!∀ ∀

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1/23

1

Oblate nuclear shapes and shape transitions

in neutron-deficient rare earth isotopes

CEA Saclay (A. Görgen, W. Korten, A. Obertelli, B. Sulignano, Ch. Theisen)

Univ. Oslo (A. Bürger, M. Guttormsen, P. Hoff, A.C. Larsen, T. Renstrøm, S. Siem)

CEA DIF (J.-P. Delaroche, M. Girod)

Univ. Köln (A. Dewald, M. Hackstein, Th. Pissulla, W. Rother)

INFN Legnaro (A. Gottardo, D. Mengoni, C. Michelagnoli, D.R. Napoli, E. Sahin,

J.J. Valiente-Dobon)

INFN Padova (S. Aydin, E. Farnea, R. Menegazzo, F. Recchia, C.A. Ur)

Abstract

We propose to investigate the evolution of nuclear shapes and shape coexistence in neutron-

deficient rare earth nuclei below the N=82 shell closure by measuring lifetimes of low-lying

excited states in 140Sm using the recoil-distance Doppler shift technique with the Cologne

Plunger device coupled to the GASP detector array. The nuclei with N≈78 and Z≥62 belong

to one of the few regions of heavy nuclei in the Segrè chart where oblate shapes are expected

near the ground state. Since different nuclear shapes are thought to coexist and change rapidly

with excitation energy, spin, proton and neutron number in this region, the measurement of

electromagnetic transition rates represents a stringent test of theoretical models and effective

nucleon-nucleon interactions. The proposed experiment is complementary to a recently started

program to study nuclear shapes in light rare earth nuclei with Coulomb excitation of

radioactive beams at the ISOLDE facility at CERN.

Introduction

The shape is one of the most fundamental properties of an atomic nucleus, along with its mass

and radius. To first order the binding energy is independent of the sign of the deformation,

and prolate and oblate shapes should be equally probable. In light nuclei prolate and oblate

shapes occur indeed more or less equally. For heavier nuclei (N,Z>50), where the shell

structure changes from a harmonic oscillator type to a Mayer-Jensen type with intruder

orbitals, a strong dominance of prolate shapes is observed, which has been related to the

strength of the spin-orbit interaction relative to the radial term in the nuclear interaction [1].

Oblate shapes are then only expected when a major shell is almost filled due to the strong

shape-driving effect of holes in the Ω=1/2 orbitals. This effect is seen for example in HFB

calculations, which predict oblate ground-state shapes to occur just below the N=82, N=126,

and Z=82 shell closures (see Fig. 1). The deeper origin of the prolate shape dominance in the

nuclear chart, however, is still subject of debate [2].

In some areas of the nuclear chart the shape is very sensitive to structural effects and can

change from one nucleus to its neighbor. In addition to shape changes with proton or neutron

number, the shape can also change with excitation energy or angular momentum within the

same nucleus. Such changes are caused by a rearrangement of the orbital configuration of the

nucleons or by the dynamic response of the nuclear system to rotation. In some cases

configurations corresponding to different shapes coexist at similar energies. The wave

functions of such states can then mix according to the laws of quantum mechanics. The

experimental measurement of observables related to the nuclear shape represents a stringent

test for theoretical models, in particular in the case of shape coexistence and shape mixing.

Apart from the fundamental question where in the nuclear chart oblate shapes can be

found, nuclei with oblate ground-state shapes are also the best candidates to study the

phenomenon of oblate-prolate shape coexistence, since prolate shapes become rapidly favored

2/23

How does the β-band of a transitional nucleus stretch with angular momentum?

An RDDS-study of Qt-values from projectile-Coulomb excitation of 158Dy with the AGATA-Demonstrator

O. Möller, M. Reese, L. Coquard, J. Leske, Th. Möller, T. Kröll, N. Pietralla

Institut für Kernphysik, TU Darmstadt, Darmstadt, Germany A.Dewald, M.Hackstein, Th. Pissulla, W. Rother

Institut für Kernphysik, Universität zu Köln, Köln, Germany and the AGATA-collaboration

Abstract The physics aim of the proposed experiment is to measure unknown level lifetimes in the β-band of the nucleus 158Dy and to re-measure lifetimes in the ground band with higher precision using the Recoil Distance Doppler Shift technique. The method of inverse or projectile Coulomb excitation in combination with the plunger technique will be of significant importance to measure lifetimes in neutron rich nuclei with radioactive ion beams. Therefore it is crucial to study this method with the new generation of germanium detectors at stable beam experiments with sufficient statistics. This will allow to study possible systematic errors, mainly caused by the deorientation effect and to develop techniques for correcting impacts originating from these effects. Furthermore it was recently shown that it is possible to derive quadrupole moments from RDDS data using the angular distributions of the γ-rays. This additional feature is planned to be adapted to the highly segmented AGATA detectors. Finally it is proposed in one additional day of beamtime to implement the real differential plunger technique. Using two thinner degrader foils instead of one, it is possible to measure simultaneously at two different target-degrader seperations. This makes it possible to measure lifetimes without changing the distance, avoiding errors due to normalization uncertainties. The capability of the AD is essential in this kind of experiments for precise Doppler correction of the γ-rays emitted at high recoil velocities. For accurate kinematic corrections the first interaction point of the gamma in the detector is needed. The high efficiency of the AD for γ-rays with energies above 1 MeV will strongly support the proposed experiment, because lifetimes in the β-band have to be deduced from interband γ-rays in this energy region. The described simple set-up of this proposed experiment makes it applicable as a first stage experiment at the AGATA demonstrator.

