Nasser Alkhomashi Dept. of Physics, University of Surrey Gu

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ß- Decays from 188, 190,192 Ta Shape
Evolution in Neutron-Rich Tungsten Isotopes
Nasser Alkhomashi Dept. of Physics,
University of Surrey Guildford, Surrey, GU2 7XH,
UK
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Relativistic beams at GSI

• accelerators
• UNILAC (injector) E11.4 MeV/n
• SIS - E lt 1 GeV/nucleon
• beams
• All ion species up to 238U
• Current
• 208Pb - 2 109 pps

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Time Of Flight (TOF) through FRS 300ns
Ion-by-ion identification using the FRS
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RISINGRare ISotope INvestigation at GSI
15 high-efficiency Cluster germaniums 14 at
661 keV
S. Pietri, et al., Acta Phys. Pol. B38, 1255
(2007)
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5 cm x 5 cm DSSSD (16 strips by 16 strips 256
pixels) 3 DSSSDs 3 positions across focal
plane.
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Detectors Configuration
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Experiment Aim

• 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.

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Charge states
190Ta 192Ta -settings
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Particle Identification
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Decays from known and new isomeric states prove
correctness of particle ID
189Ta
188Ta
191W
190W
193Re
192Re
previous isomeric study by M. Caamano et al.,
Eur. Phys. J. A23 (2005) 201
188Ta
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192Re ? 192Os adopted value T1/216(1) s see
Nucl. Data Sheets 84 (1998) p717
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Two-neutron Transfer Reactions 186W(18O,16O)
188W
T. Shizuma et al. ,Eur. Phys. J. A 30, 391396
(2006).
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NO Isomer
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Preliminary
Greg Lane et al. , ANU
t 290 ns
184
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Beta delayed spectroscopy of 188Ta ? 188W
Correlation time120 (s)
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Isomeric decay of 190W
Zs. Podolyak, et al., Phys. Letts. B, 491, 225
(2000). G. F. Farrelly, et al., Acta Phys. Pol. B
40 (2009) 885.
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Beta delayed spectroscopy of 190Ta ? 190W
Correlation time30 (s)
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Isomer gating on 190W
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The classic O(6) (?-soft) nucleus. What about
190W ?
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Beta delayed spectroscopy of 192Ta ? 192W
Correlation time15 (s)
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E(2) 190W 192Os E(2) 192W 194Os
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Conclusion

• 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 and 190W 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.

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Acknowledgement
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.
Grskac , I. Kojouharovc , H. Scha?nerc , 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 .
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, Germany d The H.
Niewodniczaski Institute of Nuclear Physics PAN,
Krakw e IFIC Valencia,
Spain f INFN, Universit degli
Studi di Milano, I-20133 Milano, Italy
g IKP, University of Cologne, D-50937
Cologne, Germany h School of Engineering,
University of Brighton, Brighton BN2 4GJ, UK
i Department of Physics, Osaka
University, Osaka, Japan j Department of
Physics, Lund University, S-22100 Lund, Sweden
k UAC, New Delhi,
India l University of Edinburgh, UK
m NIPNE, Bucharest,
Romania n Research Center for Nuclear Physics
(RCNP), Osaka University, Japan o
INFN-Laboratori Nazionali di Legnaro, Padova,
Italy
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192W
188W
190W
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E(2)2/E(2)1
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E(2)2 - E(4)1
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1/E(21)
R.B. Cakirli and R.F. Casten, Phys. Rev. C78
(2008) 041301(R).