Updated systematics of intermediate-energy single-nucleon removal cross sections

TL;DR

This paper reviews and analyzes intermediate-energy single-nucleon removal reactions, updating systematics with new high-energy data, and confirms the robustness of the sudden approximation across different energy regimes.

Contribution

It provides an updated systematic analysis of single-nucleon removal cross sections, incorporating new high-energy measurements and reinforcing the validity of the reaction model assumptions.

Findings

$R_s$ ratios follow a consistent linear trend across energies.

New high-energy data support earlier systematics without breakdown of the sudden approximation.

Analysis links empirical occupancies to shell-model predictions.

Abstract

The body of experimental measurements of intermediate-energy reactions that remove a single nucleon from a secondary beam of neutron- or proton-rich nuclei continues to grow. These data have been analysed consistently using an approximate, eikonal-model treatment of the reaction dynamics combined with appropriate shell-model descriptions of the projectile initial state, the bound final states spectrum of the reaction residue and single-particle removal strengths computed from their wave-function overlaps. The systematics of the ratio $R_s$ of the measured inclusive cross-section to all bound final states and the calculated cross-section to bound shell-model states -- in different regions of the nuclear chart and involving both very weakly-bound and strongly-bound valence nucleons -- is important in relating the empirically deduced orbital occupancies to those from the best available shell-model predictions. Importantly, several new higher-energy measurements, for which the sudden-approximation aspect of the dynamical description is placed on an even stronger footing, now supplement the previously-analysed measurements. These additional data sets are discussed. Their $R_s$ values are shown to conform to and reinforce the earlier-observed systematics, with no indication that the approximately linear reduction in $R_s$ with increasing nucleon separation energy is a consequence of a breakdown of the sudden approximation.