3/23

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4/23

42CA-COULEX

Coulomb Excitation of the Presumably Super-Deformed Band in 42

Ca

A. Maja, P. Napiorkowski

b, F. Azaiez

c, J.J. Valiente Dobon

f,

M. Kmiecika, M. Chełstowskaa, P. Bednarczyka, M. Ciemałaa, A. Czermaka, B. Dulnya, B. Fornala,

J. Grębosza, M. Matejska-Minda

a, K. Mazurek

a,p, W. Męczyński

a, S. Myalski

a, J. Styczeń

a,

M. Zięblińskia, K. Hadyńskab, E. Grodnerb, G. Jaworskib, M. Palaczb, J. Srebrnyb, K. Wrzosekb,

M. Zielińskab, I. Matea

c, Ch. Bourgeois

c, S. Franchoo

c, F. Ibrahim

c, M. Lebois

c, I. Stefan

c,

D. Verneyc, G. de Angelisf, A. Gadeaf, D. Bazzaccog, E. Farneag, G. Benzonie, A. Braccoe,

S. Brambillae, F. Camera

e, S. Leoni

e, B. Million

e, O. Wieland

e, R. Nicolini

e, D. Mengoni

e,

A. Goergend, W. Kortend, J. Gerlh, M. Górskah, H.J. Wollersheimh, Zs. Dombradii, D. Sohleri,

D. Curienj, N. Redon

k, O. Stezowski

k, Ch. Schmitt

p, D. Balabanski

l, G. Georgiev

m, E. Fiori

m,

R. Kulessan, D. Jenkinso, B. Wadswortho

and the AGATA collaboration

a The Niewodniczanski Institute of Nuclear Physics, PAN, Krakow, Poland;

b Warsaw University, Warsaw, Poland;

c IPN Orsay, France;

d CEA Saclay, France;

e Università degli Studi e INFN sez di Milano, Milano, Italy;

f INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy;

g Università di Padova e INFN, sez. di Padova, Padova, Italy;

h GSI Darmstadt, Germany;

i ATOMKI Debrecen, Hungary;

j IPHC Strasbourg, France;

k IPN Lyon, France;

l INRNE-BAS, Sofia, Bulgaria; m CSNSM, Orsay, France; n Jagellonian University, Krakow, Poland; o University of York, UK, p GANIL, Caen, France.

Spokespersons: A. Maj, P. Napiorkowski, F. Azaiez

LNL liaison: J.J. Valiente-Dobon

Abstract: We propose to use the AGATA-Demonstrator with ancillary position sensitive detector DANTE for scattered

heavy ions in order to perform Coulomb excitation of the stable 170 MeV 42Ca beam on a 208Pb target (1 mg/cm2

thick) and extract B(E2) values of transitions up to those of the rotational, presumably super-deformed, band in

this nucleus. The obtained values will be compared to those extracted from lifetime measurement. This

technique, if successful, could be than used for other nuclei with low-lying super-deformed bands, also

employing intense radioactive beams. We request 15 shifts of beam time and 3 shifts for the setting of the

experiment.

5/23

Study of Collectivity at High Spins forthe Normal-Deformed Bands in 81Sr.

A. Gottardo1,2 , J.J. Valiente-Dobon2, S. Aydin1, D. Bazzacco1,G. de Angelis2, E. Farnea1, A. Gadea3, A. Goergen4, W. Korten4, S. Lenzi1,S. Lunardi1, D. Mengoni1, R. Menegazzo1, C. Michelagnoli2, D.R. Napoli2,A. Obertelli4, F. Recchia1, E. Sahin2, B. Sulignano4, C. Theisen4, C.A. Ur1.

1Dipartimento di Fisica and INFN, Sezione di Padova, Padova, Italy.2INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy.

3Instituto de Fısica Corpuscular, Valencia, Spain.4CEA-Saclay, DAPNIA/SPhN, F-91191 Gif-sur-Yvette Cedex, France.

Spokepersons: A. Gottardo, J.J. Valiente-Dobon

Abstract

The aim of this experiment is to study shape evolution at high spins for thenormal-deformed (ND) bands in 81Sr. It is predicted that the ND bands in 81Srremain collective up to their maximal spins, not exhibiting band termination inthe usual sense. The main objective is to measure the lifetimes of the highest spinstates for the normal-deformed bands using the thin-target Doppler-shift attenua-tion method (DSAM), which will help us to elucidate the deformation changes athigh spins. In order to populate the high spins states in 81Sr, a 58Ni(28Si,4pn)81Srfusion-evaporation reaction at a beam energy of 130 MeV is proposed. The Agata-

Demonstrator array will be used to measure the γ rays emitted in the reaction.

1

6/23

Isotopic effects on the level density and symmetry energyBeam time requirement

M. D’Agostino1, F. Gulminelli2, Ad. Raduta3, F. Gramegna4, M. Bruno1, G. Baiocco1,L. Bardelli5, S. Barlini5, M. Bini5, F. Cannata1, G. Casini5, M. Chiari5, M. Cinausero4,

M. Degerlier4, E. Geraci6, V. L. Kravchuk4, T. Marchi1, P. Maurenzig5, L. Morelli1,A. Nannini5, P. Napolitani2, A. Olmi5, A. Ordine7, G. Pasquali5, G. Poggi5, V. Rizzi4,

G. Vannini1

(NUCL-EX collaboration)

(1) Dipartimento di Fisica dell’Universita and INFN, Bologna,Italy,(2) LPC Caen IN2P3-CNRS/EnsiCaen et Universite, Caen, France,

(3) NIPNE, Bucharest-Magurele, POB-MG 6, Romania,(4) INFN, Laboratori Nazionali di Legnaro, Italy,

(5) Dipartimento di Fisica dell’Universita and INFN, Firenze, Italy,(6) Dipartimento di Fisica dell’Universita and INFN, Catania, Italy,

(7) INFN, Sezione di Napoli,Italy,

Abstract

As anticipated in our Letter of Intent (presented to this PAC in July 2008),our main goal is the experimental determination of the symmetry energy at finitetemperature and/or sub-saturation density, which is one of the research themes tobe explored with stable and radioactive beams, such as those that will be deliveredby SPES at LNL.

