Shell gaps and pn pairing interaction in N = Z nuclei

TL;DR

This paper investigates the factors influencing shell gaps in N=Z nuclei, highlighting the roles of single-particle levels, like-nucleon pairing, and proton-neutron pairing, and compares theoretical calculations with observed data.

Contribution

It demonstrates that shell gaps can be accurately described by combining single-particle level spacings with pairing interactions, emphasizing the importance of pn pairing in non-closed shell nuclei.

Findings

Shell gaps are explained by single-particle levels and pairing interactions.

Proton-neutron pairing is crucial for non-closed shell N=Z nuclei.

Calculated level spacings align with observed shell gaps after pairing subtraction.

Abstract

We analyze the observed shell gaps in N=Z nuclei determined from the binding energy differences. It is found that the shell gaps can be described by the combined contributions from the single-particle level spacing, the like-nucleon pairing, and the proton-neutron pairing interaction. This conclusion is consistent with that of Chasman in Phys. Rev. Lett. 99 (2007) 082501. For the double-closed shell N=Z nuclei, the single-particle level spacings calculated with Woods-Saxon potential are very close to those obtained by subtracting the nn pairing interaction from the observed shell gap. For the sub-closed or non-closed shell N=Z nuclei, the pn pairing interaction is shown to be important for the observed shell gaps.