Quantum and Coulomb repulsion effects on the bubble structures in $^{204, 206}$Hg

TL;DR

This study investigates the bubble-like proton and charge density structures in $^{204, 206}$Hg using covariant density functional theory, revealing quantum effects and Coulomb repulsion contributions to central density depressions.

Contribution

It provides a detailed analysis of bubble structures in mercury isotopes considering dynamic correlations and Coulomb effects, advancing understanding of nuclear density distributions.

Findings

Charge-density difference between $^{208}$Pb and $^{204}$Hg is improved.

Central depression persists when symmetry restoration and shape mixing are included.

Bubble structures are mainly due to quantum effects inside 2.0 fm and Coulomb repulsion beyond 2.0 fm.

Abstract

The decreasing proton and charge densities from around 5.0 fm towards the center of $^{204, 206}$Hg are investigated by a covariant density functional theory at the beyond mean-field level.The charge-density difference between $^{208}$Pb and $^{204}$Hg is improved significantly and a central depression is still visible in the ground-state density of $^{204, 206}$Hg when the dynamic correlations associated with symmetry restoration and shape mixing are taken into account. For the $0_2^+$ and $2_1^+$ excited states of $^{204, 206}$Hg, their densities remain decreasing from 5.0 fm to around 2.0 fm, but become flat in the interior region. The results show that the bubble structure in $^{204, 206}$Hg within 2.0 fm is mainly attributed to the quantum effect, while that beyond 2.0 fm is formed by the Coulomb repulsion.