We have shown that, to reach this goal, it is essential to recover informationon primary configurations. An important step in this direction will be achievedby measuring the population of low-lying discrete particle-unstable levels. Thisinformation can be extracted from relative kinetic energy correlation functions ofisotopically resolved charged products.

We present here a plan for an experimental campaign at ALPI, starting withthe reaction 32S +40 Ca at 17.7 A MeV incident energy. We require 12 days ofpulsed 32S beam with a beam current of about 1 pnA on target (III Hall).

The beam-time has been calculated on the basis of the estimated cross sectionfor the formation in central collisions of a source with excitation energy about 4A MeV. The detection efficiency, the beam intensity, the thickness of the targetand the statistics needed to calculate correlation functions have been taken intoaccount.

The experiments will be performed with the Ring-Counter [1], coupled toGarfield [2] (now fully equipped with digital electronics) with a nearly-4π cov-erage.

To improve the efficiency of the apparatus we have updated the Ring-Counterdevice to increase its granularity and performances. The renewed apparatus willbe under beam for the commissioning in few days (June 17-th).

1

7/23

Proposal

Precision lifetime study in the neutron-rich N = 84 isotone 140Ba from

DSAM measurements following Coulomb-barrier α-transfer reactions on a136Xe beam with the AGATA-Demonstrator

J. Leskea, G. Rainovskib, L. Coquarda, Th. Krolla, O. Mollera, Th. Mollera,

Nanninic, N. Pietrallaa and the AGATA collaboration

a TU Darmstadt, D-64289, Darmstadt, Germanyb

Dept. of Physics, Univ. of Sofia, 1164 Sofia, Bulgariac

Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, 50019 Sesto Fiorentino, Italy

1 Motivation and physics case

The residual proton-neutron interaction is well known to govern the evolution of shell struc-ture and the formation of nuclear collectivity. The dominant pn-quadrupole-quadrupoleinteraction in the valence shell can sensitively be studied through the properties of the one-quadrupole phonon 2+ state with mixed proton-neutron symmetry [1]. The nucleus 140Bawas one of the N=84 isotones for which Hamilton [2] has initially proposed the existenceof such a 2+ mixed-symmetry state near 2 MeV excitation energy from the analysis ofsmall E2/M1 multipole mixing ratios. Except for 140Ba, the other two stable cases (144Ndand 142Ce) were confirmed by lifetime data [1 and ref.s therein]. In 140Ba the 2+

3state is

suggested as the 2+

1,ms [2]. As already mentioned this assignment is based only on the smallmultipole mixing ratio of the 2+

3→ 2+

1transition [2]. The crucial experimental information,

namely the lifetime of this level is still missing. This information will allow for extractionof the absolute M1 transition strength, which provides the basis for a safe identificationof MSSs. Not a single mixed-symmetry state could ever unambiguously be identified in aradioactive nucleus from the absolute large M1 transition strength. The main reason forthis comes from the fact that the determination of the lifetimes of these highly excited,off-yrast states comprises a real experimental challenge. The case of 140Ba is particularlyinteresting because this isotope lies at the beginning of a region with pronounced octupolecollectivity and it would enable us to study strong F-vector E1 transitions [3] originat-ing from quadrupole-octupole coupling in the presence of isovector-type mixed-symmetrystates.

In this respect, developing new methods for population of MSSs, in particular, thosethat could potentially be applied to radioactive isotopes, is extremely important. Recently,it has been predicted [4] that α-transfer reactions may be an efficient way to populateMSSs, in particular in spherical nuclei. In Ref. [4] analytical expressions for α-transfercross-sections have been derived for the SU(3) and U(5) dynamical symmetries of the Inter

8/23

Proposal

Determination of the relative quadrupole moments of the one-phonon

mixed symmetry states in 94Mo and 96Ru using Coulomb excitation ininverse kinematics

N. Pietrallaa, C. Bauera, Th. Krolla, J. Leskea, O. Mollera, Th. Mollera, A.

Nanninic, G. Rainovskic and the AGATA collaboration

a TU Darmstadt, D-64289, Darmstadt, Germanyb

Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, 50019 Sesto Fiorentino, Italyc

Dept. of Physics, Univ. of Sofia, 1164 Sofia, Bulgaria

1 Motivation and physics case

The aim of the proposed experimental campaign is to measure the unknown quadrupole mo-ments of the first 2+ states and the one-phonon mixed-symmetry state (MSS) in Coulombexcited 94Mo and 96Ru ions. Proton-neutron (pn) mixed-symmetry states provide impor-tant information on the effective proton-neutron interaction in collective nuclei [1]. Theirexcitation energies are directly related to the proton-neutron symmetry energy in the nu-clear valence shell. Available information on MSSs of vibrational nuclei have recently beensummarized in a review article [2]. The dominant fragments of the one-phonon 2+

