Nuclear shapes: Quest for triaxiality in 86Ge and the shape of 98Zr

V Werner,A Obertelli,C.-Y Wu,W Witt,C Lizarazo,M Carpenter,N Pietralla,P Doornenbal,S Zhu,P.-A Söderström,M Lettmann,G Savard,D Cline

doi:10.1051/epjconf/201817802013

Abstract

The region of neutron-rich nuclei above the N = 50 magic neutron shell closure encompasses a rich variety of nuclear structure, especially shapeevolutionary phenomena. This can be attributed to the complexity of sub-shell closures, their appearance and disappearance in the region, such as the N = 56 sub shell or Z = 40 for protons. Structural effects reach from a shape phase transition in the Zr isotopes, over shape coexistence between spherical, prolate, and oblate shapes, to possibly rigid triaxial deformation. Recent experiments in this region and their main physics viewpoints are summarized.

Highlights

IntroductionAmong the consequences of these sphericity-driving sub shells is a stabilization of spherical shapes in the ground states of the respective nuclei, and a fast transition toward deformation in the Zr isotopic chain as the sub-shell closures disappear due to changes in the ordering of effective single-particle energies and the early filling of higher-lying orbitals
The mass A ≈ 100 region above N = 50 is a region of the nuclear chart which is dominated by the occurrence of multiple major and sub-shell closures
Among the consequences of these sphericity-driving sub shells is a stabilization of spherical shapes in the ground states of the respective nuclei, and a fast transition toward deformation in the Zr isotopic chain as the sub-shell closures disappear due to changes in the ordering of effective single-particle energies and the early filling of higher-lying orbitals

Summary

Introduction

Among the consequences of these sphericity-driving sub shells is a stabilization of spherical shapes in the ground states of the respective nuclei, and a fast transition toward deformation in the Zr isotopic chain as the sub-shell closures disappear due to changes in the ordering of effective single-particle energies and the early filling of higher-lying orbitals. It is, still an open question at what mass number in the Zr isotopic chain the phase transition from a spherical to a deformed ground-state structure occurs. Two protons below the Se isotopes, namely, in 86Ge, we identify 86Ge as a candidate for displaying rigid ground-state triaxiality [5], a rare phenomenon which has, so far in medium-heavy nuclei, only been observed in its lighter isotope, 76Ge [6]

Triaxial 86Ge?

The critical-point isotope 98Zr

Summary