Search for a 2-quasiparticle high-K isomer in Rf256

A. P. Robinson, T. L. Khoo, D. Seweryniak, I. Ahmad, M. Asai, B. B. Back, M. P. Carpenter, P. Chowdhury, C. N. Davids, J. Greene, P. T. Greenlees, K. Hauschild, A. Heinz, R. D. Herzberg, R. V.F. Janssens, D. G. Jenkins, G. D. Jones, S. Ketelhut, F. G. Kondev, T. LauritsenC. J. Lister, A. Lopez-Martens, P. Marley, E. McCutchan, P. Papadakis, D. Peterson, J. Qian, D. Rostron, U. Shirwadkar, I. Stefanescu, S. K. Tandel, X. Wang, S. Zhu

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29 Citations (Scopus)


The energies of 2-quasiparticle (2-qp) states in heavy shell-stabilized nuclei provide information on the single-particle states that are responsible for the stability of superheavy nuclei. We have calculated the energies of 2-qp states in Rf256, which suggest that a long-lived, low-energy 8- isomer should exist. A search was conducted for this isomer through a calorimetric conversion electron signal, sandwiched in time between implantation of a Rf256 nucleus and its fission decay, all within the same pixel of a double-sided Si strip detector. A 17(5)-μs isomer was identified. However, its low population, ~5(2)% that of the ground state instead of the expected ~30%, suggests that it is more likely a 4-qp isomer. Possible reasons for the absence of an electromagnetic signature of a 2-qp isomer decay are discussed. These include the favored possibility that the isomer decays by fission, with a half-life indistinguishably close to that of the ground state. Another possibility, that there is no 2-qp isomer at all, would imply an abrupt termination of axially symmetric deformed shapes at Z=104, which describes nuclei with Z=92-103 very well.

Original languageEnglish
Article number064311
JournalPhysical Review C - Nuclear Physics
Issue number6
Publication statusPublished - Jun 15 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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