1,ms stateare typically observed at about 2 MeV excitation energy with a suvbstantial E2 matrixelement to the ground state. Due to their isovector character, MSSs decay rapidly bydipole transitions and are very short lived, typically a few tens of femtoseconds. Large M1matrix elements of ≈ 1 µN are in fact the unique signature for MSSs. The best examplesare found in the mass A≈90 regions [2, 4, 5, 6, 7, 8, 9, 3, 10]. Besides the one-phonon2+

1,ms state, the lowest-energy two-phonon 1+

1,ms and 3+

1,ms states are of utmost theoreticalimportance. Together, these three states completely specify the three parameters of theIBM-2 Majorana operator. Only two out of these three key states with mixed-symmetrycharacter have been systematically investigated up to now. The 1+

1,ms state is known asthe M1 scissors mode in deformed nuclei. The mixed-symmetry 3+ state has firmly beenidentified on the basis of large absolute M1 transition rates up to now only in one nucleus,the N = 52 nuclide 94Mo [3] with a level energy of 2965 keV. A promising candidate foranother 3+

ms state has been proposed at 2896 keV excitation energy in the N = 52 isotone96Ru on the basis of its similar decay pattern [12]. Other credible candidates for a 3+

ms stateare unknown until now [2]. The reason for this unsatisfactory lack of knowledge comes fromthe fact that unlike the 1+

1,ms and 2+

1,ms states the 3+

ms state cannot be populated directlyand selectively in electromagnetic excitation processes and requires a two-step excitationpath in Coulex.

On the basis of our successful method for identifying and investigating one-phonon 2+

1,ms

9/23

Inclusive and exclusive breakup measurement

for the system 7Be +

58Ni at near-barrier energies

M. Mazzocco1, L. Acosta

2, R. Berjillos

2, J. Duenas

2, F. Farinon

3, D. Filipescu

4, T. Glodariu

4,

A. Guglielmetti5, G. Inglima

6,7, M. Ivascu

4, M. La Commara

6,7, I. Martel

2, C. Mazzocchi

5,

P. Molini1, A. Pakou

8, C. Parascandolo

6,7, N. Patronis

8, D. Pierroutsakou

7, M. Romoli

7,

A.M. Sanchez-Benitez2, M. Sandoli

6,7, C. Signorini

1, R. Silvestri

6,7, F. Soramel

1, L. Stroe

4,

E. Vardaci6,7

, K. Zerva8

1Dipartimento di Fisica, Università di Padova and INFN, Padova, Italy

2Univesity of Huelva, Huelva, Spain

3GSI, Darmstadt, Germany

4NIPNE, Bucharest, Romania

5Dipartimento di Fisica, Università degli Studi di Milano and INFN, Milano, Italy

6Dipartimento di Scienze Fisiche, Università “Federico II”, Napoli, Italy

7INFN - Sezione di Napoli, Napoli, Italy

8Department of Physics, University of Ioannina, Ioannina, Greece

Abstract

We propose to investigate the inclusive and exclusive breakup processes for the system 7Be

+ 58

Ni at energies around the Coulomb barrier. 7Be is a very loosely bound Radioactive Ion Beam

(S! = 1.586 MeV) and it has a large probability to break into two stable charged fragments, 3He and

4He, in the proximity of a strong Coulomb or nuclear field. The fact that both

7Be breakup

fragments are stable and very well-bound makes this channel the cleanest breakup case that can be

studied among all light ions.

The DINEX detector array will be used to measure the angular and energy distributions of

the breakup fragments and of the 7Be scattered particles (for normalization purposes). The inclusive

and exclusive breakup cross sections will be deduced from the single and coincidence detection,

respectively, of 3He and

4He fragments.

The 7Be secondary beam for this experiment will be produced from a 31 MeV

7Li primary

beam delivered from the LNL-Tandem accelerator impinging on a H2-filled gas target. The

EXOTIC facility will be used to select the 7Be ions and to focus them on a

58Ni secondary target.

We will perform the measurement at two colliding energies: 20 MeV (nominal Coulomb barrier)

and 24 MeV.

10/23

Deformations of 48Cr composite nuclei produced via 24Mg + 24Mg reactions

A. Brondi, G. Campaiola, A. Di Nitto, G. La Rana, R. Moro, P. Nadtochy, E. Vardaci, INFN and Dipartimento di Scienze Fisiche dell’Università di Napoli, I-80126 Napoli, Italy

M. Cinausero, G. Prete

Laboratori Nazionali di Legnaro, I-35020 Legnaro (Padova), Italy

N. Gelli, F. Lucarelli

INFN and Dipartimento di Fisica dell’Università di Firenze, I-50125 Firenze, Italy

Abstract

The phenomena of clustering leading to large deformations have recently raised much interest. These phenomena have been enlightened by the observation of relatively narrow resonances in the elastic and inelastic channels for α-like nuclei. One possible interpretation of these structures is that they correspond to states of very large deformations in the dinuclear system, acting as doorway states to fusion reactions. These states could affect the evaporative decay as indicated by recent studies on 58Ni, 32S and 40Ca nuclei, for which unexpected large deformations have been found. We propose to study nuclear deformations of 48Cr at two excitation energies: Ex~60 and 70 MeV, produced in the reaction 24Mg + 24Mg at Elab=91.7 and 110. MeV, respectively. The first energy corresponds to the J=36+ resonance, while the second one is off the resonance region. The comparison of the evaporation residue-light charged particle correlations, as well as the particle-particle correlations and energy spectra at the two energies and with the predictions of the statistical model is expected to be particularly elucidating for such investigation. On the basis of the model, these observables are expected to be fairly sensitive on nuclear deformations. Beam request: total of 7 days of 24Mg Tandem pulsed beam for the two energies: Elab= 91.7 and 110 MeV.

