 32S∗ and 31P∗ formed in 20Ne+12C and 19F+12Creactions, respectively, at E∗CN=60 MeV is being stud-ied using the Dynamical Cluster decay Model(DCM) ofGupta and collabrators [2].The DCM has been applied successfully to the decay ofvery light, light, medium, heavy, superheavy mass com-pound nuclei for their decay to light particles(evaporationresidues), FF, quasi-fission (QF) depending upon the re-action conditions.Here, we look for the mechanism to ex-plain DI orbiting phenomenon within the DCM and tostudy its competition with FF process, as the experi-mental study [1], has shown DI orbiting phenomenon for20Ne+12C reaction dominant in comparison to the FFprocess which override the former for the 19F+12C reac-tion.The preliminary results as shown in fig.1 show theasymmetric decay of both the compound system and itwill be quite interesting to see the role of penetrationprobability further.Study is in progress.

0 5 10 15 20 25 30 35

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35

10-4

10-2

100

102

30P

31P

28Si

26Al

24Mg

22Na

20Ne

18F

16O

14N

12C

10B

4He

2H

1H

Ec.m.= 41.063 MeV

ECN*= 60 MeV

T = 4.2522 MeV

0

0

8Be

6Li

V (M

eV)

Fragment Mass A

20Ne+12C 32S* A1+A

2(a)

20

l(h)

20Ne+12C 32S* A1+A

2(b)Ec.m.= 41.063 MeV

ECN*= 60 MeV

T = 4.2522 MeV

Fragment Mass A

Pref

orm

atio

n Pr

obab

ility

P0

20

l(h)

0 5 10 15 20 25 30 35

0

20

40

60

80

100

120

0 5 10 15 20 25 30 3510-7

10-5

10-3

10-1

101

103

23Na

Ec.m.= 37.161 MeV

ECN*= 60 MeV

T = 4.3253 MeV

00

V (M

eV)

Fragment Mass A

25Mg21Ne

19F12C

10B

4He8Be

6Li

21

l(h)

19F+12C 31P* A

1+A

2(d)Ec.m.= 37.161 MeV

ECN*= 60 MeV

T = 4.2522 MeV

Fragment Mass A

Pref

orm

atio

n Pr

obab

ility

P0

21

l(h)

19F+12C 31P* A1+A

2(c)

FIG. 1: The fragmentation potentials and preformation prob-ability for decay of 32S∗ and 31P ∗ at different l-values

One of us (BBS) acknowledges the support by the De-partment of Science and Technology(DST), New Delhi,for this research work, in the form of Young Scien-tist’s award under SERC Fast Track Scheme, vide letterNo.SR/FTP/PS-013/2011.∗email: [email protected]; Department of Physics, Sri

Guru Granth Sahib World University, Fatehgarh Sahib-06,INDIA.

[1] AparajitaDey, et al., PRC 76 (2007) 034608; S.Kundu, etal., PRC78 (2008) 044601; T. K. Rana, et al., PRC 78(2008) 027602.

[2] Raj. K. Gupta ,et al., IREPHY 2 (2008) 369, Clus-ters in Nuclei, Lecture Notes in Physics, 818 (210)

223, Ed. C. Beck and Springer. Verlag. Berlin. Heidel-berg, Proc. DAE Symp.on Nuc. Phys., 57 (2012) 550;Proc.int.DAE Symp.on Nuc.Phys., 58 (2013) Accepted.

85

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FUSION14

Observation of in-complete fusion at low angular momentum values

Devendra P. Singh,1, ∗ Vijay R. Sharma,1 Abhishek Yadav,1 Pushpendra. P.Singh,2 Unnati,1 M. K. Sharma,3 Rakesh Kumar,4 B. P. Singh,1 and R. Prasad1

1Department of Physics, Aligarh Muslim University, Aligarh (U.P.)-202002, India2GSI Helmholtz Centre for Heavy Ion Research GmbH, D-64291 Darmstadt, Germany

3Physics Department, S. V. College, Aligarh (U.P.), India4NP-Group: Inter University Accelerator Centre, New Delhi-110067, India

The study of heavy ion (HI) reaction mechanism atnear barrier energies has been a topic of interest. One ofits main motivations is concerned with the rich interplaybetween different reaction processes and how they influ-ence one another. The effect of breakup of HIs on fusionhas been investigated in recent years both experimentally[1, 2] and theoretically, however, these are not clearly un-derstood. The analysis of experimentally measured exci-tation functions within the framework of statistical modelcodes may be used to obtain the information about thereaction mechanisms involved. Interestingly, α-emittingchannels at energies as low as ≈3-6 MeV/A are foundto show enhancement of cross-sections over the statisti-cal model predictions, which may be due to the projectilebreak-up processes in these reactions. In HI reaction pro-cesses, the direct α-particles have been observed in theforward cone with nearly the same velocity as that of theincident ion. These are refereed to as originating from in-complete fusion (ICF) reactions [1, 2]. Though, at higherprojectile energies (≥ 10MeV/A), Wilczynski et al. [3]have well explained the cross-sections for ICF reactionsbased on partial statistical equilibrium and on the ideaof generalized concept of angular momentum. However,on the basis of above prescription, ICF reactions couldnot be explained at lower projectile energies, where, themaximum angular momentum values (ℓmax) are less thanthe critical angular momentum (ℓcrit), in general. The γ-multiplicity measurements also indicate that such break-up fusion involves ℓ ≥ ℓcrit. However, studies on sphericaltargets showed involvement of ℓ-values in ICF lower thanℓcrit as well, giving rise to conflicting reports [4, 5], on thedependence of ICF on the angular momentum. Further,no clear picture for low energy ICF dependence on pro-jectile energy, mass asymmetry etc., has been found. Inorder to explore some of the above aspects, experimentshave been performed at the IUAC, New Delhi, India for16O + 130Te system.

The cross-sections for the reaction residues 141Nd (5n),139Ce (α3n), 133m,gXe (3αn) and 131mXe (3α3n) have

been measured and analyzed within the framework oftheoretical model code PACE4, in which ICF of the in-cident ion is not taken into consideration. Analysis ofthe data indicates significant enhancement of measuredcross-sections for α-emitting channels as compared to

0 10 20 30 40 50 600

10

20

30

40

50

60

Fig. 1 Fusion l-distributions for 16O + 130Te system

crit= 53

(mb)

( )

max = 23 61 MeV

max = 48 90 MeV

the statistical model predictions, at energies as low as≈3 MeV/A. In order to ascertain the involvement of ℓ-distribution in 16O+130Te system, the ℓcritical value hasbeen calculated and is found to be ≈53~. The fusionℓ-distributions have also been calculated using the codeCCFULL [6] at 61 and 90 MeV energies. The ℓmax valuesat these energies are found to be≈ 23 & 48 ~, respectivelyas shown in figure, which are less than the ℓcrit for fusioneven at the highest studied energy for the present system.As such, the ICF contributions are expected to be negli-gible at these energies as per the Wilczynski prescriptions[3]. The present analysis suggests that a significant num-ber of partial waves below ℓcrit may contribute to ICFchannels, which suggest a diffused boundary in ℓ-space.Further, details of the measurement and analysis will bepresented.∗corresponding author: [email protected]

[1] M. Dasgupta et al., Phys. Rev. C 66, 041602(R) (2002).[2] D. P. Singh et al., Phys. Rev. C 80, 014601 (2009).[3] J. Wilczynski et al.; Phys. Rev. Lett. 45, 606 (1980).[4] A. Yadav et al., Phys. Rev. C 85, 034614 (2012); Phys.

Rev. C 85, 064617 (2012).

[5] I. Tserruya et al.; Phys. Rev. Lett. 60, 14 (1988).[6] K. Hagino et al.; Computer Physics Communications 123,

143 (1999).

86

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FUSION14

Effect of the target deformation on incomplete fusion dynamics

D. Singh,1, ∗ Rahbar Ali,2 M. Afzal Ansari,3 R. Kumar,4 R. P. Singh,4 S. Muralithar,4 and R. K. Bhowmik4

1Centre for Applied Physics, Central University of Jharkhand, Ranchi 835205, India2Department of Physics, G. F. (P. G.) College, Shahjahanpur 242001, India3Department of Physics, Aligarh Muslim University, Aligarh 202002, India

4Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India

Study of incomplete fusion dynamics induced by heavyions with the deformed and spherical targets has beena growing interest at energies above Coulomb barrier[1, 2]. Observations show that at projectile energiesabove the Coulomb barrier, both the processes completefusion (CF) and incomplete fusion (ICF) may be con-sidered as dominant reaction mechanisms. Semi-classicaltheory of heavy ion interaction says that the CF andICF processes may be categorized on the basis of driv-ing input angular momentum imparted in the system. InCF process the driving input angular momentum, in ac-cordance with sharp cut-off approximation and may beunderstood in the following way: In CF, the attractivenuclear potential overcomes the repulsive Coulomb andcentrifugal potentials in central and near central colli-sions. Consequently, CF takes place at a small impactparameter value where as the formation of fully equili-brated compound nucleus takes place. However, at rel-atively higher values of impact parameter, the repulsivecentrifugal potential increases and hence the dominanceof attractive nuclear potential ceases to capture entireprojectile. Therefore, an incompletely fused compositesystem comprising of a part of projectile plus the targetappears in the exit channel that leads to ICF process,wherein the involvement of driving input angular mo-mentum is relatively larger than that of needed for CFprocess to take place. At this stage if the driving inputangular momentum exceeds the critical limit for CF, nofusion can occur unless a part of the projectile is emittedto release excess driving input angular momentum. Assuch, prompt emission of a part of projectile takes placeto provide sustainable input angular momenta to the sys-tem. After such an emission, the resulting input angularmomenta carried by the remnant projectile is less thanor equal to its own critical angular limit for fusion tooccur with the target nucleus. Various dynamical mod-els have been proposed to explain the mechanism of ICFreactions. However, no theoretical model is available toexplain the gross features of experimental data availablebelow E/A=10 MeV. Most of the ICF reaction studies bycharged particle-gamma coincidence technique have been

carried out with low-Z (Z≤10) projectile induced reac-tions on heavy targets (A≥150). However, with mediummass target nuclei, such information is scarce. To inves-tigate the role of target deformation on ICF dynamics,an experiment has been performed using Gamma detec-tor array coupled with charged particle array at InterUniversity Accelerator Centre, New Delhi. Spin distri-butions for various evaporation residues populated viacomplete and incomplete fusion of 16O with 124Sn at 6.3MeV/nucleon have been measured. Using charged par-ticles (Z=1, 2)-γ coincidence technique, prompt γ-rayshave been recorded in coincidence with fast α-particle(s)emitted in forward cone, in the break-up of the projectile16O in the nuclear field, and such evaporation residueshave been identified as incompletely fused products. Ex-perimentally measured spin distributions of the residuesproduced as ICF products associated with fast α and 2α-emission channels observed in forward cone are found tobe distinctly different from that of the residues producedas CF products. The mean value of input angular mo-mentum J0 for evaporation residues produced throughxn channels (CF products) is found to be J0 ≈ 7~ whilethe mean value of input angular momentum J0 for theresidues produced through direct αxn and 2αxn chan-nels (ICF products) in forward cone, are found to be J0

