Bubble nuclei with shape coexistence in even-even isotopes of Hf to Hg

TL;DR

This study systematically investigates bubble nuclei with shape coexistence in certain isotopes using relativistic Hartree-Bogoliubov theory, revealing how deformation and pairing affect bubble structures and predicting candidate isotopes with both features.

Contribution

It is the first comprehensive analysis combining bubble nuclei and shape coexistence in these isotopes using advanced relativistic mean-field models.

Findings

Deformations and pairing correlations hinder bubble structures.

Certain isotopes, like $^{206}$Os, exhibit bubble structures in multiple deformations.

Depletion fraction varies with shape, being smaller in oblate deformations.

Abstract

The shape of a nucleus is one of fundamental nuclear properties. We perform a systematic investigation of bubble nuclei that also exhibit shape coexistence in Hf, W, Os, Pt and Hg even-even isotopes using the deformed relativistic Hartree-Bogoliubov theory in continuum. For a systematic study, we first consider nuclear bubble structures and shape coexistence separately. We confirm that deformations and pairing correlations hinder bubble structures by comparing our results with those from relativistic continuum Hartree-Bogoliubov theory that assumes spherical symmetry in nuclei. We then predict candidate isotopes with both bubble structure and shape coexistence. We observe that the depletion fraction factor that characterizes bubble structure is mostly smaller in oblate deformation than in prolate, while some isotopes such as $^{206}$Os have bubble structures both in oblate and prolate deformations. We compare the proton single-particle energy levels for the candidates of shape coexistence both with only prolate bubble structure and with prolate and oblate bubble structures.