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

F. G. Kondev; G. D. Dracoulis; G. J. Lane; I. Ahmad; A. P. Byrne; M. P. Carpenter; P. Chowdhury; S. J. Freeman; N. J. Hammond; R. V. F. Janssens; T. Kibédi; T. Lauritsen; C. J. Lister; G. Mukherjee; D. Seweryniak; S. K. Tandel

doi:10.1140/epja/i2004-10025-9

2021 Impact factor 3.131

Hadrons and Nuclei

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

F. G. Kondev¹^*, G. D. Dracoulis², G. J. Lane², I. Ahmad³, A. P. Byrne²^,4, M. P. Carpenter³, P. Chowdhury⁵, S. J. Freeman³, N. J. Hammond³, R. V. F. Janssens³, T. Kibédi², T. Lauritsen³, C. J. Lister³, G. Mukherjee³^,5, D. Seweryniak³ and S. K. Tandel⁵

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.