Eur. Phys. J. A (2004) 22: 23-27
https://doi.org/10.1140/epja/i2004-10025-9

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

¹ Nuclear Engineering Division, Argonne National Laboratory, IL 60439, Argonne, USA
² Department of Nuclear Physics, R.S.Phys.S.E, Australian National University, ACT 0200, Canberra, Australia
³ Physics Division, Argonne National Laboratory, IL 60439, Argonne, USA
⁴ Department of Physics, The Faculties, Australian National University, ACT 0200, Canberra, Australia
⁵ Department of Physics, University of Massachusetts, MA 01854, Lowell, USA

^* e-mail: kondev@anl.gov

Abstract

A seven-quasiparticle isomer with 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 (5/2 ⁺ [402], 7/2 ⁺ [404], (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.