11/23

Probing the 17F+p potential by (p,p) and (p,p') reactions at

near barrier energies

N. Patronis, A. Pakou, N. G. Nicolis, K. ZervaDepartment of Physics, The University of Ioannina, 45110 Ioannina, Greece

I. Martel, L. Acosta, R. Berjillos, J. Duenas, A.M. Sanchez-BenitezDapartamento di Fisica Atomica Molecular y Nuclear, Universidad de Huelva, E-21071

Huelva, Spain

D. Pierroutsakou, M. RomoliINFN - Sezione di Napoli. Italy

G. Inglima, M. La Commara, C. Parascandolo M. Sandoli, E. Vardaci Dipartimento di Scienze Fisiche and INFN Sez. di Napoli, Universit di Napoli, via Cinthia,I-80126,

Napoli, Italy

M. Mazzocco, P. Molini, C. Signorini, F. SoramelDipartimento di Fisica and INFN Sez. di Padova, Universit di Padova, via Marzolo 8,

I-35131 Padova, Italy

A. Guglielmetti, C. MazzocchiDipartimento di Fisica and INFN Sez. di Milano, Universit di Milano, via Celoria 16,

I-20133, Milano, Italy

N. AlamanosCEA-Saclay, DAPNIA-SPhN, Gif-sur-Yvette, France

K. Rusek, N. Keeley, A. TrzcinskaHeavy Ion Laboratory, University of Warsaw , Pasteura 5a, 02-093 Warsaw

andDepartment of Nuclear Reactions, The Andrzej So ltan Institute for Nuclear Studies,

Ho_za 69, 00-681 Warsaw, Poland

T. Glodariu, D. Filipescu"Horia Hulubei" National Institute of Physics and Nuclear Engineering , Romania

M. KokkorisNational Technical University of Athens, Greece

E. StiliarisInstitute of Accelerating Systems and Applications and Department of Physics,

University of Athens, Greece

ABSTRACT

Proton elastic and inelastic scattering angular distributions on 17F will be measured over a

wide angular range (CM=200-1600), in inverse kinematics at 45, 55 and 65 MeV, an energy

region presenting strong interest form the astrophysical point of view. The aim of the measurement is the determination of the 17F+p potential and of total reaction cross sections. Efforts will be also directed to deduce the ratio of proton to neutron deformation of the 17F first excited state, as a signature of the exotic shape for this nucleus.

12/23

Istituto Nazionale di Fisica Nucleare

Laboratori Nazionali di Legnaro

Tandem-ALPI Accelerator

PROPOSAL

Trapping of Radioactive Francium Atoms with aMagneto–Optical Trap

Spokespersons: R. Calabrese, L. Moi

List of participants:

S. N. Atutov, R. Calabrese, L. Tomassetti

INFN and Universita di Ferrara

L. Corradi, A. Dainelli

INFN Laboratori Nazionali di Legnaro

P. Minguzzi, S. Sanguinetti

CNISM and Universita di Pisa

A. Bogi, A. Burchianti, A. Khanbekyan, C. Marinelli, E. Mariotti, L. Moi

INFN, CNISM and Universita di Siena

14 giugno 2009

Abstract

The apparatus for the production and trapping of francium is briefly

described together with the results we have obtained in trapping of 209,

210, 211 Francium isotopes. Beam time is requested to continue the

studies on the trapping efficiency optimization and on the search for

new radiative transitions.

13/23

Gasp + RFD Experiment

Octupole deformation versus Heart shape waves :

High spin and Lifetime measurement in the opposite parity bands of 219

Th

and 220

Th

S.Aydin, D.Bazzacco, E. Farnea, S. Lenzi, S. Lunardi, D. Mengoni, R. Menegazzo, C. Ur, F.

Recchia

INFN and Dipartimento di Fisica, Universita’ di Padova, Italy

G. de Angelis, D.R. Napoli, E. Sahin, J.J. Valiente-Dobon,C. Michelagnoli, A. Gottardo,

LNL, INFN, Legnaro, Italy

S.Erturk, B.Ozel, V,Bozkurt, B.Gokuzum

Department of Physics, Nigde University, Nigde, Turkey

A. Gadea

IFIC Valencia, Spain

P. Bednarczyk, W. Meczynski

Istitute of Nuclear Physics, Krakow, Poland

M. Palacz,G. Jaworski, J.Mierzejewski

Heavy Ion Laboratory, Warsaw, Poland

D. Tonev

INRNE, Sofia, Bulgaria.

J.F. Smith, R. Orlandi, R. Chapman, B. Hadinia, A. Hodsdon, K.M. Spohr and D. Torres

University of the West of Scotland Paisley, UK

Th nuclei is among the best examples of reflection asymmetric nuclear shapes. Here the

existence of well developed alternating parity states has been taken as the evidence for stable

octupole deformation. Recently, a detailed analysis of the behaviour of such bands has led to

the hypothesis of a rotation-induced condensation of octupole phonons. To verify this

theoretical description we propose to investigate the high spin structure of 219

Th and 220

Th and

to determine the absolute transition matrix elements of the E1 transitions de-exciting the states

of the opposite parity bands in the spin region where octupole deformation arises. Excited

states in 219

Th and 220

Th will be populated using the 198

Pt(26

Mg, 5n and 4n) reaction channels.

