Probing the Z = 6 spin-orbit shell gap with (p,2p) quasi-free scattering reactions

TL;DR

This study investigates the Z=6 spin-orbit shell gap in exotic carbon isotopes using (p,2p) reactions, providing insights into shell evolution and challenging the idea of a strong magic number at Z=6 near the neutron dripline.

Contribution

It employs quasi-free scattering reactions to measure the proton component of excited states, revealing a moderate reduction in spin-orbit splitting contrary to previous claims.

Findings

Supports a moderate reduction of the proton 1p spin-orbit splitting

Challenges the notion of a strong Z=6 magic number near the neutron dripline

Provides spectroscopic data on carbon isotopes approaching the dripline

Abstract

The evolution of the traditional nuclear magic numbers away from the valley of stability is an active field of research. Experimental efforts focus on providing key spectroscopic information that will shed light into the structure of exotic nuclei and understanding the driving mechanism behind the shell evolution. In this work, we investigate the Z = 6 spin-orbit shell gap towards the neutron dripline. To do so, we employed $^{A}$N(p,2p)$^{A-1}$C quasi-free scattering reactions to measure the proton component of the 2$^+_1$ state of $^{16,18,20}$C. The experimental findings support the notion of a moderate reduction of the proton 1p$_{1/2}$-1p$_{3/2}$ spin-orbit splitting, at variance to recent claims for a prevalent Z = 6 magic number towards the neutron dripline.