Bubble Structure in Magic Nuclei

TL;DR

This paper investigates bubble nuclei characterized by central density depletion across the nuclear chart, predicting new bubble nuclei, and analyzing their structural origins and effects, including in superheavy elements and temperature influences.

Contribution

It provides a comprehensive study of bubble nuclei, predicting new instances, analyzing their structural causes, and exploring effects in superheavy nuclei and temperature dependence, which advances understanding of nuclear density distributions.

Findings

Central depletion correlates with shell structure and unoccupancy in s-orbitals.

Bubble effect in superheavy nuclei results from Coulomb and neutron-neutron interactions.

Temperature increases in $^{34}$Si reduce the bubble effect.

Abstract

The existence of bubble nuclei identified by the central depletion in nucleonic density is studied for the conventional magic N (Z) $=$ 8, 20, 28, 40, 50, 82, 126 isotones (isotopes) and recently speculated magic N $=$ 164, 184, 228 superheavy isotones. Many new bubble nuclei are predicted in all regions. Study of density profiles, form factor, single particle levels and depletion fraction (DF) across the periodic chart reveals that the central depletion is correlated to shell structure and occurs due to unoccupancy in s-orbit (2s, 3s, 4s) and inversion of (2s, 1d) and (3s, 1h) states in nuclei upto Z $\le$ 82. Bubble effect in superheavy region is a signature of the interplay between the Coulomb and nn-interaction and depletion fraction (DF) is found to increase with Z (Coulomb repulsion) and decrease with isospin. Our results are consistent with the available data. The occupancy in s-state in $^{34}$Si increases with temperature which appears to quench the bubble effect.