Quartetting in odd-odd self-conjugate nuclei

TL;DR

This paper introduces a formalism using collective quartets and pairs to describe odd-odd self-conjugate nuclei in the sd shell, demonstrating good agreement with experimental spectra and emphasizing the importance of quartetting in nuclear structure.

Contribution

It develops a novel quartet and pair-based formalism for odd-odd nuclei, extending previous even-even studies and highlighting the role of J>0 quartets.

Findings

Spectra agree well with shell model and experimental data.

Quartetting is confirmed as significant in N=Z nuclei.

J>0 quartets play a key role in odd-odd spectra.

Abstract

We provide a description of odd-odd self-conjugate nuclei in the sd shell in a formalism of collective quartets and pairs. Quartets are four-body structures carrying isospin T=0 while pairs can have either T=0 or T=1. Both quartets and pairs are labeled by the angular momentum J and they are chosen so as to describe the lowest states of 20Ne (quartets) and the lowest T=0 and T=1 states of 18F (pairs). We carry out configuration interaction calculations in spaces built by one quartet and one pair for 22Na and by two quartets and one pair for 26Al. The spectra that are generated are in good agreement with the shell model and experimental ones. These calculations confirm the relevance of quartetting in the structure of N=Z nuclei that had already emerged in previous studies of the even-even systems and highlight the role of J>0 quartets in the composition of the odd-odd spectra.