K-Mixing and fast decay of a seven-quasiparticle isomer in 179Ta

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A seven-quasiparticle isomer with \(K^{\pi} = (49 /2^ + )\) and T 1/2 = 53 ( + 3 -7) ns has been identified in 179Ta. By comparing its excitation energy with results from multi-quasiparticle calculations that include the effects of blocking and residual nucleon-nucleon interactions, the isomer is assigned the \(\pi^{3}\) (5/2 + [402], 7/2 + [404], \(9/2^{-}[514]) \otimes \nu^{4}\) (5/2-[512], 7/2-[514], 7/2-[503], 9/2 + [624]) configuration. The decay of this isomer is found to be unusually fast, a feature that is attributed to a mixing with a specific collective level. The interaction strength is found to be orders of magnitude lower than that observed between interacting collective levels.

Received: 7 March 2004, Revised: 3 May 2004, Published online: 5 October 2004


21.10.Re Collective levels - 21.10.Tg Lifetimes - 23.20.Lv Gamma transitions and level energies - 27.70. + q \(150 \leq A \leq 189\)

S.J. Freeman: Present address: Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
G . Mukherjee: Present address: Nuclear and Atomic Physics Division, Saha Institute of Nuclear Physics, Kolkata 700 064, India.
Communicated by W. Henning