Structural properties of nuclei with semi-magic number N(Z)=40

TL;DR

This study investigates the structural properties of nuclei with neutron or proton number 40 using relativistic mean-field theory, confirming magicity in certain isotopes and revealing shape transitions and bubble nuclei phenomena.

Contribution

It provides a comprehensive analysis of N=40 isotonic and Z=40 isotopic chains, highlighting double magicity, shape coexistence, and the role of specific nuclear states with new theoretical insights.

Findings

N=40 isotonic chain supports neutron magicity and double magicity in 60Ca and 68Ni.

Zr isotopes exhibit shape transitions and coexistence.

Identified 56S and 122Zr as doubly bubble nuclei.

Abstract

Various ground state properties are explored for full isotonic(isotopic) chain of neutron number N(proton number Z)$=$40 using different families of Relativistic Mean-Field theory. Several properties such as nucleon separation energies, pairing energies, deformation, radii and nucleon density distributions are evaluated and compared with the experimental data as well as those from other microscopic and macroscopic models. N$=$40 isotonic chain presents ample of support for the neutron magicity and articulates double magicity in recently discovered $^{60}$Ca and $^{68}$Ni. Our results are in close conformity with recently measured value of charge radius of $^{68}$Ni [S. Kaufmann \textit{et al.}, Phys. Rev. Lett. 124, 132502 (2020)] which supports the N$=$40 magicity. Contrarily, Zr isotopes (Z$=$40) display variety of shapes leading to the phenomenon of shape transitions and shape co-existence. The role of 3s$_{1/2}$ state, which leads to central depletion if unoccupied, is also investigated. $^{56}_{16}$S and $^{122}_{40}$Zr are found to be doubly bubble nuclei.