Shell structure from nuclear observables

TL;DR

This paper extends a structural analysis method to protons and neutrons, using various experimental observables to identify shell structures in nuclei, revealing complex features and inconsistencies especially in low-mass nuclei.

Contribution

It introduces an extended approach analyzing both protons and neutrons using multiple observables to better understand nuclear shell structures.

Findings

Shell structures are identified through extrema in experimental observables.

Multiple shell features are observed in midshell regions.

Inconsistencies in shell structure are found in low-mass nuclei.

Abstract

The appearance and disappearance of shells and subshells are determined using a previously introduced method of structural analysis. This work extends the approach and applies it to protons, in addition to neutrons, in an attempt to provide a more complete understanding of shell structure in nuclei. Experimental observables including the mean-square charge radius, as well as other spectroscopic and mass related quantities are analyzed for extrema. This analysis also uses differential observables among adjacent even-even nuclei to serve as the derivatives for these quantities of interest. Local extrema in these quantities indicate shell structure and the lack of local extrema indicate missing shell closures. The shell structure of low-mass nuclei is inconsistent likely as a consequence of the single-particle structure. Additionally, multiple shell features occurring in midshell regions are determined by combining information from two or more observables. Our results near stability complement previous observations further out.