Gamma coincidence data will be taken using the Gasp array coupled to the Recoil Filter

Detector. Lifetimes (from few fs to 500 fs) will be determined from the analysis of the line

shape of the gamma rays emitted by the ions traversing the target. Beyond this goal, we also

aim to do a spectroscopic study of 219

Th. In a previous experiment with similar conditions

we have newly identified γ-ray transitions of 219

Th. With more statistics it should now be

possible to build the level scheme of this nucleus. The limited results of the previous

experiment were mainly due to the performances of the accelerator which has delivered a

lower beam current than expected as well as to the low performance of the RFD, which has

been recently repaired. To accomplish such goal we ask for 5 days of Tandem beam time.

14/23

Shape changes in the light barium isotopesGASP PROPOSAL

Spokespersons: C. Michelagnoli and C. A. Ur

List of participants:

C. A. Ur, E. Farnea, S. Aydin, D. Bazzacco, F. Brandolini, S. M. Lenzi,

S. Lunardi, R. Menegazzo, D. Mengoni, F. Recchia, C. Rossi Alvarez

INFN e Dipartimento di Fisica dell’Universita di Padova

C. Michelagnoli, G. de Angelis, A. Gottardo, D. R. Napoli, E. Sahin,

J. J. Valiente–Dobon

INFN, Laboratori Nazionali di Legnaro

O. Moller

Technische Universitat Darmstadt

P. G. Bizzeti, A. M. Bizzeti–Sona, A. Giannatiempo, A. Nannini, A. Perego,

P. Sona

INFN e Dipartimento di Fisica dell’Universita degli Studi di Firenze

A. Gadea

IFIC Valencia

A. Dewald, B. Melon, T. Pissulla

Institut fur Kernpysik der Universitat zu Koln

Abstract

We propose to measure the lifetimes of the yrast states in the region of backbending

and above it in 124Ba by means of the Doppler Shift Attenuation Method, by using the

GASP array in configuration II. The quadrupole deformation parameters estimated on

the basis of this measurement will allow for a deeper understanding of the deformation–

driving properties of the h11/2 proton orbitals in this mass region. The states of interest

will be populated via the 112Cd(16O,4n)124Ba reaction. A beam energy of 84 MeV seems

to strike a balance between a sufficiently high statistics for high–energy gamma–rays and

a low enough recoil velocity to avoid the overlap between the lineshapes of the intra-

band transitions that are close in energy. Four days are necessary to obtain a significant

statistics for the transitions of interest.

15/23

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16/23

Study of T = 1 isospin triplets of mass 30 and 34

Ritesh Kshetri1,2, C. Andreoiu1, R.A.E. Austin3, G.de Angelis4, S. Aydin5, G.C. Ball2, D.S.

Cross1 , B. Davids1,2, M. Djongolov2, H.Al Falou2, A.B. Garnsworthy2, P.E. Garrett6, A.

Gottardo4, G. Hackman2, S.M. Lenzi5, R. Menegazzo5 , D. Mengoni4, C. Michelagnoli4, D.R.

Napoli4, J.N. Orce2 , F. Recchia4, M. Saha Sarkar7, G.E. Sahin4, S. Sarkar8, S.K.L. Sjue2,

C.E. Svensson6, S. Triambak2, C.A. Ur5, J.J. Valiente Dobon4, S.J. Williams2, J.L. Wood9

1Simon Fraser University, Burnaby, B.C., Canada2TRIUMF, Vancouver, B.C., Canada

3Saint Mary’s University, Halifax, Nova Scotia, Canada4INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy

5Dipartimento di Fisica dell’ Universita and INFN, Padova, Italy6University of Guelph, Guelph, Ontario, Canada

7Saha Institute of Nuclear Physics, Kolkata, India8Bengal Engineering and Science University, Shibpur, Howrah, India and

9Georgia Institute of Technology, Atlanta, Georgia, USA

Abstract: We propose to study the excited states in the T = 1 isospin triplets of mass 30 and 34, which

represents the first study of T = 1 isospin triplet for high spins states of sd−shell nuclei. The 24Mg+12C

reaction at a beam energy of 124 MeV will be utilised. The experimental set-up is composed of the GASP

spectrometer, the Euclides charged particle detector and the neutron ring. The identification of excited states in

these nuclei will allow us to investigate the isospin symmetry in nuclei close to N ≈ Z, along with testing the

shell model. The angular dependance of isovector and isotensor Coulomb energy differences and level lifetimes

will be studied along with searching for possible evidences of symmetry breaking. The study also aims to look

for deformed states in 34Ar. 30S lies on the rp−process path and spectroscopic information of states above the

proton threshold is essential in the stellar reaction rate calculations.

17/23

GASP Proposal

Lifetime measurement of the 6.792 MeV state in 15O

Spokespersons: Roberto Menegazzo, Calin A. Ur

List of participants:

S. Aydin, F. Recchia, C. Broggini, A. Caciolli, M. Erhard, R. Menegazzo, C.A. Ur

INFN and Università di Padova, Padova, Italy

A. Gottardo, D. Mengoni, C. Michelagnoli, E. Sahin

INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy

D. Bemmerer, M. Marta

Forschungszentrum Dresden-Rossendorf, Dresden, Germany

G. Gyürky, T. Szücs, Zs. Fülöp

ATOMKI, Debrecen, Hungary

Abstract

The capture reaction 14N(p,!)15O (Q = 7297 keV) is the slowest process in the hydrogen

burning CNO cycle and thus of high astrophysical interest. At stellar energies one expects

a significant contribution to the ground state astrophysical S-factor from the sub-

threshold resonance at ER = -504 keV, corresponding to the known Ex = 6.792 MeV state

in 15O. We propose to measure the mean lifetime of this state via the Doppler-Shift

Attenuation (DSA) method. The 15O nucleus will be populated in the 2H(14N,15O)n

reaction and the emitted !-rays will be detected with GASP in configuration II with an

additional Compton suppressed HPGe detector placed at 0° (i.e. along the beam

direction). The target will consists of deuterium implanted into a thick Au substrate, also

used to slow down the recoiling 15O nuclei. The initial beam energy, Ebeam = 32.2 MeV,

will be reduced to 22.5 MeV placing a thin Au layer before the target. Ten days of 14N

beam on target would be necessary to obtain the required statistics.

