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Isomers and shape transitions in the n-rich A~190 region: Phil Walker University of Surrey prolate K isomers vs. oblate collective rotation the influence of angular momentum
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Segre chart with isomers adapted from Walker and Dracoulis, Nature 399 (1999) 35 K isomers (A ~ 170-190) Z=72 (Hf)
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prolate-oblate shape transition Robledo et al., J. Phys. G: Nucl. Part. Phys. 36, 115104 (2009). 0 n-rich hafnium ground states 60 γ 30 N = 116 critical point
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Hilton and Mang [PRL43 (1979) 1979] prolate oblate HFB calculations
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180 Hf oblate band? Tandel et al., Phys. Rev. Lett. 101 (2008) 182503 with Gammasphere three 20 + states pre-Gammasphere high-K yrast isomers: d'Alarcao et al., Phys. Rev. C59 (1999) 1227(R) 3600
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cranked n-rich hafnium: 3 well-deformed minima collective prolate non-collective prolate 182 Hf example: Xu, Walker and Wyss, Phys. Rev. C62 (2000) 014301 ћω = 0.2 ћω = 0.3ћω = 0.4 collective oblate
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190 Hf TRS oblate rotor ħω = 0 MeV ħω = 0.15 MeV ħω = 0.3 MeV ħω = 0.45 MeV prolate oblate I=32 Xu et al., unpublished beyond the critical point
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Hf prolate vs oblate 182 Hf 186 Hf prolate oblate mqp prolate [Xu et al., Phys. Rev. C62 (2000) 014301] prolate oblate
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Nilsson single-particle diagram N = 116 ( 188 Hf, 190 W, 192 Os) oblate prolate
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data for even-even A~190 nuclei 190 W 10 - ~1ms 192 Os 10 - 6s 186 W 16 + >3ms 7 - 20μs 190 Os 10 - 10m 188 W 182 Hf 13 + 40μs 8 - 62m 184 Hf 8 - 48s 184 W 15 0.2μs 5 - 8μs 188 Os 7 - 14ns 186 Os 7 - 8ns Z=76 Z=74 Z=72 N = 110 112 114 116 ? 188 Hf 186 Hf new data critical point
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W-190 gammas 190 W delayed gamma rays from 208 Pb fragmentation at 1 GeV per nucleon ~1 ms a critical point nucleus
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isomer energies, potential energy surfaces 190 Os 114 192 Os 116 190 W 116 (calc) (exp) 0+0+ 10 - 1633 2360±25 2015 6s 1920 1705 10m 1700 ~1ms 190 W: prolate 10 - isomer PES ground state PES 10 - (keV) [Walker and Xu, PLB636 (2006) 286]
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190 W with Gammasphere Lane et al., Phys. Rev. C82 (2010) 051304
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190 W with Gammasphere Lane et al., Phys. Rev. C82 (2010) 051304 10 - isomer at 1839 keV
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isomer energies, potential energy surfaces 190 Os 114 192 Os 116 190 W 116 (calc) (exp) 0+0+ 10 - 1633 2360±25 2015 6s 1920 1705 10m 1700 ~1ms 190 W: prolate 10 - isomer PES ground state PES 10 - (keV) 1839 240µs [Walker and Xu, PLB636 (2006) 286]
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190 W with Gammasphere Lane et al., Phys. Rev. C82 (2010) 051304 That was the high-K isomer. What about the oblate rotation?
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190 W with Gammasphere Lane et al., Phys. Rev. C82 (2010) 051304 That was the high-K isomer. What about the oblate rotation? (12 + ) yrast at 2653 keV
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190 W TRS: prolate to oblate ħω = 0.216 MeVħω = 0.200 MeV I = 4 prolate I = 14 oblate rotation alignment of 2 i 13/2 neutrons with oblate shape γ=0 o γ=-60 o [Walker and Xu, PLB636 (2006) 286]
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N=116 74 W 76 Os 78 Pt 80 Hg 0+0+ 2+2+ (i 13/2 ) 2 12 + 2653 207206 2451 412 2439 329 9 ns 5 ns ? 200 ns 194 Pt and 196 Hg: Levon et al., Nucl. Phys. A764 (2006) 24 experimental energies, spins and half-lives 190 W Lane et al. 192 Os: Valiente-Dobon et al., Phys. Rev. C69 (2004) 024316
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projected shell model (angular momentum basis) Sun et al., PLB659 (2008) 165
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summary - oblate-prolate competition in N = 116 188 Hf – 190 W – 192 Os - N = 116 seems to be the critical-point neutron number - focus on angular momentum effects - 10 - prolate K isomers - 12 + isomers: bandheads of collective oblate bands?? - giant backbending candidates: cf. Hilton and Mang 1979 - oblate rotation becomes yrast over a wide spin range - more data needed!! ( 188 Hf, 190 W and/or 192 Os)
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