≈ 9~ and ≈ 12~ respectively for 16O + 124Sn (spherical)system, while the mean value of input angular momentaJ0 is reported in Ref. [1], for the system 16O + 169Tm(deformed) are found to be ≈10 ~ for xn-channels (CFproducts) and for direct αxn and 2αxn channels (ICFproducts) the value of J0 approaches to ≈ 13~ and ≈16~, respectively. The values of the input angular mo-mentum observed for xn (CF products), αxn and 2αxn(ICF products) in 16O + 124Sn (spherical) system aresmaller than that input angular momentum observed forxn(CF products), αxn and 2αxn (ICF products) in 16O+ 169Tm (deformed) system. The comparison of data in-ferred that input angular momentum are smaller in caseof spherical target than that of deformed target at sameprojectile energy of 16O ion beam. It means that the ICFdynamics depends on the target deformation.∗[email protected]

[1] P. P. Singh et al., Physics Letters B 671, 20 (2009).[2] D. Singh, et al., Phys. Rev. C 81, 027602 (2010).

87

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FUSION14

Fission excitation function for 19F + 194,196,198Pt at near and above barrier energies

Varinderjit Singh,1, ∗ B.R. Behera,1 Maninder Kaur,1 M. Oswal,1 K.P. Singh,1 A.Jhingan,2 P. Sugathan,2 Santanu Pal,3 D. Siwal,4 S. Goyal,4 A. Saxena,5 and S. Kailas5

1Department of Physics, Panjab University, Chandigarh 160014, India.2Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.

3CS-6/1, Golf Green, Kolkata 700095, India.4Department of Physics and Astrophysics, University of Delhi 110007, India.

5Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.

Nowadays the presence of Kramers’ predicted nucleardissipation is well established [1]. The nuclear dissipationis mainly observed in the heavy ion induced fusion-fissionreactions. It can influence the capture probability of pro-jectile by target and deexcitation of excited compoundnucleus (CN). Hence it becomes necessary to understandthe nature and magnitude of dissipation. Mostly studiesabout the nuclear dissipations are based on the neutronand charged particle multiplicity measurements. Theseprobes are sensitive to the dissipation over the whole pathof fission process i.e. from equilibrium to scission andhence cannot distinguish the pre-saddle and post-saddledissipation (deformation dependence of nuclear dissipa-tion). Since the decision whether the CN will undergofission or will results in formation of evaporation residueis taken at saddle point, hence the fission and evapora-tion residue (ER) cross-sections are sensitive to only dis-sipation within the saddle point. Here it must be addedthat the above statement holds in the absence of non-compound processes (quasi or fast fission). In our earlierstudy of neutron multiplicity for 19F + 194,196,198Pt reac-tions, it has been observed that the non-compound nu-clear processes are negligible for these reactions [2, 3].So the measurement of fission cross-sections for thesereactions can be use to get the information about thepre-saddle dissipation. With this motivation the fissionangular distribution (fission cross-section) has been mea-sured for 19F + 194,196,198Pt at beam energy range 90-118MeV.

The measurement was carried out at General PurposeScattering Chamber (GPSC) at Inter University Accel-erator Center (IUAC), New Delhi. Two different type oftelescope detectors were used, one having both 4E-E Sisurface barrier (SSB) detectors and other using 4E gasdetector followed by E SSB detector (hybrid telescopedetectors). The measurements were done independentlyfrom one another so that working of both telescope detec-tors can be compared. The fission angular distributiondata was recorded at angle range 78o-169o. Two SSB de-

tectors were kept at ± 10o with respect to beam directionfor monitoring and normalization purpose.

The absolute fission cross-sections can be obtained as

dΩfiss

=1

2

Yfiss

Ymon

Ωmon

Ωfiss

dΩmon

(1)

where Yfiss and Ymon is fission and monitor yield, Ωfiss

and Ωmon is the solid angle of fission and monitor de-tectors respectively. Also dσ/dΩmon is the Rutherfordcross-sections. The experimentally obtained ratio of fis-sion to monitor yield has been fitted with theoretical ex-pression for fission angular distribution. The fission yieldhas been integrated to get the total fission cross-sections.

It is observed that the fission cross-sections obtainedby both (SSB and Hybrid) telescope detectors are match-ing within error bars. The fission cross-sections increasesmarginally as one moves from 217Fr to 213Fr. The exper-imentally obtained fission cross-sections has been com-pared with the statistical model calculations. In the sta-tistical model calculations, along with fission, emission ofneutron, proton, α, GDR γ-ray and evaporation residueare considered as possible decay channels. The exper-imental masses are used for calculating particle bind-ing energies and shell corrected fission barrier has beenused [3]. The spin distribution has been obtained by fit-ting the experimental fusion cross-section with coupledchannel calculations based code CCDEF [4]. It is ob-served that statistical model calculations under predictthe experimental fission cross-section and fission barrierhas been lowered to fit the experimental fission cross-sections. This indicates that the nuclear dissipation isabsent in pre-saddle region, but a considerable dissipa-tion has been observed for neutron multiplicity measure-ment. So, more theoretically studies with better mod-elling of fission and use of different dissipation strengthin pre-saddle and post-saddle (shape dependent dissipa-tion) dissipations may remove the apparent contradictionbetween the results from fission and neutron analysis.

∗corresponding author: Mangat [email protected]; Present ad-

dress:GSI Helmholtzzentrun fur Schwerionenforschung GmbH,64291 Darmstadt, Germany.

[1] D. Hilscher and H. Rossner, Ann. Phys. (Paris) 17, 471(1992).

[2] Varinderjit Singh et al., Phys. Rev. C 86, 014609 (2012).[3] Varinderjit Singh et al., Phys. Rev. C 87, 064601 (2013).

[4] J. Fernandez Niello, et al., Comput. Phys. Commun. 54,409 (1989).

88

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FUSION14

Spin distribution measurement of 64Ni + 100Mo at near and above barrier energies

Varinderjit Singh,1, ∗ D. Ackermann,2 S. Antalic,3 M. Axiotis,4 D. Bazzacco,5 L. Corradi,4 G.De. Angelis,4 E. Farnea,5 A. Gadea,4 F.P. Heßberger,2 M.G. Itkis,6 G.N. Kniajeva,6 E.M.

Kozulin,6 T. Martinez,4 N. Marginean,6 R. Menegazzo,5 G. Montagnoli,5 D.R. Napoli,4 Yu. Ts.

Oganessian,6 M. Ruan,7 R.N. Sagaidak,6 F. Scarlassara,5 A.M. Stefanini,4 S. Szilner,4 and C. Ur5

1Department of Physics, Panjab University, Chandigarh 160014, India.2GSI Helmholtzzentrun fur Schwerionenforschung GmbH, 64291 Darmstadt, Germany.

3Comenius University of Bratislava, Slovakia.4INFN, Laboratori Nazionali di Legnaro, Legnaro (PD).

5Dipartimento di Fisica and INFN Padova.6JINR Flerov Laboratory of Nuclear Reaction, Dubna, Russia.

7Institute of Atomic Energy, Beijing, China.

In the last decades, a number of measurements havebeen performed to understand the fusion reaction dy-namics and to obtain an experimental representation ofbarrier distribution using precisely measured fusion exci-tation functions [1]. As an alternative apporach to thisthe employment of the compound nucleus (CN) spin dis-tribution (SD) was proposed [2]. To explore the aspectslike the fusion-fission competition, the role of deforma-tion in fusion of a heavy system and the possible ef-fect of Z=82 shell closure on enhancement of evapora-tion residue (ER) cross-sections, a series of experimentshave been performed to measure the SD for 64Ni, 34S and48Ca induced reactions using the γ detector array GASPat the Laboratori Nazionali di Legnaro, Italy. The GASParray consists of 80 BGO detectors (total efficiency ≈ 80% as a multiplicity filter) and 40 HPGe detectors (usedfor identification of ERs).

In the present work, we are reporting the results ofour first experiment based on the SD measurement ofthe reaction 64Ni + 100Mo at beam energies ranging from230 MeV to 260 MeV. This measurement was motivatedby an earlier study for the same reaction using the Ar-gonne/Notre Dame BGO array, where it was observedthat possibally fission affects the SD. But in that mea-surement the SD was obtained for a global ER coinci-dence without ER identification, in contrast to that inthe present work we were sensitive to single ER chan-nels.

The experimentally recorded data is used to obtainthe fold distribution of each ER channel by gating thefold spectrum with respective characteristic γ transitions.The experimentally obtained fold distributions are con-verted into multiplicity distributions using the responsefunction of the detector array. Finally the multiplicitydistributions are converted to SDs using eq. 2 in Ref.

[3]. The spin removed by γ transition close to the yrastline is obtained by averaging the spin of M1, E1 and E2transitions of the excitation scheme of the respective ERchannel. The spin removed by statistical γ rays and evap-orated particles is obtained from the statistical modelcode PACE2, and the ground state spin is taken fromnuclear data sheets. The integral fusion cross-sectionsare also taken from PACE2 calculations. The total SDat each energy is obtained as the sum of the SD for thesingle ER channels. The comparison of the SDs at differ-ent beam energies is shown in Fig. 1. It is observed thatthe high spin tail of the SD becomes steeper and steeperwith increasing beam energy. With increasing beam en-ergy fission starts competing with ER production andthe partial wave with higher spin end up as fission whichresults in cutting of the SD at the high spin end.

