Properties of neutron-rich hafnium high-spin isomers: P-325 P.M. Walker1,2, P.H. Regan1, Z. Podolyak1, M.W. Reed1, R.T. Wood1, M. Kowalska2, K.T. Flanagan3, J. Billowes3, B. Cheal3, D.H. Forest4, G. Tungate4, G. Neyens5, M.L. Bissell5, U. Köster6, Y. Litvinov7, C. Kozhuharov7, B. Blank8, P. Delahaye9, G.D. Dracoulis10   1 University of Surrey, UK 2 CERN, Geneva, Switzerland 3 University of Manchester, UK 4 University of Birmingham, UK 5 University of Leuven, Belgium 6 ILL, Grenoble, France 7 GSI, Darmstadt, Germany 8 CENBG, Bordeaux, France 9 GANIL, Caen, France 10ANU, Canberra, Australia

physics motivation Upper part of shell (N=82-126, Z=50-82). Reinforcing proton and neutron effects. Prolate-to-oblate phase transition (I=0). Prolate “deformation-aligned” high-K states vs. oblate rotation-aligned (I=10-20). Access gained through isomer decays. Isomer half-lives reflect underlying physics (e.g. level-density effect on K mixing).

prolate-oblate shape transition n-rich hafnium ground states HFB + SLy4 60 γ 30 Here calculated ground-state shapes are shown (part of a much wider range of calculated shapes). The delicate balance in 188Hf between prolate and oblate shapes is evident. It is important also to consider the effects of angular momentum – see later slide. Robledo et al., J. Phys. G: Nucl. Part. Phys. 36, 115104 (2009).

Nilsson single-particle diagram N = 116 Fermi level (188Hf) Here we illustrate the prolate (high-K) and oblate (low-K) Fermi levels for neutrons. The situation is similar for protons, though in a different shell. The proton and neutron shells are each 2/3 filled. prolate oblate

Nilsson single-particle diagram N = 116 Fermi level (188Hf) and similarly for protons Here we illustrate the prolate (high-K) and oblate (low-K) Fermi levels for neutrons. The situation is similar for protons, though in a different shell. The proton and neutron shells are each 2/3 filled. prolate oblate

prolate-oblate shape transition 182Hf 186Hf oblate rotation prolate rotation prolate K states configuration constrained TRS calculations Xu, Walker and Wyss, Phys. Rev. C62 (2000) 014301

Nuclear chart with isomers Z=72 (Hf) A~190 [Walker and Dracoulis, Nature 399 (1999) 35, updated]

hafnium (Z=72) 4-quasiparticle isomers 178Hf 188Hf expt. calc. predictions Walker and Dracoulis, Nature 399 (1999) 35; Hyp. Int. 135 (2001) 83

hafnium (Z=72) 4-quasiparticle isomers 178Hf 188Hf expt. calc. X (15) 12m Reed et al. 2010 184Hf predictions Walker and Dracoulis, Nature 399 (1999) 35; Hyp. Int. 135 (2001) 83

isomers in the storage ring at GSI 10-second snapshots 197Au fragmentation A = 184, q = 72+ 0e 1e m2 g Ta bare Hf 2.5 MeV time (minutes) 10 2.5 MeV A = 184, q = 72+ 20 frequency Reed et al., Phys. Rev. Lett. 105 (2010) 172501

197Au fragmentation at GSI beam We used a 197Au beam, and found new, long-lived isomers in 186Ta, 187Ta, 183Hf, 184Hf and (tentatively) in 186Hf. new isomers T1/2 >10 s Reed et al., Phys. Rev. Lett. 105 (2010) 172501

W and Ir spallation at ISOLDE this proposal target nuclides isomers to study

IS-537 experiment => isomer half-lives β decays γ decays 184Hf 3 shifts 183Hf 3 shifts setting up 3 shifts Total beam time: 9 shifts ISOLDE tape transport ion beam => isomer half-lives β decays γ decays Ge Ge β-γ-γ coincidences

184Hf isomer data decay Eγ-spec EESR T1/2(exp) ground state (0+) β 4 h isomer 1 (8-) γ+β 1272(1)a 1264(10) 48 s isomer 2 (15+) β 2477(10) 12 min a Krumbholz et al., Z. Phys. A351 (1995) 11 keV keV new data Reed et al. PRL105 (2010) 172501 Hf 4-quasiparticle isomers new calculations Liu et al. Phys. Rev. C83 (2011) 067303