Eur. Phys. J. Spec. Top. (2024) 233: 893-902
https://doi.org/10.1140/epjs/s11734-024-01137-y

Regular Article

Shell-model description of nuclear isomers

Department of Physics and Astronomy and the Facility for Rare Isotope Beams, Michigan State University, 48824-1321, East Lansing, MI, USA

^a brown@frib.msu.edu

Received: 30 January 2024
Accepted: 29 February 2024
Published online: 25 March 2024

Abstract

I review the origins of gamma-decay isomers starting within a spherical shell-model basis. Some isomers can be directly connected to the attractive proton–neutron interaction that gives rise to low-lying aligned states with a large $J_{\text{min}}-J_{\text{max}}$ gap. These two-particle isomers give rise multi-particle configurations with large J-gaps. The attractive $T=1$ paring-type interactions between two protons or two neutron give rise to a close spacing between the high-lying states with $J_{\text{max}}$ and $J_{\text{max}}-2$. The multi-particle configurations obtained with a pairing-type interaction can be classified by the seniority quantum number. Seniority selection rules for reduced matrix elements provide another source for isomers. Isomers can also be traced to the j-gaps in the single-particle energies obtained by realistic single-particle potentials.