Nasser Alkhomashi

Dept. of Physics, University of SurreyGuildford, Surrey, GU2 7XH, UK

β- Decays from 188, 190,192 Ta: Shape

Evolution

in Neutron-Rich Tungsten Isotopes

2

Relativistic beams at GSIaccelerators:

UNILAC (injector) – E=11.4 MeV/n

SIS - E < 1 GeV/nucleon

beams:

All ion species up to 238U

Current:

208Pb - ~2* 109 pps

primary beam

Pb @ 1GeV/u

Production target

Central focus, S2Final focus, S4

E(Z2)

cu

eB

Q

A

FTO

catcher

degrader

degrader

dipole, B

scintscint

MW=x,y

scint

(veto)

In-Flight Technique Using Projectile Fragmentation

Ion-by-ion identification using the FRS

Time Of Flight (TOF) through FRS: ~300ns

4

RISING

Rare ISotope INvestigation at GSI15 high-efficiency

Cluster germaniums

~14% at 661 keV

MUSIC MUSIC

Sci4

1

MW

41

MW

42

deg

rad

er

beam

S. Pietri, et al., Acta Phys. Pol. B38, 1255 (2007)

5

5 cm x 5 cm DSSSD (16 strips by 16 strips = 256 pixels)3 DSSSDs= 3 positions across focal plane.

Detectors Configuration

- Correlate implanted ions (mother) with -decay using the active, position sensitive, pixellaed

stopper.

- Measure rays (internal structure) from decays of

• ns-ms isomeric states in original implanted ion,

and / or

• excited states in -daughter nucleus.

Experiment Aim

190Ta192Ta188Ta

190Ta+ 192Ta -

settings

Charge states

Particle Identification

previous isomeric study by M. Caamano et al., Eur. Phys. J. A23 (2005) 201

191W190W

189Ta

193Re192Re

188Ta

Decays from known and new isomeric states

‘prove’ correctness of particle ID

192Re → 192Os adopted value T1/2=16(1) s see Nucl. Data Sheets 84 (1998) p717

Two-neutron Transfer Reactions 186W(18O,16O)

T. Shizuma et al. ,Eur. Phys. J. A 30, 391396 (2006).

188W

NO Isomer

Greg Lane et al. , ANU

τ= 290 ns

184

Preliminary

Beta delayed spectroscopy of 188Ta → 188W

Correlation time=120 (s)

Zs. Podolyak, et al., Phys. Letts. B, 491, 225 (2000).

G. F. Farrelly, et al., Acta Phys. Pol. B 40 (2009) 885.

Isomeric decay of 190W

Beta delayed spectroscopy of 190Ta → 190W

Correlation time=30 (s)

Isomer gating on 190W

190Ta (I=3-)

207 2+

564 4+

(454) (2+2)

0 0+

(247)357

207 454

190W

Possible level scheme for

190W by beta decay

The classic O(6)

(-soft) nucleus.

What about 190W ?

Ex 2nd 2+ States (gamma bandhead?)

0

200

400

600

800

1000

1200

1400

100 105 110 115 120

Neutron Number N

Excit

ati

on

en

erg

y (

keV

)

Hf (Z=72)

W (Z=74)

Os (Z=76)

Pt (Z=78)

190W ? 196Pt, O(6)

Beta delayed spectroscopy of 192Ta → 192W

Correlation time=15 (s)

E(2+): 190W = 192Os

E(2+): 192W = 194Os

Population of the 188W Isomeric state (7-) following the

beta decay of the mother nucleus 188Ta.

The measurement of the first excited states in 188W and190W confirmed the previous level schemes proposed for

these nuclei.

Evidence of 22+ state in 190W confirm the suggestion of

the gamma-soft rotor for this nucleus.

The 2+ state in 192W has been identified for the first time.

Conclusion

N. Alkhomashia , P.H. Regana , Zs. Podolyaka , S.B. Pietria , A.B. Garnsworthya , S.J. Steera , J. Benlliureb , E. Caserejosb

, J. Gerlc , H.J. Wollersheimc , J. Greboszd , G. Farrellya , M. G´rskac , I. Kojouharovc , H. Schaffnerc , A. Algorae , G.

Benzonif , A. Blazhevg , P. Boutachkovc , A.M. Bruceh , A. M. Denish , I.J. Cullena , M.E. Estevezb , Y. Fujitai , W. Gelletlya ,

R. Hoischenj , R. Kumark , S. Lalkovskih , Z. Liul , C. Mihaim , F. Molinae , D. Mucherg, P. D. Stevensona , E. Sucklinga , B.

Tamiin , S. Tashenovc , J.J. Valiente-Dobano , P.M. Walkera , P.J. Woodsl .

Acknowledgement

a Department of Physics, University of Surrey, Guildford GU2 7XH, UK.b Universidad de Santiago de Compostela, Santiago de Compostela, Spain

c GSI, Plankstrasse 1, D-64291 Darmstadt, Germanyd The H. Niewodniczaski Institute of Nuclear Physics PAN, Krakw

e IFIC Valencia, Spainf INFN, Universit degli Studi di Milano, I-20133 Milano, Italyg IKP, University of Cologne, D-50937 Cologne, Germany

h School of Engineering, University of Brighton, Brighton BN2 4GJ, UKi Department of Physics, Osaka University, Osaka, Japan

j Department of Physics, Lund University, S-22100 Lund, Swedenk UAC, New Delhi, India

l University of Edinburgh, UKm NIPNE, Bucharest, Romania

n Research Center for Nuclear Physics (RCNP), Osaka University, Japano INFN-Laboratori Nazionali di Legnaro, Padova, Italy

188W192W190W

E(2)2+/E(2)

1+

E(2)2+ - E(4)

1+

1/E(21+)

R.B. Cakirli and R.F. Casten, Phys. Rev. C78 (2008) 041301(R).