Nuclear masses, deformations and shell effects

TL;DR

This study demonstrates that the Liquid Drop Model more accurately predicts the masses of prolate deformed nuclei than spherical ones, especially when shell effects are included, highlighting deformation-dependent nuclear mass modeling.

Contribution

The paper compares three Liquid Drop Mass formulas across different nuclear deformation groups, revealing deformation-dependent accuracy and the importance of shell effects in nuclear mass predictions.

Findings

Liquid Drop Model fits prolate nuclei with RMS < 750 keV

Fits for spherical nuclei have RMS > 2000 keV

Including shell effects improves mass predictions in deformed nuclei

Abstract

We show that the Liquid Drop Model is best suited to describe the masses of prolate deformed nuclei than of spherical nuclei. To this end three Liquid Drop Mass formulas are employed to describe nuclear masses of eight sets of nuclei with similar quadrupole deformations. It is shown that they are able to fit the measured masses of prolate deformed nuclei with an RMS smaller than 750 keV, while for the spherical nuclei the RMS is, in the three cases, larger than 2000 keV. The RMS of the best fit of the masses of semi-magic nuclei is also larger than 2000 keV. The parameters of the three models are studied, showing that the surface symmetry term is the one which varies the most from one group of nuclei to another. In one model, isospin dependent terms are also found to exhibit strong changes. The inclusion of shell effects allows for better fits, which continue to be better in the prolate deformed nuclei region