Rotational and intrinsic states above the Kπ=25/2,T1/2=25 day isomer in 179Hf

S. M. Mullins, G. D. Dracoulis, A. P. Byrne, T. R. McGoram, S. Bayer, R. A. Bark, R. T. Newman, W. A. Seale, and F. G. Kondev
Phys. Rev. C 61, 044315 – Published 10 March 2000
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Abstract

Time-correlated, particle-tagged γ spectroscopy of the stable nucleus 179Hf was undertaken with incomplete fusion reactions initiated by beams of 9Be and 7Li incident on targets of 176Yb. Intrinsic and rotational states above the three-quasiparticle Kπ=25/2,T1/2=25day isomer, 179Hfm2, are reported. The rotational band based on 179Hfm2 has gKgR values that are consistent with the previously suggested ν9/2+π2[7/2+,9/2] configuration assignment. A value of gR=0.34(5) was derived for the collective g factor of 179Hfm2, which is considerably higher than that found for the 9/2+ ground state. The difference is consistent with a reduction of the proton pairing strength due to blocking in the Kπ=25/2νπ2 configuration. A number of ν3π2 five-quasiparticle configurations were identified, the highest of which is an yrast Kπ=43/2+,T1/2=15(5)μs isomer. It decays to an yrast Kπ=39/2 state, which in turn decays to a rotational band based on a Kπ=33/2 state. The Kπ=33/2 state decays to the rotational band associated with 179Hfm2. Semiempirical calculations reproduce the excitation energies of the three- and five-quasiparticle states above 179Hfm2 to within 200keV. The calculations predict that the lowest seven-quasiparticle state will arise from a ν5π2 configuration with Kπ=47/2, which is just beyond the maximum spin accessible with the reactions employed here.

  • Received 29 October 1999

DOI:https://doi.org/10.1103/PhysRevC.61.044315

©2000 American Physical Society

Authors & Affiliations

S. M. Mullins, G. D. Dracoulis, A. P. Byrne*, T. R. McGoram, S. Bayer, R. A. Bark, R. T. Newman, W. A. Seale, and F. G. Kondev§

  • Department of Nuclear Physics, RSPhysSE, The Australian National University, Canberra, ACT 0200, Australia

  • *Joint appointment with the Department of Physics, The Faculties, The Australian National University, Canberra, ACT 0200, Australia.
  • Permanent address: National Accelerator Center, Faure, South Africa.
  • Permanent address: Laboratório Pelletron, Departamento de Física Nuclear, Instituto de Física, Universidade de São Paulo, São Paulo, Brazil.
  • §Present address: Argonne National Laboratory, Argonne, IL 60439.

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Vol. 61, Iss. 4 — April 2000

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