Evolution of single-particle structure of silicon isotopes

TL;DR

This paper provides new experimental data and analysis on the evolution of single-particle energies and shell structure in silicon isotopes, revealing persistent and emerging magic numbers and density distribution changes.

Contribution

It offers the first comprehensive evaluation of proton and neutron single-particle energies and occupation probabilities in Si isotopes from N=12 to 28, highlighting shell evolution and density structure.

Findings

Persistence of Z=14 subshell closure with increasing N

Identification of N=16 as a new magic number

Predicted weakening of N=28 shell closure and bubble-like proton density in neutron-rich isotopes

Abstract

New data on proton and neutron single-particle energies $E_{nlj}$ of Si isotopes with neutron number $N$ from 12 to 28 as well as occupation probabilities $N_{nlj}$ of single particle states of stable isotopes $^{28,30}$Si near the Fermi energy were obtained by the joint evaluation of the stripping and pick-up reaction data and excited state decay schemes of neighboring nuclei. The evaluated data indicate following features of single-particle structure evolution: persistence of $Z = 14$ subshell closure with $N$ increase, the new magicity of the number $N = 16$, and the conservation of the magic properties of the number $N = 20$ in Si isotopic chain. The features were described by the dispersive optical model. The calculation also predicts the weakening of $N = 28$ shell closure and demonstrates evolution of bubble-like structure of the proton density distributions in neutron-rich Si isotopes.