Bubble structure in magic nuclei

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 ≤ 82. Bubble effect in superheavy region is a signature of the interplay between the Coulomb and nn-interaction where the 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 34Si increases with temperature which appears to quench the bubble effect. Keywords: Relativistic mean-field plus BCS approach, Bubble nuclei, Statistical theory for hot nuclei, Magic nuclei, Temperature effect on bubble