FIG. 1: A comparison of the spin distribution at differentbeam energies.

∗corresponding author: Mangat [email protected]; Guest Sci-

entist@GSI Helmholtzzentrun fur Schwerionenforschung GmbH,64291 Darmstadt, Germany.

[1] M. Dasgupta et al., Ann. Rev. Nucl. Part. Sci., 48, 401(1998).

[2] D. Ackermann et al., Eur. Phys. J. A 20, 151 (2004), D.

Ackermann, Acta Physica Polonica B 26, 517 (1995).[3] A.M. Stefanini et al., Nucl. Phys. A 548, 453 (1992).

89

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FUSION14

Microscopic calculation of astrophysical S-factor and branching ratio of the reaction3H(α, γ)7Li

A.S. Solovyev,1, ∗ S.Yu. Igashov,1 and Yu.M. Tchuvil’sky2

1All-Russia Research Institute of Automatics, 127055 Moscow, Russia2Scobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991 Moscow, Russia

The fully microscopic approach – the algebraic versionof the resonating group model (AVRGM) [1, 2] was ap-plied to study the fusion process 3H(α, γ)7Li. This reac-tion is of great importance for the models of nucleosyn-thesis. At low energies the experimental data have largeerrors [3–7] and thus occur to some extent unreliable be-cause the cross sections drop down exponentially as theenergy is decreased. So theoretical extrapolations anddirect calculations turn out to be the only way to obtainthe cross sections and S-factors at the energies typical forthe astrophysics. Microscopic approaches to the problemsignificantly improve the reliability of results.

Here we calculate the radiative capture cross section(S-factor) with the wave functions (WF) obtained inAVRGM approach. In this model the total WF of asystem is sought in the form of antisymmetrized prod-uct of the internal wave functions of clusters and the WFof relative motion. In the algebraic version in contrastto the conventional RGM the WF of relative motion issought in the form of expansion in the series of oscilla-tor functions. The Hasegawa–Nagata NN-potential [8]is used in our study. The calculated astrophysical S-factor and branching ratio R = σ1/σ0, where the crosssections σ0 and σ1 are related to the transitions to the

ground and the first excited states of 7Li nucleus respec-tively, turn out to be in a reasonable agreement with theexperimental data [3, 4, 7] all over the energy range ofmeasurements (Fig. 1).

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

S (

keV

b)

Ref. [3] Ref. [4] Ref. [5] Ref. [7] AVRGM

0.000.100.200.300.400.500.600.70

0.0 0.2 0.4 0.6 0.8 1.0 1.2

R

E (MeV)

FIG. 1: Comparison of S-factor and branching ratio R withexperimental data.

∗corresponding author: [email protected]

[1] G. Filippov and I. Okhrimenko, Phys. Atom. Nucl. 32,480 (1980).

[2] G. Filippov, Phys. Atom. Nucl. 33, 488 (1981).[3] G. M. Griffiths, R. A. Morrow, P. J. Riley, and J. B. War-

ren, Canadian Journal of Physics 39, 1397 (1961).[4] S. Burzynski, K. Czerski, A. Marcinkowski, and

P. Zupranski, Nucl. Phys. A 473, 179 (1987).[5] U. Schroder, A. Redder, C. Rolfs, R. E. Azuma, L. Buch-

mann, C. Campbell, J. D. King, and T. R. Donoghue,Phys. Lett. B 192, 55 (1987).

[6] H. Utsunomiya, Y.-W. Lui, D. R. Haenni, H. Dejbakhsh,L. Cooke, B. K. Srivastava, W. Turmel, D. O’kelly, R. P.Schmitt, D. Shapira, J. Gomez del Campo, A. Ray,T. Udagawa, Phys. Rev. Lett. 65, 847 (1990).

[7] C. R. Brune, R. W. Kavanagh, and C. Rolfs, Phys. Rev.C 50, 2205 (1994).

[8] H. Kanada, T. Kaneko, S. Nagata, and M. Nomoto, Progr.of Theor. Phys. 61, 1327 (1979).

90

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FUSION14

Structure of 26Al studied by one-nucleon transfer reaction 27Al(d,t)

Vishal Srivastava,1, ∗ C. Bhattacharya,1 T.K. Rana,1 S. Manna,1 S. Kundu,1 S. Bhattacharya,1 K.Banerjee,1 P. Roy,1 R. Pandey,1 G. Mukherjee,1 T.K. Ghosh,1 J.K. Meena,1 T. Roy,1 A. Chaudhuri,1 M.

Sinha,1 A. Saha,1 J. Sahoo,1 R. Saha Mondal,1 Md. A. Asgar,1 Subinit Roy,2 and Md. Moin Shaikh2

1Variable Energy Cyclotron Centre,1/AF, Bidhan Nagar, Kolkata 700064, India2Saha Institute of Nuclear Physics,1/AF, Bidhan Nagar, Kolkata 700064, India

Transfer reaction provides a powerful tool to studythe structure of nuclei. The study of structure of 26Alis important in many different fields of nuclear physicsas well as in astrophysics. In each case, the specificaspects of structure of 26Al nucleus, e.g., excitationenergies, spin, and parity assignments, branching ratios,spectroscopic factors and life times are required.

FIG. 1: Two dimensional ∆E - E plot obtained using Si (55µm)- Si (1030 µm ) combination for the d (25 MeV) + 27Alreaction at the angle θlab = 35.

Though, many of these specifics are known [1], yet,there are possibilities to search new levels for 26Al . Veryrecently, five new levels of 26Al have been identified usingthe reaction 28Si(p,3He) [2]. The structure of 26Al hadalready been studied by two - nucleon transfer channelsusing the reactions 28Si(d,α) and 24Mg(3He,p) [3], andcomparative study of two nucleon pickup and stripping

channels have been made.

Recently, we have studied the structure of 26Al by sin-gle nucleon transfer reaction using 27Al(d,t) channel withthe motivation to study the cross sections for transfer tovarious final states in 26Al and to compare it with thoseproduced via two nucleon transfer reaction channels andalso to search for any new states at higher excitationsin 26Al. Here, we report preliminary results of our mea-surements on the structure of 26Al produced via 27Al(d,t)reaction.

The experiment was performed using deuteron beamof energy 25 MeV from the Variable Energy Cyclotronat VECC, Kolkata. The target was a self - supporting27Al foil ( 140 µg/cm2). The angular distributions oftransfer channels were measured using a three - elementtelescope, consisting of a single - sided 55 µm thick Si(∆E) strip detector (16 vertical strips of 3 mm width),followed by a double - sided 1030 µm Si (E) strip detector(16 strips, width 3 mm, both side mutually orthogonalto each other) backed by four CsI(Tl) detectors, each ofthickness 6 cm. A 6 mm horizontal slit was placed infront of the telescope. The solid angle subtended by eachstrip was 0.7 msr. The angular distributions have beenmeasured in the angular range of 14 to 40 in the stepof 0.9. Well separated ridges corresponding to differentoutgoing particles as well as excited states correspondingto the nuclei 26Al, 26Mg, and 25Mg produced via thereaction channels 27Al(d,t), 27Al(d,3He) and 27Al(d,α)are clearly seen in ∆E- E scatter plot (Fig. 1) measuredat an angle 35. Calibration of each detectors have beendone using Th - α source. Further analysis is in progressto extract the excitation energy spectrum of 26Al, byprojecting the tritium band. Angular distributions ofeach known states will be extracted and will be comparedwith those obtained from two-nucleon transfer channels[3].∗corresponding author: [email protected]; Permanent ad-

dress:Variable Energy Cyclotron Centre, Kolkata 700064, India

[1] P. M. Endt et al ., Nucl. Phys. A 633, 1(1998).[2] K. A. Chipps et al ., Phys. Rev. C 86, 014329(2012).

[3] N. Takahashi et al ., Phys. Rev. C 23, 1305(1981).

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FUSION14

Transfer couplings and hindrance far below the barrier in the fusion of 40Ca + 96Zr

A.M. Stefanini,1, ∗ G. Montagnoli,2 H.Esbensen,3 L.Corradi,1 S.Courtin,4 E. Fioretto,1 A.Goasduff,5 J.Grebosz,6 F. Haas,4 M.Mazzocco,2 C.Michelagnoli,2 T. Mijatovic,7 D.Montanari,2

G.Pasqualato,2 C.Parascandolo,2 F. Scarlassara,2 E.Strano,2 S. Szilner,7 and D.Torresi21INFN, Laboratori Nazionali di Legnaro, Legnaro, Padova, Italy

2Dip. di Fisica e Astronomia, Univ. di Padova, and INFN, Sez. di Padova, Padova, Italy3Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA

4IPHC, CNRS-IN2P3, Universite de Strasbourg, F-67037 Strasbourg Cedex 2, France5CSNSM, CNRS/IN2P3 and Universite Paris-Sud, F-91405 Orsay Campus, France

6Institute of Nuclear Physics, Polish Academy of Sciences, PL 31-342 Cracow, Poland7Ruder Boskovic Institute, HR-10002 Zagreb, Croatia

10-3

10-2

10-1

100

101

102

103

85 90 95 100 105 110 115

f (m

b)

Ecm (MeV)

40Ca +

96Zr

NewCh-1

Ch-16Ch-23Ch-69

0

0.5

1

1.5

2

2.5

3

85 90 95 100 105

L(E

c.m

.)

[MeV

-1]

Ec.m. (MeV)

Constant S

40Ca +

96Zr

FIG. 1: Fusion excitation function and its logarithmic deriva-tive, compared to CC calculations (see text).

The fusion excitation function of 40Ca + 96Zr has beenmeasured down to σ '2.4µb, that is, much smaller thanobtained in a previous experiment [1], where sub-barrierfusion was found to be greatly enhanced with respect to40Ca + 90Zr, and the need of coupling to transfer chan-nels was suggested. We wanted to trace down the effect ofnucleon transfer couplings for deep sub-barrier energiesand to try disentangling the elusive interplay of inelasticcouplings, transfer couplings and, possibly, the appear-ance of the fusion hindrance [2]. 40Ca beams from theXTU Tandem accelerator of INFN-Laboratori Nazionalidi Legnaro were used. The excitation function is shown in

the upper panel of Fig. 1 where the present cross sectionsand those of Ref. [1] are plotted with red and black sym-bols, respectively. The excitation function is very smootheven far below the barrier; the logarithmic slope increasesslowly and remains well below the limit expected for aconstant S factor (lower panel). No indication of hin-drance shows up, and a comparison with 48Ca + 96Zr(where hindrance was observed [3, 4]) is illuminating inthis respect (see Fig. 2).