18/23

GASP + RFD proposal

- 1 -

Study of the anomalous behavior of the Coulomb energy difference in the

A=70, T=1 izobaric multiplet

M. Matejska-Minda, P. Bednarczyk, M. Ciemała, B. Fornal, M. Kmiecik, A. Maj, W. Męczyński,

S. Myalski, J. Styczeń, M. Ziębliński The H. Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland

G. de Angelis, E. Farnea, R. Menegazzo, D. Napoli, F. Recchia, C. Ur, J.J. Valiente-Dobon LNL, INFN Padova, Italy

A. Bracco, G. Benzoni, N. Blasi, F. Camera, A. Corsi, F. Crespi, S. Leoni, B. Million, D. Montanari,

R. Nicolini, O. Wieland Università degli Studi e INFN sezione di Milano, Milano, Italy

G. Jaworski, J. Mierzejewski, M. Palacz

HIL, University of Warsaw, Poland

A. Gadea IFIC, Valencia, Spain

R. Wadsworth University of York, York, UK

By the current document we resubmit the proposal number 09.05 accepted

previously by the LNL PAC.

The experiment has been performed, however due to a failure of the data acquisition

system in the course of the measurement, most of the collected data was not correctly

recorded and can not be used.

Results of analysis based on the incomplete data set are promising. They are

summarized in the Appendix.

Abstract:

We propose studies aiming at the spectroscopy of proton rich nuclei around the N=Z=35

nucleus 70

Br.

The Br/Se A=70 isobar pair shows a unique behavior since the Coulomb energy difference

(CED) seems to drop gradually with spin. Such an effect could be associated with significant

shape changes with increasing angular momentum.

The goal of the proposed measurement is to provide information on the excited states and

lifetimes along the T=1 isobaric analogue bands in the N=Z 70

Br and in the N=Z+2 70

Se

nuclei and study of the behavior of CED in this A = 70 isobaric multiplet.

We are going to use the 40

Ca(32

S, pn )70

Br and 40

Ca(32

S ,2p) 70

Se reactions with a thin 40

Ca target and the beam energy of 95 MeV. Gamma-rays will be measured in GASP. An

important issue of the proposed experiment is the use of the RFD detector coupled to GASP.

It will be used to detect fast recoiling nuclei in coincidence with γ-rays. The coupled GASP-

RFD set-up will provide great reduction of Doppler broadening, allowing extensive filtering

out of γ-rays originating from background reactions on target impurities (mostly oxygen and

carbon) and determination of lifetimes in the ps range.

We ask for 5 days of beam time with a pulsed 32

S beam.

19/23

Inelastic scattering as a tool to search for highly excited states up to the region of the Giant Quadrupole Resonance

A. Braccoa, G. Benzonia, N. Blasia, C. Boianoa, S. Brambillaa, F. Cameraa, A. Corsia, F.C.L. Crespia, S. Leonia, B. Milliona, D. Montanaria, R. Nicolinia, S. Riboldia, O. Wielanda, G. De Angelisb, A. Gadeab,d, D. R. Napolib, F. Recchiab, J.J. Valiente-Dobonb, D. Bazzaccoc, E. Farneac, D. Mengonic, A. Maje, M. Kimiecike , M. Ciemalae , G. DeFrancef, F. Azaiez et al.g a Università degli Studi e INFN sezione di Milano, Via Celoria 16, 20133, Milano. b INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy. c Università di Padova e INFN, sezione di Padova, Padova, Italy. d IFIC, Valencia, Spain. e The Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland f GANIL Laboratory, Caen, France g IN2P3, Orsay, France

Spokepersons: R. Nicolini, D. Mengoni

Abstract

We propose an AGATA-Demonstrator (AD) experiment to study of the gamma decay from giant resonances at zero temperature in 208Pb and 90Zr. The experiment aims at the measurement of a known case first (208Pb), but with improved experimental conditions in particular concerning the energy resolution of the gamma detections. In addition, in contrast to the existing measurement concentrating mainly on the decay of the giant quadrupole resonance (GQR) in the 10-13 MeV range, we intend to measure the GQR with high resolution together with the lower excitation energy region between 5 to 10 MeV, where pygmy dipole structures exist but not all of them are yet well identified. The giant resonance modes will be excited by inelastic scattering of 17O at 20 MeV/A (the highest energy available at LNL) on 208Pb and 90Zr targets, 2 mg/cm2 thick. The scattered ions will be detected by one E-E Si telescope of the TRACE project, while the -decay from the GQR will be measured by the AD coupled to an array of large volume scintillator detectors (BaF2 and LaBr3). The proposed experiment follows a test measurement, performed in June 2009 at the AD measurement point, aiming at testing the performances of the TRACE telescopes, consisting of Si-pixel detectors. We request 8 days of beam time: 1 for setup and 7 for data taking.

20/23

Istituto Nazionale di Fisica Nucleare Laboratori Nazionali di Legnaro

TANDEM XTU-PIAVE-ALPI ACCELERATOR.

