Suppression of isoscalar pairing

TL;DR

This paper investigates why isoscalar pairing is suppressed in most nuclei despite the strong nuclear attraction in that channel, attributing it to the effects of spin-orbit splitting on single-particle energies.

Contribution

It provides a semiquantitative explanation for the suppression of isoscalar pairing in nuclei, emphasizing the role of spin-orbit splitting on high-j orbitals.

Findings

Isoscalar pairing is suppressed in most nuclei due to spin-orbit effects.

The deuteron is an exception where isoscalar pairing is evident.

High-j orbitals at the Fermi surface are key to understanding pairing behavior.

Abstract

The short-range nuclear attraction is stronger in the isoscalar channel than in the isovector channel, as evidenced by the existence of the deuteron and not the dineutron. Nevertheless, apart from light N=Z nuclei, pairing is only seen in the isovector channel. This is explained by the effect of the strong spin-orbit splitting on the single-particle energies. A semiquantitative argument is presented treating the high-j orbitals at the Fermi surface as plane waves on a two-dimensional sheet.