0.001

0.01

0.1

1

10

100

85 90 95 100

48Ca+96Zr

40Ca+96Zr new data

40Ca+96Zr Ref.[3]

σfu

s (

mb

)

Ecm

(MeV)

0

100

200

300

400

500

90 95 100 105 110

FIG. 2: Comparison with 48Ca + 96Zr [3].

CC calculations using Woods-Saxon potentials havebeen performed. Ch-1 (Fig. 1) is the no-coupling limit.Two and three phonons of the strong octupole mode in96Zr have been included (Ch-16 and Ch-23 lines), be-sides the weaker quadrupole modes, and their effect isvery strong. The low-energy cross sections of 40Ca +96Zr are strongly underpredicted. Further couplings toQ >0 one- and two-nucleon transfer channels (Ch-69)produce further cross section enhancements, even at thelevel of a few µb. The data, however, still exceeds thefull CC result at the lowest energies. Locating the hin-drance threshold, if any, in 40Ca + 96Zr would requirechallenging measurements in the sub-µb range.∗corresponding author: [email protected]

[1] H.Timmers et al., Nucl. Phys. A 633 (1998) 421.[2] C. L. Jiang et al., Phys. Rev.Lett. 89 (2002) 052701.[3] A.M.Stefanini et al., Phys. Rev. C 73 (2006) 034606.

[4] H. Esbensen, C.L.Jiang, Phys. Rev. C 79 (2009) 064619.

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FUSION14

Fusion hindrance and quadrupole collectivity in collisions of A'50 nuclei

A.M. Stefanini,1, ∗ G. Montagnoli,2 L.Corradi,1 S.Courtin,3 D.Bourgin,3 E.Fioretto,1 A. Goasduff,4 J.Grebosz,5 F. Haas,3 M.Mazzocco,2 T. Mijatovic,6

D.Montanari,2 C.Parascandolo,2 F. Scarlassara,2 E.Strano,2 S. Szilner,6 and D.Torresi21INFN, Laboratori Nazionali di Legnaro, Legnaro, Padova, Italy

2Dip. di Fisica e Astronomia, Univ. di Padova, and INFN, Sez. di Padova, Padova, Italy3IPHC, CNRS-IN2P3, Universite de Strasbourg, F-67037 Strasbourg Cedex 2, France4CSNSM, CNRS/IN2P3 and Universite Paris-Sud, F-91405 Orsay Campus, France

5Institute of Nuclear Physics, Polish Academy of Sciences, PL 31-342 Cracow, Poland6Ruder Boskovic Institute, HR-10002 Zagreb, Croatia

0.001

0.01

0.1

1

10

100

-8 -6 -4 -2 0 2 4 6 8

58Ni + 54Fe

48Ti + 58Fe (prelim.)

σfu

s (

mb

)

Ec.m.

- Vb (MeV)

0

0.04

0.08

0.12

0.16

-5 0 5

48Ti + 58Fe (prelim.)

58Ni + 54Fe

BD

(M

eV

-1)

Ec.m.

- Vb (MeV)

FIG. 1: Fusion excitation functions (up) and barrier distribu-tions (down) of 48Ti + 58Fe and of 58Ni + 54Fe [6].

Multi-phonon excitations become dominant in thenear-barrier fusion of medium-heavy nuclei and producecomplex barrier distributions [1]. At deep sub-barrier en-ergies, the excitation functions show a sharp decrease [2],well below the expectations based on standard coupled-channels (CC) calculations (hindrance). This should bea general phenomenon in heavy-ion fusion. However, itsenergy threshold strongly depends on the structure of the

colliding nuclei, being in general lower for soft systems,whose barrier distribution may extend to lower energies,with respect to rigid or closed-shell nuclei, thereby ”coun-terbalancing” hindrance. This was observed, e.g., in thecomparison of 58Ni + 58Ni with 64Ni + 64Ni [3]. In theA = 40-60 mass range, a few systems were investigatedat LNL in recent years (the Ca+Ca systems [4], 36S +48Ca [5], 58Ni + 54Fe [6]). All of them involve closed-shell nuclei, and show hindrance, with different strengthsand features. Collective vibrations are known in sev-eral nuclei in this mass region, although not so strong asfor heavier cases. The case of 32S + 48Ca [7] is differ-ent: no hindrance effect has been observed down to thesub-µb cross section level. Actually, the rather strongquadrupole mode of 32S, together with positive Q-valuetransfer couplings, may be responsible for this behavior.We found that the system 48Ti + 58Fe is appealing, sinceboth nuclei have a low-lying quadrupole excitation: the2+ states lie at ≈800-900 keV only, while the octupolestates are high and rather weak. We performed very re-cently a first measurement of the excitation function ofthis system, using the 48Ti beams from the XTU Tan-dem of the LNL, and our set-up for detection of evapo-ration residues based on a beam electrostatic deflector.The preliminary result is shown in Fig. 1 (blue dots). Itis compared, in an energy scale relative to the Akyuz-Winther barrier Vb, with the cross sections of 58Ni +54Fe [6] (closed-shell nuclei), where the hindrance effectsets in at the relatively large cross section of ≈200 µb. Ifconfirmed by the final data analysis (including two lowerenergy points), Fig. 1 indicates a parallel behavior downto ∼10µb, contrary to naıve expectations. However, thetwo barrier distributions Fig. 1 (lower panel) have similaroverall widths, but the case of 48Ti + 58Fe is more flatand structureless. This is what we expect for stronger,and lower in energy, inelastic couplings.

∗corresponding author: [email protected]

[1] A.M.Stefanini et al., Phys. Rev. Lett. 74, (1995) 864.[2] C. L. Jiang et al., Phys. Rev.Lett. 89 (2002) 052701.[3] C.L.Jiang et al., Phys. Rev. Lett. 93 (2004) 012701.[4] G. Montagnoli et al., Phys. Rev. C 85 (2012) 024607.

[5] A.M.Stefanini et al., Phys. Rev. C78 (2008) 044607.[6] A.M.Stefanini et al., Phys. Rev. C82 (2010) 014614.[7] G.Montagnoli et al., Phys. Rev. C87 (2013) 014611.

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FUSION14

Role of the Skyrme tensor terms in fusion thresholds

P. D. Stevenson1, ∗1Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH

The full version of the Skyrme force, including termsarising only from the Skyrme tensor force, is appliedto the study of collisions within a completly symmetry-unrestricted time-dependent Hartree-Fock implementa-tion.

We discuss the newly-released time-dependentHartree-Fock code, Sky3d [1], and explore the system-atic effect of varying the tensor terms of the Skyrmeinteraction [2, 3], which have been extensively studiedfor their role in single-particle structure.

We examine the effect on fusion thresholds and cross-sections with and without the tensor force terms and findan effect on the threshold energy of the order severalMeV. We conclude that the tensor terms play a suffi-ciently significant role in the dynamics of fusion to war-rant their inclusion in the Skyrme-like approach to theenergy density functional. We discuss open questions,such as the appropriate way to fit coupling strengths oftime-odd fields.

∗corresponding author: [email protected]

[1] J. A. Maruhn, P.-G. Reinhard, P. D. Stevenson andA. S. Umar, submitted to Comput. Phys. Commun.,arXiv:1310.5946 .

[2] S. Fracasso, P. D. Stevenson and E. B. Suckling, Phys.

Rev. C 86, 044303 (2012).[3] P. D. Stevenson, Sara Fracasso and E. B. Suckling, J.

Phys. Conf. Ser. 381, 012105 (2012).

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FUSION14

Fusion-fission studies around Coulomb barrier energies using IUAC facilities

P. Sugathan1, ∗ and IUAC Nuclear Physics Group1

1Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India

The study of fusion-fission dynamics using heavy ioninduced reactions has been a topic of considerable re-search interest for many years. The time scale involvedin these reaction has been extensively studied by variousprobes such as pre-scission neutrons and charged parti-cle multiplicities, evaporation residues, and giant dipolegamma rays. Contrary to the standard statistical modelpredictions, an excess of pre-scission multiplicities hasbeen measured in many fusion-fission reactions. This ex-cess emission from the highly excited compound systemhas been attributed to the hindrance or time delay in thedynamics fission process. The delay in the fission processmay also lead to a higher probability for survival of com-pound system and show up as an enhancement of evap-oration residue cross section than predicted by the stan-dard statistical model. Another well studied phenomenais the quasi fission process which is in direct competi-tion with fusion-fission. It has now been experimentallywell established that, competition from quasi fission pro-cess is dominant in heavier systems, thereby hinderingthe formation of super heavy systems in complete fu-sion reactions. Fission fragment mass distribution andthe measurement of pre-scission and post-scission neu-tron multiplicity in coincidence with fission fragment hasbeen used as a powerful tool to study the dynamics of thefissioning system and a large number of such experiments

have been performed.At Inter University Accelerator Centre(IUAC), New

Delhi, heavy ion beams from the tandem plus LINACaccelerator are used for fusion-fission reaction studiesaround the Coulomb barrier energies. Using DC andpulsed beams, we have performed a number of experi-ments probing the fusion-fission dynamics in our scat-tering chamber, recoil mass separator and neutron arrayfacility. The scattering chamber facility consist of 1.5m diameter vacuum chamber and a time of flight spec-trometer for fission fragment mass measurements. Theevaporation residue measurements are carried out usingrecoil mass separator along with ancillary detectors forgamma multiplicity measurements. The neutron detectorarray in its earlier stage consisted 24 liquid scintillatorsand a pair of multi-wire proportional counters(MWPC)for fission-fragment detection. These facilities have beenused for experiments measuring the evaporation residuecross section, fission fragment mass distribution, angulardistribution and extraction of pre and post scission neu-tron multiplicities. To enhance the scope of research inthis field using LINAC beams , new facilities consistingof 100 neutron detectors and dual mode (gas filled as wellas vacuum node) hybrid recoil separator has been addedto our research facilities. The facilities and the researchprograms will be presented in this talk.∗Email: [email protected]

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FUSION14

Probing nucleon-nucleon correlations via heavy ion transfer reactions

S. Szilner11Ruder Boskovic Institute, Zagreb, Croatia

Transfer reactions play an essential role in the study ofcollision dynamics and nuclear structure. They have animportant impact in the understanding of correlations inthe nuclear medium [1]. In the heavy-ion induced transferreactions, the constituents of the collision may exchangemany nucleons, thus providing information on the contri-bution of single particle and correlated particle transfers,and on the contribution of surface vibrations (bosons)and their coupling with single particles (fermions). Theanalysis and interpretation of these reactions can be quitecomplex because information about correlations is oftenhidden in the inclusive character of the extracted crosssections.

