Shape and multiple shape coexistence of nuclei within covariant density functional theory

TL;DR

This study uses covariant density functional theory to systematically analyze shape coexistence in nuclei across the nuclear chart, predicting regions of shape coexistence and linking it to $E0$ transition strengths.

Contribution

It introduces a comprehensive method to predict shape coexistence in nuclei using covariant density functional theory and quadrupole shape invariants, extending understanding especially in neutron-rich regions.

Findings

Good agreement with experimental spectra

Predicted numerous nuclei with shape coexistence in neutron-rich areas

Strong $E0$ transitions often indicate shape coexistence

Abstract

Shape and multiple shape coexistence of nuclei are investigated throughout the nuclear chart by calculating the low-lying spectra and the quadrupole shape invariants for even-even nuclei with $10\leq Z\leq 104$ from the proton drip line to the neutron one within a five-dimensional collective Hamiltonian based on the covariant density functional PC-PK1. The quadrupole shape invariants are implemented to characterize the quadrupole deformations of low-lying $0^+$ states and predict nuclear mass regions of shape and multiple shape coexistence. The predicted low-lying spectra and the shape or multi-shape coexisting nuclei are overall in good agreement with the available experimental results. In addition, the present work predicts a wealth of nuclei with shape or multiple shape coexistence in the neutron-rich regions. The connection between the strong $E0$ transition strength and the occurrence of shape coexistence is analyzed systemically. It is found that nuclei with pronounced shape coexistence generally have strong $E0$ transition strengths, while the reverse may not be true. The present results can serve as useful guidelines for experimental searches and theoretical studies of shape and multiple shape coexistence, especially in neutron-rich regions.