Isomer building blocks and K-forbidden decays

Abstract

High-K isomers are long-lived excitations of deformed atomic nuclei. Their structure is built from broken nucleon pairs that generate high angular momentum, K, along the nuclear symmetry axis. The partial conservation of this quantity leads to strong inhibition of electromagnetic decay, and hence to isomerism. The present work examines the hindrance factors for a range of multipole orders, with a focus on highly K-forbidden E1 transitions from multi-quasiparticle isomers in the region of nuclei. Allowing for a general 104 inhibition of E1 transitions, there is good accord with other multipole orders. A key feature is that the inhibition declines for isomers that are more highly excited, relative to a rigid rotor of the same total angular momentum. Comparison is also made with K-forbidden E1 transitions in the quasicontinuum, and similar inhibition properties are found.