The recent revival of transfer reaction studies greatlybenefited from the construction of the new generationlarge solid angle spectrometers based on trajectory recon-struction that reached an unprecedented efficiency andselectivity [2]. The coupling of these spectrometers withlarge γ arrays allowed the identification of individual ex-cited states and their population pattern.

Grazing collisions produce a wealth of nuclei in a wideenergy and angular range and with cross sections span-ning several orders of magnitude. Total angle and energyintegrated cross sections for multi-neutron and multi-proton channels have been investigated with spectrom-eters in various systems close to the Coulomb barrier.In these systems one finds that most nuclei produced intransfer reactions have N/Z ratio smaller than one of thecompound nucleus, implying the dominance of a directmechanism in the population of different fragments. Oneof the major achievements of the last years was the ex-traction of absolute differential cross sections via a carefulstudy the response function of the spectrometer [3]. Thiswas of crucial value in the extraction of the pair-transferstrengths [4, 5].

As the multinucleon transfer reactions produce moder-ately neutron-rich nuclei with yields sufficient for studiesvia fragment-γ coincidences, this method has been usedto identify nuclei with good mass and charge resolutionand to uniquely attribute the characteristic γ rays. It isvery important to understand the structure of the statesdominantly populated by the transfer mechanism, as thefinal reaction products reflects a strong interplay betweensingle-particle and collective degrees of freedom and thereaction dynamics. Similar effects are expected to be im-portant also for very neutron-rich nuclei and the researchusing radioactive beams as a probe.

The coupling of single-particle degrees of freedom tonuclear vibration quanta is essential for the descriptionof many basic states in the vicinity of closed shells.The structure and the population pattern of the excitedstates allow to study to which extend the effects of theboson-fermion coupling are present, for example, in iso-topic chains reached via multiple-particle transfer mech-anism. The significant population of states that matcha stretched configuration of the valence neutron coupledto the vibration quanta, observed in several studied sys-tems so far, demonstrates the importance of the excita-tion of the states whose structure can be explained withthe same degrees of freedom which are essential in thereaction model: surface vibrations, and single particles.In fact, it is through the excitation of these modes thatenergy and angular momentum are transferred from therelative motion to these intrinsic degrees of freedom andthat mass and charge are exchanged among the two part-ners of the collision.

In this work selected results obtained by usingPrisma spectrometer [5, 6], alone or coupled to theClara/AGATA γ array will be presented, with specialemphasis on the major achievements of the last years.

[1] L. Corradi, G. Pollarolo, and S. Szilner, J. of Phys. G 36,113101 (2009).

[2] S. Szilner et al., Phys. Rev. C 74, 024604 (2007).[3] D. Montanari et al., Eur. Phys. J. A 47, 4 (2011).

[4] L. Corradi et al., Phys. Rev. C 84, 034603 (2011).[5] S. Szilner et al., Phys. Rev. C 84, 014325 (2011).[6] S. Szilner et al., Phys. Rev. C 87, 054322 (2013).

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FUSION14

Statistical model calculations of pre-scission neutron multiplicity for the heavy ioninduced fusion-fission reactions with actinide target 232Th

Meenu Thakur,1, ∗ B.R. Behera,1 Maninder Kaur,1 Santanu Pal,2 P. Sugathan,3 and Akhil Jhingan3

1Department of Physics, Panjab University, Chandigarh 160014, India.2CS - 6/1, Golf Green, Kolkata 700095, India (Formerly with VECC, Kolkata).

3Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.

Experimental efforts to produce the super-heavy nucleifollowed the predictions of an island of super-heavy nucleiwith enhanced stability due to shell effects [1]. Such ex-periments are extremely challenging as the formation ofheavy and super-heavy evaporation residues (ERs) aresuppressed not only by equilibrium fission, but also byquasi-fission. The main objective in the super-heavy ele-ment production is to identify those variables that hindercompound nucleus (CN) formation. This problem canbe better addressed by measuring the characteristics ofthe quasi-fission events. Properties of the entrance chan-nel, in particular the entrance channel mass-asymmetryand the deformation of colliding nuclei, play a major rolein the reaction dynamics of quasi-fission process. Withthese motivations, we have planned to study the reactionmechanism of 19F+232Th and 28Si+232Th systems popu-lating near super-heavy CN 251Es and 260Rf respectivelyusing neutron multiplicity as a probe. In the presentwork, we are reporting the calculated dissipation strengthfor the 19F+232Th system by reproducing the experimen-tal data of pre-scission neutron multiplicity available inthe literature [2] by a statistical model code [3] in theexcitation energy range of 54-90 MeV. Along with thiswe are also presenting the exploratory statistical modelcalculation of pre-scission neutron multiplicity for the28Si+232Th system in the same excitation energy range.Since no experimental data exists for pre-scission neutronmultiplicity for 28Si+232Th system in a wider excitationenergy range, we have planned to carry out this experi-ment in near future. For these calculations, we have usedfusion spin distribution from Frobrich systematics [4].

FIG. 1: Pre-Scission neutron multiplicities calculated usingBW width and Kramers’ width for the 19F+232Th system.

The calculated excitation function of pre-scission neu-tron multiplicity for 19F+232Th system using both BohrWheeler (BW) and Kramers’ width for different valuesof dissipation strength β is shown in Fig. 1 which showsthat the BW fission width severely underestimates theexperimental multiplicities. So, value of β is increased tofit the experimental data. The fitted value of β increaseswith the excitation energy as shown in Fig. 2 and thehatched area represents the uncertainity in value of βarises due to the experimental error bars. Fig. 3 in-

FIG. 2: The uncertainty in β for 19F+232Th system. The solidline indicates the best fit β values obtained at each excitationenergy.

FIG. 3: Pre-Scission neutron multiplicities calculated usingBW width and Kramers’ width for the 28Si+232Th system.

dicates only the exploratory calculations of pre-scissionneutron multiplicity for 28Si+232Th system. They pro-vide us an estimate of pre-scission neutron multiplicitieswhich one might expect from the experimental results.We observe that the pre-scission neutron multiplicity re-duces with increase in projectile mass as we go from 19Fto 28Si. This evidently reflects the effect of lowering of fis-sion barrier at higher compound nuclear spin populatedby heavier projectiles. The experimental multiplicitiesmay however be still smaller for heavier projectiles dueto quasi-fission. We aim to investigate these features inour planned experiments in near future.

∗corresponding author: [email protected]

[1] P. Armbruster, C. R. Phys. 4, 571 (2003).[2] J. O. Newton et al., Nucl. Phys. A 483, 126 (1988).[3] Jhilam Sadukhan and Santanu Pal, Phys. Rev. C 78,

011603 (R) (2008), Phys. Rev. C 79, 019901(E) (2009).[4] P. Frobrich and I.I. Gontchar, Phys. Rep. 292, 13 (1998).

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FUSION14

Comparison of quasifission mass angle distributions from experiment and TDHFcalculations

A. Wakhle,1, ∗ D. J. Hinde, C. Simenel, M. Dasgupta, and D. H. Luong1Department of Nuclear Physics, RSPE, Australian National University, Canberra, ACT 0200, Australia

Super-heavy elements [1] can only be formed by fus-ing two massive nuclei. These elements are predictedto be stabilised by nuclear shell effects associated withnear-spherical shapes around new predicted neutron andproton magic numbers. Their cross section of formationis inhibited by several orders of magnitude by the prema-ture breakup of the elongated di-nuclear system knownas quasi-fission [2, 3]; and by fission of the unstable com-pound nucleus after fusion.

FIG. 1: Time evolution of the TDHF density distribution for40Ca + 238U at E = 186.6 MeV and L = 40 ~. The snapshotscorrespond to t = 0, 0.8, 4.3 and 9.4 zs respectively.

The role of the variables influencing fusion and itscomplementary competitor quasi-fission are being inves-tigated at the ANU [4, 5] through the measurement of themass-angle distributions of the fission fragments and viathe Time Dependent Hartree Fock (TDHF) model, us-ing the TDHF3D code [6]. The mass-angle distributiontechnique used is sensitive to reactions on timescales of<10−20s. Comprehensive measurements have been madefor reactions of 40Ca, 34S, 28,30Si, 24Mg, 18O and 12Cbeams with targets of 238U, 232Th and 208Pb. Differ-ent projectile and target combinations were used suchthat the same compound nucleus was formed via tworeactions; at bombarding energies around the Coulombbarrier.

I will focus on the 40Ca + 238U reaction which wasstudied experimentally using the Mass-Angle Distribu-tions (MAD) technique and with the TDHF3D code.This is the first time that the TDHF approach has beenused to extensively study quasifission. An example of theTDHF density evolution exhibiting quasifission is shownin figure 1. The relative orientation of the heavy de-formed prolate 238U nucleus plays a major role in thereaction outcome. Collisions where the axis of defor-mation is aligned parallel with the collision axis (axialcase) lead to quasifission and short contact times of 5-10

zs, whilst anti-aligned collisions (equatorial case) lead tolonger contact times (> 23 zs). The influence of shelleffects around 208Pb in the calculated quasifission char-acteristics was confirmed by an analysis of the neutron

FIG. 2: Comparison of TDHF and experimental MAD for40Ca + 238U. The elliptical points indicate the mass and angleobtained for each TDHF calculation for a given L value.

and proton numbers of the outgoing fragments. All ofthe TDHF predictions are in agreement with experimen-tal MADs.

