Competition of different coupling schemes in atomic nuclei

TL;DR

This paper investigates how spin-aligned neutron-proton pairs influence the structure of certain N=Z nuclei, highlighting their dominance in low-lying states and their importance as fundamental building blocks in nuclear models.

Contribution

It introduces the significance of spin-aligned neutron-proton pairs in nuclear structure, emphasizing their role over traditional monopole pairing in specific nuclei.

Findings

Spin-aligned neutron-proton pairs dominate low-lying states in $^{92}$Pd and $^{96}$Cd.

The coupling scheme differs from conventional monopole pairing.

This mode provides new insights into N=Z nuclear structure.

Abstract

Shell model calculations reveal that the ground and low-lying yrast states of the $N=Z$ nuclei $^{92}_{46}$Pd and $^{96}$Cd are mainly built upon isoscalar spin-aligned neutron-proton pairs each carrying the maximum angular momentum J=9 allowed by the shell $0g_{9/2}$ which is dominant in this nuclear region. This mode of excitation is unique in nuclei and indicates that the spin-aligned pair has to be considered as an essential building block in nuclear structure calculations. In this contribution we will discuss this neutron-proton pair coupling scheme in detail. In particular, we will explore the competition between the normal monopole pair coupling and the spin-aligned coupling schemes. Such a coupling may be useful in elucidating the structure properties of $N=Z$ and neighboring nuclei.