Spherical to deformed shape transition in the nucleon-pair shell model

TL;DR

This paper investigates the shape transition from spherical to deformed nuclei in Ce isotopes using the nucleon-pair shell model, highlighting its ability to model the transition but also its limitations in transition smoothness.

Contribution

It introduces a microscopic framework for the nucleon-pair approximation that captures shape transitions in nuclei, emphasizing the importance of collective pair structures.

Findings

The model successfully produces a shape transition in Ce isotopes.

The transition occurs too rapidly compared to experimental observations.

Maintaining multiple pairs with each angular momentum may improve the model.

Abstract

A study of the shape transition from spherical to axially deformed nuclei in the even Ce isotopes using the nucleon-pair approximation of the shell model is reported. As long as the structure of the dominant collective pairs is determined using a microscopic framework appropriate to deformed nuclei, the model is able to produce a shape transition. However, the resulting transition is too rapid, with nuclei that should be transitional being fairly well deformed, perhaps reflecting the need to maintain several pairs with each angular momentum.