Direct capture in the $^{130}$Sn(n,$\gamma$)$^{131}$Sn and $^{132}$Sn(n,$\gamma$)$^{133}$Sn reactions under $r$-process conditions

TL;DR

This study calculates direct capture cross sections for specific tin isotopes relevant to the r-process, using local experimental data to reduce uncertainties and estimate stellar reaction rates.

Contribution

It introduces a local adjustment method for direct capture calculations, avoiding global parameter uncertainties, and provides updated reaction rates for astrophysical models.

Findings

Calculated cross sections with less than a factor of two uncertainty

Reaction rates slightly increase with temperature

Estimated influence of low-lying resonances on rates

Abstract

The cross sections of the $^{130}$Sn(n,$\gamma$)$^{131}$Sn and $^{132}$Sn(n,$\gamma$)$^{133}$Sn reactions are calculated in the direct capture model at low energies below 1.5\,MeV. Using recent data from (d,p) transfer experiments on $^{130}$Sn and $^{132}$Sn, it is possible to avoid global input parameters with their inherent uncertainties and to determine all input to the direct capture model by local adjustments. The calculated direct capture cross sections of $^{130}$Sn and $^{132}$Sn are almost identical and have uncertainties of less than a factor of two. The stellar reaction rates $N_A < \sigma v >$ show a slight increase with temperature. Finally an estimate for the influence of low-lying resonances to the stellar reaction rates is given.