Isomers, nuclear structure and spectroscopy

Abstract

Isomers and their roles in discovery and as probes of nuclear structure are discussed, with a focus on neutron-rich nuclei in the mass 180–190 region. Long-lived, high-K isomers are predicted in the heavy hafnium nuclei for example, some of which should be accessible by projectile fragmentation and deep-inelastic reactions. Progress with these reactions in reaching a broad range of isotopes to the right of the stability line is summarized. Recent results for isomers in the iridium and osmium isotopes produced in deep-inelastic reactions and studied with time-correlated γ-ray spectroscopy are presented as examples. These studies venture into the border region where well-deformed prolate shapes give way to soft, transitional nuclei. Prolate, oblate and triaxial structures are predicted, but with shapes that depend sensitively on the multi-particle configurations. Dynamical effects such as rotation alignment also play a significant role and produce isomeric states. In some cases, very low-lying multi-quasiparticle intrinsic states are predicted but these are possibly missed with current approaches. The prospects for the identification and characterization of such exotic isomers using new storage ring techniques, that might also provide a window into exotic states populated in their subsequent decay are outlined, as is the potential for studies with beams of isomers themselves.