Multi-quasiparticle high-K isomeric states in deformed nuclei

F R Xu,Y Shi,W Y Liang,G D Dracoulis,P M Walker,H L Liu,M.W Reed,E.C Simpson,A.J Mitchell

doi:10.1051/epjconf/201612301002

Abstract

In the past years, we have made many theoretical investigations on multi-quasiparticle high- K isomeric states. A deformation-pairing-configuration self-consistent calculation has been developed by calculating a configuration-constrained multi-quasiparticle potential energy surface (PES). The specific single-particle orbits that define the high- K configuration are identified and tracked (adiabatically blocked) by calculating the average Nilsson numbers. The deformed Woods-Saxon potential was taken to give single-particle orbits. The configuration-constrained PES takes into account the shape polarization effect. Such calculations give good results on excitation energies, deformations and other structure information about multi-quasiparticle high- K isomeric states. Many different mass regions have been investigated.

Highlights

Atomic nuclei can be excited by breaking paired nucleons [1,2,3,4]
Previous calculations were usually performed assuming that isomers have the same deformation as the ground state of the nucleus
High-Ω orbits (Ω is defined as the nucleon angular momentum projection onto the symmetry axis of the deformed nucleus) usually have a strong deformation-driving force, that would make the isomer shape deviate from that of the ground state

Summary

Introduction

If the unpaired nucleons couple to a high angular momentum (usually resulting in a large angular momentum projection onto the symmetry axis of the deformed nucleus, named K), the excited state can be an isomer due to the forbiddenness of electromagnetic decays from highK to low-K states [1, 2]. High-Ω orbits (Ω is defined as the nucleon angular momentum projection onto the symmetry axis of the deformed nucleus) usually have a strong deformation-driving force, that would make the isomer shape deviate from that of the ground state. The quadrupole pairing can be included [17] but its effect on the excitation energies of multi-quasiparticle states is small [18].

Calculations

Summary