# Shape and shell-structure of lighter (N<90) neutron-rich nuclei based on phenomenological Woods-Saxon potential

## TL;DR

This paper investigates the shape and shell structure of neutron-rich nuclei near the drip line and the r-process using a Woods-Saxon potential, revealing insights into halo formation and the N=40 island of inversion.

## Contribution

It provides a systematic analysis of shell structures in weakly-bound neutrons and compares them across different nuclei, highlighting differences from stable nuclei and the nature of the N=40 island of inversion.

## Key findings

- Identification of neutron numbers where halos may form.
- Differences in shell structure between r-process and stable nuclei.
- N=40 island of inversion in Fe and Cr isotopes is unlikely to persist up to N=50.

## Abstract

By using a phenomenologically successful Woods-Saxon potential, I study the shape and shell structure of (A) neutron drip line nuclei with 10 \leq N \leq 60, (B) neutron-rich nuclei related to the r- process with 40 \leq N \leq 90, and (C) one-particle spectra in the potential provided by the nucleus 70Fe as a representative of so-called N=40 "island of inversion (IoI)" nuclei. First, the shell structure that is unique in very weakly-bound neutrons is systematically studied, and the approximate neutron number of odd-N nuclei at which spherical (or deformed) halos can be found is pinned down. Second, the difference of the shell structure in r-process nuclei from that in stable nuclei is examined. Third, the similarity and the difference between the shell structure of N=20 IoI nuclei and that of N=40 IoI nuclei are analyzed. As a result of it, it is concluded that in Fe and Cr isotopes the deformation called "N=40 IoI" continuing up to N=50 is unlikely.