Effect of Finite Binding on the Apparent Spin-Orbit Splitting in Nuclei

TL;DR

This paper investigates how finite binding effects influence the apparent spin-orbit splitting in nuclei, particularly explaining observed changes in neutron orbital separations in calcium isotopes without invoking exotic proton structures.

Contribution

It demonstrates that finite binding effects near zero energy primarily account for the observed changes in neutron spin-orbit splitting, challenging previous interpretations involving proton bubbles.

Findings

Finite binding effects significantly influence neutron orbital energies.

Observed neutron orbital separation changes are mainly due to near-zero binding energies.

Results reduce the need to invoke proton bubble structures to explain data.

Abstract

The apparent splitting between orbitals that are spin-orbit partners can be substantially influenced by the effects of finite binding. In particular, such effects can account for the observed decrease in separation of the neutron $1p_{3/2}$ and $1p_{1/2}$ orbitals between the $^{41}$Ca and $^{35}$Si isotopes. This behavior has been the subject of recent experimental and theoretical works and cited as evidence for a proton "bubble" in $^{34}$Si causing an explicit weakening of the spin-orbit interaction. The results reported here suggest that the change in the separation between the $1p_{3/2}$ and $1p_{1/2}$ partners occurs dominantly because of the behavior of the energies of these $1p$ neutron states near zero binding.