Assessing the impact of valence sd neutrons and protons on fusion

TL;DR

This study investigates how valence sd neutrons and protons influence fusion cross-sections above the barrier, revealing trends not captured by existing models, through experimental comparisons and theoretical analysis.

Contribution

It provides new experimental data on fusion involving sd-shell nuclei and evaluates the performance of current theoretical models against these data.

Findings

Experimental fusion cross-sections show trends not predicted by models.

Both analytical and Hartree-Fock models fail to reproduce observed trends.

Valence sd nucleons significantly affect fusion dynamics above the barrier.

Abstract

Experimental above-barrier fusion cross-sections for $^{17}$F + $^{12}$C are compared to the fusion excitation functions for $^{16,18}$O, $^{19}$F, and $^{20}$Ne ions on a carbon target. In comparing the different systems both the differing static size of the incident ions and changes in fusion barrier are accounted for by examining the reduced fusion cross-section. Remaining trends of the fusion cross-section above the barrier which reflect the sensitive interplay of the sd protons and neutrons are observed. The experimental data are also compared to both a widely-used analytical model of near-barrier fusion, as well as a time-dependent Hartree-Fock model. Both models fail to describe the trends observed.