Nuclear Structure of the even-even Argon isotopes with a focus on magnetic moments

TL;DR

This study investigates the nuclear structure and magnetic moments of even-even Argon isotopes, emphasizing configuration mixing effects and comparing different shell model interactions to understand their evolution with neutron number.

Contribution

It provides a detailed analysis of configuration mixing in Argon isotopes using shell model calculations with multiple interactions, highlighting differences in nuclear collectivity.

Findings

$^{40}$Ar and $^{44}$Ar have identical spectra and magnetic moments in a limited model space.

Deviations from this equality indicate configuration mixing effects.

$^{44}$Ar exhibits increased collectivity compared to $^{40}$Ar.

Abstract

We study the role of configuration mixing in the heavier even-even isotopes of Argon. We begin by limiting the configurations of the even-even Ar isotopes to $(d_{3/2}^2)_{\pi}$ $(f_{7/2}^n)_{\nu}$. There, due to the particular location in this shell model space of $^{40}$Ar and $^{44}$Ar, we find that the spectra, B(E2)'s and magnetic moments of these two nuclei are identical. Any deviation from this equality is direct evidence of configuration mixing. In a larger shell model space there are significant differences between these two nuclei, with $^{44}$Ar being more collective. We also consider other even-even isotopes of Argon and study how their nuclear structure effects evolve with N. We compare in the full 0$\hbar \omega$ space $(sd)_{\pi}$ $(fp)_{\nu}$ the results of calculations with the WBT interaction and with the newer SDPF, denoted SDPF-U, interaction.