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L.M. Robledo et al., J. Phys. G: Nucl. Part. Phys. 36 (2009) 115104

L.M. Robledo et al., J. Phys. G: Nucl. Part. Phys. 36 (2009) 115104. Main physics aim is to study the best cases of nuclear triaxial rotation to finite spin. 190,192 W are predicted to be among the most gamma-soft, deformed nuclei in the entire nuclear chart.

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L.M. Robledo et al., J. Phys. G: Nucl. Part. Phys. 36 (2009) 115104

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  1. L.M. Robledo et al., J. Phys. G: Nucl. Part. Phys. 36 (2009) 115104 Main physics aim is to study the best cases of nuclear triaxial rotation to finite spin. 190,192W are predicted to be among the most gamma-soft, deformed nuclei in the entire nuclear chart.

  2. Calculations suggest almost gamma-flat potential for N=116 190W

  3. 188W 190W 192W N. Alkhomashi et al., Phys. Rev. C80 (2009) 064308 TRS calculations for w = 0 MeV / ħ are also consistent with b2~0.15; gamma=flat

  4. 208Pb target DIC (see proposal by Zsolt Podolyak) 192Os target DIC Stopped RISING Experiments @ GSI (2006-8): 27 ‘new’ isomers (48 total) measured in a wide range of neutron-rich nuclei. Beta-delayed studies also…. RISING: isomeric and beta decays AGATA+PRISMA: prompt S.Steer, Zs. Podolyak, P.H. Regan et al., Int. Jour. Mod. Phys. E18 (2009) 1002

  5. Knowledge to date ?

  6. 188Ta →188W 190Ta →190W 192Ta →192W N. Alkhomashi et al., Phys. Rev. C80 (2009) 064308

  7. bubble! 192W Evidence for a ‘sub – shell’ closure for Z=74 (or lighter ?) 190W R.B.Cakirli & R.F. Casten Phys. Rev. C78 (2008) 041301 (R)

  8. Minimization of gamma-softness at N=116 ? W isotopes

  9. Davydov-Fillipov Model, low-lying Ip=2+2 is evidence for large g degree of ‘deformation’. Wilet-Jean (soft rotor) for g flat also have low-lying 2+2 state.

  10. Knowledge to date on 190W is from b- and isomer delayed spectroscopy. Spins are limited

  11. vacuum only 2qp states included Higher Spins in 190W ?

  12. Prediction of a GIANT BACKBEND associated with abrupt prolate-to-oblate transition around 10 ħ. Favoured oblate collective rotations predicted for spins above this…..

  13. Proposal to identify near-yrast states in 190,2W to >10ħ. Suggested reaction parameters: 136Xe +192Os →136-yBa + 192-xW E(136Xe) = 809 MeV from PIAVE; I(136Xe) ~2pna; 192Os target thickness = 0.5mg/cm2 BLF ~ 8% v/c; TLF ~ 6.7%; lmax(TLFroll)~39 ħ; lmax(BLFroll)~35 ħ Gate on • Barium (Z=56) binary partners in PRISMA and • Barium (134,136,138Ba) isomers stopped in DANTE. • Use 2-body kinematics for W isotope Doppler correction. (assumes 20% above Coulomb barrier; can run with 900 MeV for better transmission / id in prisma.)

  14. Reaction of choice would be 192Os+136Xe -> 192-XW+136Ba Prompt and delayed gammas in 136Ba have been identified and can be used for tagging.

  15. 136Ba Isomer gate in 136Xe+198Pt ‘in-beam’ DIC reaction, clearly identifies (all previously reported) 198-xOs isotopes. Would expect the same from 136Ba isomer gate at target position from ions stopped in DANTE. Note, can also use 134Ba & 138Ba isomers as ‘tungsten tags’ too.

  16. Rate estimate / beam-time request: Expect using the estimates on the previous page: ~ 4k ‘useful’ PRISMA – (190,2W)-(190,2W) g2 coincidences per day + ~9.5k ‘useful’ DANTE-Ba-isomer- (190,2W)-(190,2W) g2 per day. TOTAL ~ 70,000 190,2W g2 clean coincidences from a 5 day run. Request 5 days beam-time plus one day for PRISMA calibrations and setting up.

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