Spin-aligned neutron-proton pair coupling in the era of large scale computing

Abstract

Shell model calculations reveal that the ground and low-lying yrast states of the N = Z nuclei 9246Pd and 9648Cd are mainly built upon isoscalar spin-aligned neutron-proton pairs each carrying the maximum angular momentum J = 9 allowed by the shell 0g9/2 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. It may help in understanding the intrinsic structure of the shell-model wave function. In particular, we will explore the competition between the normal monopole pair coupling and the spin-aligned coupling schemes.