Department of Mathematical Physics

Ingemar Ragnarsson

Termination of rotational bands: Disappearance of quantum many-body collectivity.

A.V. Afanasjev, D.B. Fossan, G.J. Lane and I. Ragnarsson

Abstract: One of the most interesting features of nuclei is the process by which specific configurations, manifest as collective rotational bands at intermediate spin values, gradually lose their collectivity and terminate in a non-collective state at the maximum spin which can be built within the configuration. Recent advances in both experiment and theory allow the study of this nuclear structure feature in detail. The bands, which show such a continuous transition from high collectivity to a pure particle-hole (terminating) state, are generally called terminating bands or to underline their continuous character, smooth terminating bands. The best examples of such bands known at present are in the neutron-deficient A = 110 mass region, where terminating configurations involving proton particle-hole excitations across the Z=50 gap can be observed over their entire spin range. The main features of band termination as a specific high-spin phenomenon inherent to finite many-fermion strongly interacting systems are overviewed, based mainly on the configuration-dependent cranked Nilsson-Strutinsky approach. The extensive experimental results on smooth terminating bands in the A = 110 mass region, which have been addressed by these theoretical calculations, are presented along with the theoretical comparisons in a systematic way. In addition, specific features of band termination in other parts of the periodic chart and other possible theoretical approaches are briefly reviewed.