A subset of these results is shown in figure 2. TheMAD corresponds to the lowest measured energy thatwas also studied in detail with TDHF. The points indi-cate the mass ratio and centre of mass angle obtainedfor each L value. The initial orientation correspond tothe axial configuration. The points are labelled with thecorresponding initial orbital angular momentum. TheTDHF results follow the same trend as the experimentaldata. A similar quality of agreement is seen at higherenergies.∗corresponding author: [email protected]

[1] Yu. Ts. Oganessian et al., Phys. Rev. C 74, 044602 (2006).[2] B. B. Back et al., Phys. Rev. C 32, 195 (1985).[3] J. Toke et al., Nucl. Phys. A440, 327 (1985).[4] D. J. Hinde et al., Phys. Rev. C 53, 1290 (1996).

[5] D. J. Hinde et al., Phys. Rev. Lett. 101, 092710 (2008).[6] C. Simenel et al., Eur. Phys. J. 17, 09002, (2011).

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FUSION14

Fusion and quasi-fission in heavy systems with the microscopic time-dependent energydensity functional theory

Kouhei Washiyama1, ∗1RIKEN Nishina Center, Wako 351-0198, Japan

The interplay between nuclear structure and dynami-cal effects is crucial to properly describing heavy-ion fu-sion reactions at energies close to the Coulomb barrier.Coupled-channels calculations have been widely used todescribe the entrance channel of fusion reactions [1].

In heavy-ion fusion reactions of heavy systems, wherethe product of their charges is larger than 1600 ∼ 1800,it was observed that fusion probability of those systemsis strongly hindered around the Coulomb barrier energycompared with that of light and medium systems andwith a potential model [2]. This is called fusion hindranceand the extra energy to be needed to make such systemsto fuse is called extra push energy [3]. To understand thisphenomenon and to obtain a better description of fusionreactions of heavy systems, a dynamical model based ona Langevin equation has been developed [4]. Works withthis model have shown that the quasi-fission process iscrucial for fusion reactions in such systems.

Also, microscopic time-dependent energy density func-tional theory (historically called time-dependent Hartree-Fock, TDHF [5–7]) has been used for the analysis of fu-sion reactions in heavy systems and such extra push en-ergy is obtained from TDHF simulations [8–10].

It is well known that TDHF based on the Skyrme en-ergy density functional provides a unique tool for describ-ing nuclear structure and nuclear reactions over the wholenuclear chart in a unified self-consistent framework. Re-cently, we have proposed a method to directly extractnucleus-nucleus potential and one-body energy dissipa-tion from the relative motion to nuclear intrinsic excita-tions of colliding nuclei from TDHF simulations [11, 12].We have shown that nucleus-nucleus potentials obtainedwith this method are in good agreement with experimen-tal data and show energy dependence. This energy de-pendence is due to the effect of dynamical reorganizationof the density of colliding nuclei. The property of theenergy dissipation is also analyzed [12].

In this contribution, we discuss the property ofnucleus-nucleus potential and energy dissipation in heavysystems obtained with the method mentioned above. Wewill report that the property of obtained potentials forheavy systems is different from that of light, medium sys-tems. We will also discuss energy dissipation for heavysystems and analyze the property of fusion hindrance indetail.

∗corresponding author: [email protected]

[1] For a recent review, K. Hagino and N. Takigawa, Prog.Theor. Phys. 128, 1061 (2012).

[2] C.-C. Sahm et al., Nucl. Phys. A 441, 316 (1985).[3] W. J. Swiatecki, Phys. Scripta 24, 113 (1981); Nucl.

Phys. A 376, 275 (1982).[4] For example, Y. Aritomo, K. Hagino, K. Nishio, and S.

Chiba, Phys. Rev. C 85, 044614 (2012).[5] P. Bonche, S. E. Koonin, and J. W. Negele, Phys. Rev.

C 13, 1226 (1976).[6] H. Flocard, S. E. Koonin, and M. S. Weiss, Phys. Rev.

C 17, 1682 (1978).

[7] J. W. Negele, Rev. Mod. Phys. 54, 913 (1982).[8] C. Simenel, B. Avez, C. Golabek, Proceeding of the

KERNZ08 conference, arXiv:0904.2653.[9] L. Guo and T. Nakatsukasa, EPJ Web Conf. 38, 09003

(2012).[10] C. Simenel, Eur. Phys. J. A 48, 152 (2012).[11] K. Washiyama and D. Lacroix, Phys. Rev. C 78, 024610

(2008).[12] K. Washiyama, D. Lacroix and S. Ayik, Phys. Rev. C

79, 024609 (2009).

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FUSION14

Study of multinucleon transfer reactions of 136Xe + 198Ptfor production of exotic nuclei

Y.X. Watanabe,1, ∗ Y. Hirayama,1 N. Imai,1 H. Ishiyama,1 S.C. Jeong,1 H. Miyatake,1 M. Oyaizu,1 S. Kimura,2

M. Mukai,2 S.H. Choi,3 Y.H. Kim,3 J.S. Song,3 E. Clement,4 G. de France,4 A. Navin,4 M. Rejmund,4 C. Schmitt,4

G. Pollarolo,5 L. Corradi,6 E. Fioretto,6 D. Montanari,7, † M. Niikura,8, ‡ D. Suzuki,8 H. Nishibata,9 and J. Takatsu9

1High Energy Accelerator Research Organization (KEK), Ibaraki, Japan2University of Tsukuba, Ibaraki, Japan

3Seoul National University, Seoul, Korea4Grand Accelerateur National d’Ions Lourds (GANIL), Caen, France

5Universita di Torino and INFN, Torino, Italy6INFN, Laboratori Nazionali di Legnaro (LNL), Padova, Italy

7Universita di Padova, Padova, Italy8Institut de Physique Nucleaire (IPN), Orsay, France

9Osaka University, Osaka, Japan

Multinucleon transfer (MNT) reaction between twoheavy ions at energies around the Coulomb barrier isconsidered as a promising candidate to produce and in-vestigate exotic nuclei [1–3]. Especially in the region ofneutron-rich nuclei around the neutron magic number of126, which is difficult to access by other production meth-ods, the MNT reaction is expected to provide a meansto efficiently produce them. The nuclear region has beenattracting an astrophysical interest because the waitingpoint nuclei on the r-process path, which are progeni-tors of the peak at the mass number of 195 in the solarr-abundance distribution, are located there.

We have been developing a gas-catcher type laser ionsource named KEK Isotope Separation System (KISS),which in now on commissioning, to produce, separateand measure the nuclear properties of the neutron-richnuclei around the neutron magic number of 126, whichare produced by the MNT reaction [4, 5]. We adopted thereaction system of 136Xe and 198Pt, which is consideredto be one of the best candidates to efficiently produce thenuclei of interest, because the neutron stripping (fromprojectile to target) and the proton pickup (from targetto projectile) would occur comparatively easily owing tothe ratio of neutron numbers to proton numbers for theprojectile 136Xe, 1.52, comparative to the ratio for thetarget 198Pt, 1.54.

To investigate the feasibility of the nuclear productionof the system, we have studied the collisions between136Xe and 198Pt at the laboratory energy of 8 MeV/A,

which is 55% above the Coulomb barrier. The mea-surement was performed at GANIL. The 198Pt targetwas irradiated by the 136Xe beam, and the projectile-like fragments (PLFs) were detected by the large ac-ceptance magnetic spectrometer VAMOS++ [6]. Thegamma-rays from the PLFs and target-like fragments arealso detected by the high efficiency gamma detector ar-ray EXOGAM [7] surrounding the target. Fig. 1 showsthe distribution of the PLFs detected by VAMOS++.

In this presentation, we will introduce the KISSproject, and report on the measurements of the MNTreactions of 136Xe + 198Pt.

FIG. 1: Distribution of the projectile-like fragments in thereaction of 136Xe + 198Pt detected by VAMOS++.

∗corresponding author: [email protected]†Present address:Universita degli Studi di Milano and INFN, Mi-lano, Italy

‡Present address:University of Tokyo, Tokyo, Japan

[1] C.H. Dasso, G. Pollarolo and A. Winther, Phys. Rev. Lett.73, 1907 (1994).

[2] V. Zagrebaev and W. Greiner, Phys. Rev. Lett. 101,122701 (2008).

[3] L. Corradi, G. Pollarolo and S. Szilner, J. Phys. G 36,113101 (2009).

[4] S.C. Jeong et al., KEK Report 2010-2 (2010).

[5] Y. Hirayama et al., Nucl. Instrum. Methods Phys. Res. B317, 480 (2013).

[6] M. Rejmund et al., Nucl. Instrum. Methods Phys. Res. A646, 184 (2011).

[7] J. Simpson et al., Heavy Ion Phys. 11, 159 (2000).

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FUSION14

The evolution of signatures of quasifission in reactions forming Curium

E. Williams,1 D. J. Hinde,1 M. Dasgupta,1 R. du Rietz,1, ∗ I. P. Carter,1 M. Evers,1

D. H. Luong,1 S. D. McNeil,1 D. C. Rafferty,1 K. Ramachandran,1, † and A. Wakhle1

1Department of Nuclear Physics, Research School of Physical Sciences and Engineering,The Australian National University, Canberra, ACT 0200, Australia

Quasifission, a fission-like reaction outcome in whichno compound nucleus forms, is an important competitorto fusion in reactions used for super-heavy element for-mation. The precise mechanisms driving the competitionbetween quasifission and fusion are poorly understood.

To explore the influence reaction parameters have onquasifission probabilities, an investigation into the evo-lution of quasifission signatures as a function of en-trance channel parameters is required. Using the Aus-tralian National University’s 14UD tandem acceleratorand CUBE detector for two-body fission studies, mea-surements were made for a diverse range of reactions

forming isotopes of Curium. Observables known to revealsigns of quasifission—namely mass ratio spectra, mass-angle distributions, and angular anisotropies—were ex-tracted [1].

As this work will show, evidence of quasifission was ob-served in all reactions—even for those using the lightestprojectile (12C + 232Th). But the observables showingevidence of quasifission were not the same for all reac-tions. In this presentation, the evolution of quasifissionsignatures as a function of reaction entrance channel pa-rameters will be demonstrated, and a link between thisevolution and reaction timescales will be presented.

∗Current address: Malmo University, Malmo 205 06, Sweden†Permanent address: Nuclear Physics Division, Bhabha Atomic

Research Centre, Mumbai 400085, India

[1] E. Williams et al., Phys. Rev. C 88, 034611 (2013).

