Elucidating shell/subshell closure and the critical impact of isospin-asymmetry on barium isotopes using relativistic mean-field approach

Abstract

The aspect of structural evolution and the correlation of the properties of the ground state with the effective symmetry energy and its coefficients is examined for neutron-rich even-even isotopes of barium nuclei (Z = 56). The nuclear bulk properties such as binding energy, root-mean-square charge radius, quadrupole deformation, two neutron separation energy, and two neutron shell gaps are calculated using the axially deformed relativistic mean field formalism for nonlinear NL3^⁎ and density-dependent sets of DD-ME2 force parameters. The calculated results are further compared with the available experimental data and other theoretical models. The results of the bulk nuclear properties indicate N = 82 as a neutron shell closure near the neutron-rich side of the isotopic chain of Ba nuclei. Alternatively, a systematic analysis of isospin-dependent observables, such as the nuclear symmetry energy and its volume and surface components, is estimated along the isotopic chain, which is crucial for studying shell/subshell closure away from the β-stability line. This work incorporates two types of relativistic mean-field densities as inputs. Firstly, the spherical density using the NL3* and DD-ME2 parameter sets. Secondly, for comparison, the monopole component of the multipole expanded deformed density using the DD-ME2 parameter. From the isospin-dependent properties, we observe that both the spherical and monopole components of the deformed density follow a similar trend along the isotopic chain. The isospin-dependent quantities are in accordance with the nuclear bulk properties while verifying the traditional shell closure at N = 82 for the neutron-rich Ba nuclei. In addition, we noticed a significant peak near N = 58, indicating greater stability than its neighbouring nuclei. Consequently, this study provides a novel region of interest for isospin-based experimental and theoretical studies. Furthermore, the present investigation is quite relevant for understanding the role of isospin-asymmetry in the variation of nuclear properties, which is pivotal for elucidating the synthesis of exotic nuclei along the nuclear chart.