The effect of nuclear deformation on level statistics

TL;DR

This paper investigates how nuclear deformation influences the statistical distribution of energy levels in even-even nuclei, revealing a complex relationship between deformation and nuclear chaos.

Contribution

It introduces a Bayesian method to quantify chaos in nuclear energy levels and links the chaoticity parameter to nuclear quadrupole deformation.

Findings

Chaoticity decreases with increasing nuclear deformation.

Strongly deformed nuclei tend to exhibit regular energy level patterns.

Oblate deformations are associated with more regular spectra.

Abstract

We analyze the nearest neighbor spacing distributions of low-lying 2+ levels of even-even nuclei. We grouped the nuclei into classes defined by the quadrupole deformation parameter (Beta2). We calculate the nearest neighbor spacing distributions for each class. Then, we determine the chaoticity parameter for each class with the help of the Bayesian inference method. We compare these distributions to a formula that describes the transition to chaos by varying a tuning parameter. This parameter appears to depend in a non-trivial way on the nuclear deformation, and takes small values indicating regularity in strongly deformed nuclei and especially in those having an oblate deformation.