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FUSION14

An alternative explanation of heavy ions sub-barrier fusion enhancement

R. Wolski1, 2, ∗1Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna, Russia

2Henryk Niewodniczanski Institute of Nuclear Physics PAS, Krakow, Poland

Fusion of two atomic nuclei happens if interacting bod-ies can overcome somehow the barrier formed by the nu-clear, Coulomb and centrifugal potentials. It has beenbelieved that for the c.m. energy below the barrierheight, classically forbidden fusion occurs as an instanta-neous act of barrier quantum tunneling. The tunnelingprobability depends on the barrier parameters. There-fore, one could expect, that for pairs of heavy ions havingalmost the same barrier, their fusion likelihood shouldbe very close. However, relevant sub-barrier fusion ex-perimental data demonstrate very often huge differences.This effect is know as sub-barrier fusion enhancement andis hitherto explained as being originated by the intrinsicproperties of individual nuclei, their susceptibility to col-lective excitations, and nucleon or cluster transfers. Suchdirect reactions modify the barrier through a coupling re-action mechanism and lead either to fusion enhancementor to the hindrance of fusion, depending on a referencelevel.

We would like to show that the opportunity for the sub-barrier fusion is determined by the phase-space availablein this process, what is the trait for the compound nu-cleus mechanism. Its probability is governed mainly bygeneral properties of the participating nuclei.

In order to compare fusion data for various systems asimple empirical energy scaling has been introduced. Anoutcome of a suggested data reduction is presented inFig. 1 where shown are the experimental data for 12 sys-tems of similar masses adjusted by means of the proposedscaling. One could see, in Fig. 1, initial fusion enhance-ment is greatly reduced, in some cases by two orders ofmagnitudes.

An effectiveness of the data reduction procedure forsub-barrier fusion enhancement suggests that the Com-pound Nucleus mechanism in heavy ions fusion, deeplyunder the barrier, could not be ignored. This impliesthat the discussed process is a slow one. That conclusionis consistent with estimations of the heavy ions underbarrier relative velocity, which is much smaller than theaverage nucleon velocity inherent to a nucleus. It meansthat during the contact time between two nuclei, there isenough chance for interaction between their nucleons.

There are several advantages of the proposed treat-ment of the sub-barrier fusion phenomena. It could ex-plain a bad behavior of the low energy asymptotics inthe barrier penetration models. It has a straightforward

implication for estimations of fusion yield for uninvesti-gated systems. The sub-barrier fusion cross-section for apair of nuclei could be predicted easily, without involvingany structural effects of the colliding nuclei, if the cross-section data measured for a similar system are known.

FIG. 1: Fusion cross-section for 12 nuclear systems in termsof reduced energy parameter.

We believe our empirical rule is a general one. It shouldbe applicable also for fusion study of weakly bound exoticradioactive nuclei. This subject is much discussed cur-rently. It has been pointed out that the weak boundingof these nuclei makes fusion easier due to the presenceof the breakup and transfer channels. We can predict astrongly enhanced fusion for 3He, as well as for 6He nu-clei, respect to the alpha particle fusion. A weak bound-ing of 3He, unlike that of 6He, is out of question. How-ever, a common feature for these two projectiles is thepresence of highly energetic transfer channels: (3He,4He)and (6He,4He) in the nuclear interaction of 3He and 6Herespectively. Therefore, it would be interesting to con-front sub-barrier fusion data for 3He and 6He on the sametargets.

Limitations of a proposed approach, some of its predic-tions and suggestions for experimental verifications willbe discussed.∗[email protected]

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FUSION14

Low energy in-complete fusion and its relevance to synthesis of superheavy elements

Abhishek Yadav,1, ∗ Vijay R. Sharma,1 Pushpendra. P. Singh,2 D. P. Singh,1 Indu Bala,3 R. Kumar,3

M. K. Sharma,4 Sunita Gupta,5 S. Muralithar,3 R. P. Singh,3 B. P. Singh,1 and R. Prasad1

1Department of Physics, Aligarh Muslim University, Aligarh (U.P.)-202002, India2GSI Helmholtz Centre for Heavy Ion Research GmbH, D-64291 Darmstadt, Germany

3NP-Group: Inter University Accelerator Centre, New Delhi-110067, India4Physics Department, S. V. College, Aligarh (U.P.), India5Physics Department, Agra College, Agra (U.P.), India

Considerable efforts are being employed to synthesizesuperheavy elements using heavy-ion induced completefusion (CF) reactions [1]. In addition to the fission andquasi-fission, the existence of incomplete fusion (ICF) atlow incident energies (i.e., ≈ 4-7 MeV/nucleon) may addcomplexity to the synthesis of superheavy elements. Ingeneral, at these energies, CF is supposed to be the solecontributor to the total fusion cross section. However,in recent years a large fraction of ICF has been observedat energies as low as ≈ 4-7 MeV/nucleon. The onsetof ICF at near barrier energies triggered the resurgentinterest to understand the ICF reaction dynamics. InICF reactions the incident projectile is breaks up into itsfragments, as a consequence of excess input angular mo-mentum, and one of the breakup fragments fuses with thetarget nucleus[2—6]. The onset of ICF at slightly abovebarrier energies has been emphasized in the excitationfunction (EFs) measurements [5], however, a clear exis-tence of ICF at low incident energies has been demon-strated by measuring more than one linear momentumtransfer components in the forward recoil ranges [4]. Inaddition to this, the unclear or ambiguous dependencesof ICF on various entrance channel parameters have alsobeen explored and contradicting dependences of the frac-tion of incomplete fusion have been reported [2, 6]. Mor-genstern et al. [7] correlated the ICF fraction with en-trance channel mass asymmetry (µA). Recently, Singh etal. [3] introduced the importance of projectile structurein ProMass-systematics.

Hence, in order to explore the above aspects and to finda consistent general systematics for low energy ICF reac-tions, which may support the formation of super-heavyformation physics, several experiments have been per-formed [3—6]. In one of our recent papers, the measure-ment of EFs for 12,13C+159Tb systems have been pre-sented, where significant contribution of ICF reactionshave been observed [4, 5]. Here, the break-up probabil-ity for 13C projectile is found to be noticeably smallerthan for 12C projectile, which has been explained on the

basis of the proposed ‘alpha-Q-value systematics’. In or-der to strengthen the proposed systematics and to lookfor the projectile structure effect on ICF reactions, theexperiments the EFs of radio-nuclides populated duringthe interactions of 18O+159Tb at energies ≈ 4-7 MeV/Ahave been carried out. The present data will be com-pared with 16O+159Tb data, to draw conclusions aboutalpha-Q-value systematics, as 18O-beam has more neg-ative Qα-value than 16O. In these experiments the tar-gets of 159Tb of thickness ≈ 1.5 - 2.0 mg/cm2 and Al-catchers (≈1.5-2.5 mg/cm2) were used. Several stacks oftarget-catcher assembly (targets followed by Al-catcherfoils ) have been irradiated to cover a wide energy range≈70-100 MeV. The activities induced in the samples wererecorded by counting each target alongwith the catcherfoil, using a pre-calibrated HPGe γ-ray spectrometer ofresolution 2keV for 1332 keV γ-ray of 60Co source. TheEFs of identified residues have been measued and ana-lyzed within the framework of the statistical model codePACE4. The code PACE4 takes formation and decay ofCF events into account according to the Hauser-Feshbachtheory of CN decay, therefore, any deviation in the ex-perimental EFs from the PACE4 calculations may be at-tributed due to the ICF processes. The EFs for xn andpxn channels are found to be satisfactorily reproducedby theoretical predictions, indicating their population viaCF process only. Further, the experimentally measuredEFs for αxn-channels show significant enhancements overthe calculated values, which may be attributed as thecontribution due to ICF-processes. It may, however, bepointed out that the CN in the present work is not veryheavy. A rich data set from medium to heavy targetsmay help to develop some systematics to understand theprobability of involved reaction processes at these ener-gies, which may be useful in the super heavy elementresearch. Further, details regarding the effect of projec-tile structure and α-Q-value on the ICF strength functionand comparison of 18O+159Tb with available 16O+159Tbdata will be presented.

∗corresponding author: [email protected]

[1] V. I. Zagrebaev, Nucl. Phys. A 734 164 (2004) and refer-ences therein.

[2] M. DasGupta et al., Phys. Rev. C 66, 041602(R) (2002).[3] P. P. Singh et al., Phys. Rev. C 77, 014607 (2008).

[4] Abhishek Yadav et al., Phys. Rev. C 85, 064617 (2012).[5] Abhishek Yadav et al., Phys. Rev. C 85, 034614 (2012).[6] Abhishek Yadav et al., Phys. Rev. C 86, 014603 (2012).[7] H. Morgenstern et al., Phys. Rev. Lett. 52, 1104 (1984).

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FUSION14

First experimental tests of the kinematic separator SHELS(Separator for Heavy ELement Spectroscopy)

A. Yeremin,1, ∗ O. Malyshev,1 A. Popeko,1 V. Chepigin,1 A. Svirikhin,1

A. Lopez-Martens,2 K. Hauschild,2 O. Dorvaux,3 B. Gall,3 and J. Gehlot41FLNR JINR, Dubna, Russia

2CSNSM, Orsay, France3IPHC, Strasbourg, France4IUAC, New Dehli, India

In the past, various types of reactions and identifica-tion techniques were applied in the investigation of for-mation cross sections and decay properties of transura-nium elements. The fusion - evaporation reactions withheavy targets, recoil - separation techniques and identi-fication of nuclei by the parent – daughter generic co-incidences with the known daughter-nuclei after implan-tation into position - sensitive detectors were the mostsuccessful tools for production and identification of theheaviest elements known presently. This technique maybe further improved and presently it may be very promis-ing for the identification of new elements, search for newisotopes and measurement of new decay data for theknown nuclei. Within the past 15 years, the recoil sep-arator VASSILISSA [1] has been used for the investiga-tions of evaporation residues (ERs) produced in heavyion induced complete fusion reactions. In the course ofthe experimental work a bulk of data on ERs formationcross sections, synthesized in asymmetric reactions wascollected. With γ and β detector arrays, installed atthe focal plane of the VASSILISSA separator, detailedspectroscopy of Fm - Lr isotopes was performed dur-ing last 5 years. In the years 2004 - 2010 using theGABRIELA (Gamma Alpha Beta Recoil Invetsigationswith the ELectromagnetic Analyser) set–up [2] the exper-iments aimed to the gamma and electron spectroscopyof the transfermium isotopes, formed at the completefusion reactions with accelerated heavy ions were per-formed. Isotopes of No and Lr were studied. The exper-iments with high intensity 22Ne beam showed, that forslow evaporation residues rather high (∼ 10 % transmis-sion efficiency need to be obtained. In this case for α−γand α− β coincidences used in the study of the isotopesof 104 and 105 elements good statistics could be obtainedduring one month of the experiment. Accumulated expe-rience allowed us to perform ion optical calculations and

to design the new experimental set up, which will collectthe base and best parameters of the existing separatorsand complex detector systems used at the focal planes ofthese installations [3]. New experimental set up (SHELS,the velocity filter) on the basis of existing VASSILISSAseparator was developed for synthesis and studies of thedecay properties of heavy nuclei (see Fig. 1). In May -July 2013 first test experiments were performed. At thefocal plane of the separator GABRIELA set up (α, β, γdetectors array) was installed. Beam of 22Ne from U400cyclotron and Au, 198Pt, 206,208Pb and ∗238U targetswere used in test experiments. For evaporation residuesfrom reactions with Au and 198Pt targets transmissionefficiency about 5 % was obtained.

