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Open Access Publications from the University of California

Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in ^{254}Rf.

  • Author(s): David, HM
  • Chen, J
  • Seweryniak, D
  • Kondev, FG
  • Gates, JM
  • Gregorich, KE
  • Ahmad, I
  • Albers, M
  • Alcorta, M
  • Back, BB
  • Baartman, B
  • Bertone, PF
  • Bernstein, LA
  • Campbell, CM
  • Carpenter, MP
  • Chiara, CJ
  • Clark, RM
  • Cromaz, M
  • Doherty, DT
  • Dracoulis, GD
  • Esker, NE
  • Fallon, P
  • Gothe, OR
  • Greene, JP
  • Greenlees, PT
  • Hartley, DJ
  • Hauschild, K
  • Hoffman, CR
  • Hota, SS
  • Janssens, RVF
  • Khoo, TL
  • Konki, J
  • Kwarsick, JT
  • Lauritsen, T
  • Macchiavelli, AO
  • Mudder, PR
  • Nair, C
  • Qiu, Y
  • Rissanen, J
  • Rogers, AM
  • Ruotsalainen, P
  • Savard, G
  • Stolze, S
  • Wiens, A
  • Zhu, S
  • et al.

Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) μs have been discovered in the heavy ^{254}Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K^{π}=8^{-}, ν^{2}(7/2^{+}[624],9/2^{-}[734]) two-quasineutron and the K^{π}=16^{+}, 8^{-}ν^{2}(7/2^{+}[624],9/2^{-}[734])⊗8^{-}π^{2}(7/2^{-}[514],9/2^{+}[624]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N=150 isotones. The four-quasiparticle isomer is longer lived than the ^{254}Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2(1.1) μs. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.

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