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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.
Abstract

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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