FIG. 1: Schematic view of the SHELS separator.

In November 2013 test experiments with accelerated50Ti were performed. With 164Dy and 208Pb targetstransmission efficiency for evaporation residues and sup-pression factors for scattered Ti beam were studied.∗corresponding author: [email protected]; Permanent address:FLNR

JINR, Joliot Curie str. 6, 141980 Dubna, Moscow region, Russia

[1] A. Yeremin et. al., Phys. At. Nucl., 66, 1042 (2003).[2] K. Hauschild et. al., Nucl. Instr. and Meth., A560 388

(2006).

[3] A. Yeremin et. al., Nucl. Instr. and Meth., B266 4137(2008).

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FUSION14

Synthesis of superheavy nuclei: nearest and distant opportunities

V.I. Zagrebaev1, ∗1Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Moscow Region, Russia

There are only 3 methods for the production of heavyand superheavy (SH) nuclei, namely, fusion of stable andradioactive nuclei, a sequence of neutron capture andbeta(-) decay, and multinucleon transfer reactions. Allof them will be discussed in the talk. The extension ofthe area of known isotopes of SH elements is extremelyimportant for further developing the models which willbe able to predict well the properties of SH nuclei lo-cated beyond this area (including those at the island ofstability). Low values of the fusion cross sections andvery short half-lives of nuclei with Z>120 put obstaclesin synthesis of new elements. At the same time, an impor-tant area of SH isotopes located between those producedin the cold and hot fusion reactions remains unstudiedyet. This gap could be filled in ordinary fusion reactionsof 48Ca with available lighter isotopes of Pu, Am, andCm. Experiment of such kind was started in Dubna inDecember of 2013.

FIG. 1: Possible experiments on synthesis of SH elements.

The neutron-enriched isotopes of SH elements may bealso produced with the use of a 48Ca beam if a 250Cmtarget would be prepared. In this case we get a realchance to reach the island of stability owing to a possiblebeta(+) decay of 291114 nucleus formed in the 3n evap-oration channel of this reaction with a cross section ofabout 0.8 pb [1] (see Fig. 2).

Renewed interest in the multinucleon transfer reactionswith heavy ions is caused by the limitations of other reac-tion mechanisms for the production of new heavy and SHneutron enriched nuclei. Multinucleon transfer process

in near barrier collisions of heavy ions seems to be quitepromising reaction mechanism allowing one to produce

FIG. 2: Pathway to the middle of the island of stability.

FIG. 3: Production new neutron enriched isotopes of trans-fermium elements in collisions of 238U with 248Cm target.

and explore neutron-rich heavy nuclei including those lo-cated at the SH island of stability [2]. Our predictionsfor the production of new neutron-rich heavy nuclei inmultinucleon transfer reactions will be discussed and newexperiments will be proposed. A special attention will bepaid to the shell effects in damped collisions of heavy ionsand to the “inverse” quasi-fission mechanism leading tothe formation of reaction fragments with masses lighterthan projectile and heavier than target masses.∗corresponding author: [email protected]

[1] V.I. Zagrebaev, A.V. Karpov and W. Greiner, Phys. Rev.C 85, 014608 (2012).

[2] V.I. Zagrebaev and W. Greiner, Phys. Rev. C 87, 034608(2013).

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FUSION14

GALS - setup for production and study of heavy neutron rich nuclei

S. Zemlyanoy,1, ∗ V. Zagrebaev,1 E. Kozulin,1 Yu Kudryavtsev,2 V. Fedosseev,3 and R. Bark4

1Joint Institute for Nuclear Research, Dubna 141980, Russia2Instituut voor Kern- en Stralingsfysica, Leuven, Belgium

3CERN, Switzerland4iThemba LABS, Nat. Research Foundation, South Africa

Unexplored area of heavy neutron rich nuclei is veryimportant for nuclear physics investigations and, in par-ticular, for the understanding of astrophysical nucleosyn-thesis. In this region is the closed neutron shell N=126located which is the last ”waiting point” in the r-process.The half-lives and other characteristics of these nucleiare extremely important for this process and scenario ofsupernovae explosions. Study of the structural propertiesof nuclei along the neutron shell N = 126 could also con-tribute to the present discussion of the quenching of shellgaps in nuclei with large neutron excess. During the lastseveral years a combined method of separation has beenintensively studied and developed based on stopping nu-clei in gas and subsequent resonance laser ionization of

them. This method was used up to now for separationand study of light exotic nuclei and fission fragments.Such techniques allows one to extract nuclei with a givenatomic number, while a separation of the single ionizedisotopes over their masses can be done rather easily bya magnetic field. A new setup, based on these principlesand devoted to synthesis and study of new heavy nucleiformed in low energy multi-nucleon transfer reactions isunder stage of realization at Flerov lab. JINR. A cre-ation and a launch of this facility will open a new field ofresearch in low-energy heavy-ion physics, and new hori-zons in the study of unexplored ”north-east” area of thenuclear map.

∗corresponding author: [email protected]

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FUSION14

Langevin dynamics in nuclear fusion emerging from quantum molecular dynamicssimulations

Kai Wen,1 Fumihiko Sakata,2, 1 Zhu-Xia Li,3 Xi-Zhen Wu,3 Ying-Xun Zhang,3 and Shan-Gui Zhou1, 4, ∗1State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,

Chinese Academy of Sciences, Beijing 100190, China2Institute of Applied Beam Science, Graduate School of Science and Technology, Ibaraki University, Mito 310-8512, Japan

3China Institute of Atomic Energy, Beijing 102413, China4Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000, China

(Dated: February 13, 2014)

The fusion of two nuclei is one of the major non-equilibrium processes in low energy nuclear reactionswhere the fluctuation and dissipation play importantroles. Under various assumptions, many macroscopictransport models have been introduced to evaluate theformation of a compound nucleus in heavy-ion fusion re-actions However, the microscopic mechanism on how twocolliding nuclei fuse, especially how the relevant kineticenergy dissipates into the intrinsic degrees of freedom(DoF), remains a subject requiring further research.

It is becoming feasible to get various information outof microscopic numerical simulations. The quantummolecular dynamics (QMD) model is a microscopic dy-namical n-body theory which was successfully used inintermediate-energy heavy-ion collisions (HIC) [1]. Animproved QMD (ImQMD) model has been developed inorder to extend the application of QMD to low-energyHICs near the Coulomb barrier [2]Making full use ofthe microscopic information provided by ImQMD simu-lations, we have tried to understand how the macroscopicfusion dynamics emerges out of the microscopic one [3].

Ten thousand simulations were made for head-on col-lisions of 90Zr+90Zr with an incident energy E = 195MeV. In such symmetric reactions, the whole system canbe divided into the left- and right-half parts. The ran-dom force or the fluctuation of force in the ith event isdefined as

δF (R)i ≡ Fi(R)− 〈F (R)〉, (1)

where Fi ≡∑A

j=1 fji denotes the total force acting on

the left (right) part of the system in the ith event,〈F 〉 ≡ 1

n

∑ni=1 Fi the mean value, and f j

i the force onthe jth nucleon in the left (right) part. It was foundthe dissipation dynamics of the relative motion betweentwo fusing nuclei is caused by a non-Gaussian distribu-tion of the random force (see Fig. 1 for details). Thefriction coefficient as well as the time correlation func-

tion of the random force takes particularly large valuesin a region a little bit inside of the Coulomb barrier.A clear non-Markovian effect was also observed in thetime correlation function of the random force. It hasbeen further shown that, when the incident energy is rel-atively low, an emergent dynamics of the fusion processcan be described by the generalized Langevin equationwith memory effects by appropriately incorporating themicroscopic information of individual nucleons throughthe random force and its time correlation function.

0 4 8 12 160.0

0.2

0.4

0.6

0.8

-10 0 10

-5

0

5

Forc

e (M

eV/fm

)z (fm)

-5

0

5

-10 0 10

Forc

e (M

eV/fm

)z (fm)

Prob

abili

ty d

istri

butio

n

Random force (MeV/fm)

R = 13.5 fm(a)

(b)

FIG. 1: Distribution of the random force δF (R) atR = 13.5 fm which is divided into the symmetric Gaussian(dark blue) and asymmetric tail (light blue) parts. Two typ-ical events are shown in the inset: The abscissa and the ordi-nate express relative position z of each nucleon and the forceit feels in the z direction. Taken from Ref. [3].

Further investigations, including the dependences ofthe effects discussed above on the incident energy, reac-tions systems, and the impact parameters will be alsopresented [4].∗Corresponding author: [email protected]

[1] J. Aichelin, Phys. Rep. 202, 233 (1991).[2] N. Wang et al., Phys. Rev. C 65, 064608 (2002); ibid, 69,

034608 (2004).[3] K. Wen, F. Sakata, Z.-X. Li, X.-Z. Wu, Y.-X. Zhang, and

S.-G. Zhou, Phys. Rev. Lett. 111, 012501 (2013).[4] K. Wen et al., in preparation.

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