Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in (254)Rf

Abstract : Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) mu s 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-pi = 8(-), nu(2)(7/2(+)[624]; 9/2(-)[734]) two-quasineutron and the K-pi = 16(+), 8(-)nu(2)(7/2(+)[624]; 9/2(-)[734] circle times 8(-)pi(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) mu s. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.
Keywords : NUCLEI STATES FM-250 NO-254
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Journal articles
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Submitted on : Thursday, October 22, 2015 - 3:33:11 PM
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H M. David, Jie Chen, D. Seweryniak, F G. Kondev, J M. Gates, et al.. Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in (254)Rf. Physical Review Letters, American Physical Society, 2015, 115 (issue 13), pp.132502. ⟨10.1103/PhysRevLett.115.132502⟩. ⟨in2p3-01219383⟩

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