Systematic shell-model study on spectroscopic properties in the south region of $^{208}$Pb

TL;DR

This study systematically investigates nuclei near $^{208}$Pb using shell-model calculations, accurately predicting properties and exploring the robustness of the $N=126$ shell closure, with a new Hamiltonian developed for this region.

Contribution

A new shell-model Hamiltonian was constructed and validated, enabling precise predictions of nuclear properties in the south region of $^{208}$Pb, including unknown isomeric states.

Findings

Shell-model results match experimental binding and spectroscopic data.

Predicted isomeric states in neutron-rich Pb, Tl, and Hg isotopes.

Validated the robustness of the $N=126$ shell closure.

Abstract

We aim to study the properties of nuclei in the south region of $^{208}$Pb systematically, including the binding and excitation energies and electromagnetic properties, in order to predict unknown properties of these nuclei, such as isomerism, utilizing a theoretical model which describes the experimentally known properties precisely. We also address whether the $N=126$ shell closure is robust or not when the proton number decreases from $^{208}$Pb. We performed large-scale shell-model calculations with a new Hamiltonian suggested in the present work. The model space is taken as the five proton orbits within $50<Z\leqslant82$ and the thirteen neutron orbits within $82<N\leqslant184$. And one-particle one-hole excitation is allowed across the $N=126$ gap. The Hamiltonian is constructed by combining the existing Hamiltonians, KHHE (with adjustment of its proton-proton part) and KHPE, and the monopole based universal interaction. The shell-model results well reproduce the experimentally observed binding energies and spectroscopic properties, such as isomerism, core excitation, and electromagnetic properties. Some possible isomeric states in neutron-rich Pb, Tl, and Hg isotopes are predicted with transition energies and half-lives. We also examine the effective charges and the quenching of the $g$ factors suitable for this region by systematic comparisons between observed and calculated electromagnetic properties. A new Hamiltonian is constructed for nuclei in the south region of $^{208}$Pb, mainly including Pb, Tl, Hg, Au, Pt, Ir, Os, Re, and W isotopes around $N=126$, and provides them reasonable descriptions on nuclear properties including binding energies, excitation energies and electromagnetic properties through comprehensive and systematic studies.