Proposal PAC 09/

Test of Prisma operation at 0° in Gas-Filled Mode

F.Scarlassara1, P.Mason1, G.Montagnoli1, E.Fioretto2, A.M.Stefanini2, L.Corradi2, G.Pollarolo 3,

S.Szilner4

1) Università di Padova and INFN, sezione di Padova, I-35131 Padova, Italy

2) INFN, Laboratori Nazionali di Legnaro. I-35020 Legnaro (Padova), Italy

3) INFN and Università di Torino, Torino, Italy

4) Ruder Boskovic Institute, HR-10001 Zagreb, Croatia

Spokesperson: F.Scarlassara

Abstract.

In a first test performed in 2007 we proved that prisma can be operated as a gas-filled magnetic

separator, a mode a operation characterized by a large transmission and beam rejection. However

successful, the test was rather a proof of principle since it avoided the critical aspects connected

with operation at zero degrees, which is what a gas filled separator (GFS) is supposed to do.

We propose to complete the commissioning of Prisma as a GFS, by detecting fusion evaporation

residues at 0°. A total of three days beamtime are requested.

With the PRISMA experiment one year ahead of its conclusion, it is important to explore this

option, which would open interesting possibilities for the future, also in view of the unstable beams

from SPES.

21/23

Proposal for the Tandem-ALPI accelerator

Spokesperson: E. Fioretto

Kinematic coincidence measurements in conjunction with the PRISMA spectrometer

E. Fioretto, L. Corradi, A.M. Stefanini INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro, Italy

E. Farnea, P. Mason, C. Michelagnoli, G. Montagnoli, F. Scarlassara, C.A. Ur Dipartimento di Fisica, Università di Padova, and INFN, I-35131Padova, Italy

D. Jelavić, M. Milin, N. Soić, S. Szilner Ruđer Bošković Institute, HR-10002 Zagreb, Croatia

G. Pollarolo Dipartimento di Fisica Teorica, Università di Torino, and INFN, I-10125 Torino, Italy

N. Marginean Horia Hulubei National Institute of Physics and Nuclear Engineering, 077125, Bucharest, Romania

D. Gorelov, Yu. Itkis, G. Knyazheva, E. Kozulin, Flerov Laboratory of Nuclear Reactions, JINR, 141980, Dubna, Moscow Region, Russia

Abstract

We propose to perform an experiment devoted to kinematic coincidence measurements

between binary reaction products populated with the 90

Zr+208

Pb system at energies close to the

Coulomb barrier. Projectilelike fragments, identified at the focal plane of the large solid angle

magnetic spectrometer PRISMA, will be used to tag heavy partners entering into a 2-dimensional

position sensitive device (providing also the total energy) located at the correlation angle in the

scattering chamber. This experiment will allow to extract the survival probability against fission

and the mass distributions of the heavy fragments as a function of Z, A of the light fragments and

Q values derived from PRISMA. Two beam energies are required to follow how the fission

probability evolves as a function of the excitation energy. This is important to get quantitative

estimates for the production rate of the heavy partners and to check the feasibility to use the

multinucleon transfer process as a tool to populate high Z elements in future experiments.

22/23

1

Istituto Nazionale di Fisica Nucleare Laboratori Nazionali di Legnaro

TANDEM ACCELERATOR

PROPOSAL PAC 09/ ..

Quest for Nuclear Tidal Waves in 112Te

F. Recchia, S. Aydin, D. Bazzacco, E. Farnea, A. Gottardo, S. Lenzi, S. Lunardi, R. Menegazzo, D. Mengoni, C.A. Ur

University and INFN-Sezione di Padova, Italy A.Gadea, A.Algora

IFIC, CSIC – University of Valencia, Spain J.J.Valiente-Dobón, G.de Angelis, D.R.Napoli, E.Sahin, C.Michelagnoli

INFN-Laboratori Nazionali di Legnaro, Padova, Italy T. Pissulla, A.Dewald, B. Melon, M. Hackstein, W. Roether

IKP University of Cologne, Germany S. Frauendorf, Yingqiong Gu

Department of Physics, University of Notre Dame, IN, USA B.Quintana, M.Doncel, I.Sagrado

LRI – University of Salamanca, Spain

Abstract Shape evolution and the mechanisms of generating angular momentum are major topics in nuclear structure research. In the collective model, vibrational and rotational modes differ by the way of producing angular momentum. There exists a large group of transitional nuclei that show intermediate behaviour between harmonic vibration and rotation. The description of the structure of these nuclei has been a long standing challenge to nuclear theory and has triggered the development of theories based on spontaneous symmetry breaking as well as based on the dynamic symmetries. The new concept of nuclear tidal waves allows calculating, by means of the microscopic cranking model, a sequence of states, with maximal angular momentum, each one corresponding to a tidal wave, i.e. a static deformation in the rotating frame of reference. To identify regions where nuclear tidal waves phenomena occur will help to strengthen the predictive power of the model. From a systematic study of transitional regions the 112Te nucleus has been identify as a good candidate for this phenomena in a region different form the previously known case of the 110Cd. The present proposal aims measuring half-lives of nuclear states in the picoseconds range to prove the nuclear Tidal wave nature of the 112Te yrast band. The nucleus 112Te will be populated in a fusion-evaporation reaction using a 58Ni TANDEM beam, with an energy of 215 MeV, impinging on a 1 mg/cm2 58Ni RDDS target from the IKP-Köln plunger. The emitted γ-rays will be measured with the GASP Ge-array.

23/23