Uncertainties in radiative neutron-capture rates relevant to the $A\sim 80$ $r$-process peak

TL;DR

This paper investigates uncertainties in neutron-capture rates relevant to the $A\, extasciitilde 80$ r-process peak, highlighting large potential deviations and the impact of low-energy gamma enhancements on astrophysical models.

Contribution

It provides a detailed analysis of uncertainties in radiative neutron-capture cross sections for isotopes around the $A\, extasciitilde 80$ r-process peak, including effects of low-energy gamma enhancements.

Findings

Uncertainties in neutron-capture rates can be extremely large.

Low-energy gamma enhancements may significantly increase reaction rates.

Standard libraries may underestimate or misrepresent these rates.

Abstract

The rapid neutron-capture process ($r$-process) has for the first time been confirmed to take place in a neutron-star merger event. A detailed understanding of the rapid neutron-capture process is one of the holy grails in nuclear astrophysics. In this work we investigate one aspect of the $r$-process modelling: uncertainties in radiative neutron-capture cross sections and astrophysical reaction rates for isotopes of the elements Fe, Co, Ni, Cu, Zn, Ga, Ge, As, and Se. In particular, we study deviations from standard libraries used for astrophysics, and the influence of a very-low $\gamma$-energy enhancement in the average, reduced $\gamma$-decay probability on the ($n,\gamma$) rates. We find that the intrinsic uncertainties are in some cases extremely large, and that the low-energy enhancement, if present in neutron-rich nuclei, may increase the neutron-capture reaction rate significantly.