High-Resolution Neutron Capture and Total Cross-Section Measurements, and the Astrophysical 95Mo(n,gamma) Reaction Rate at s-process Temperatures

TL;DR

This study provides high-resolution measurements of neutron capture on 95Mo, leading to a revised reaction rate that impacts stellar nucleosynthesis models of the s-process.

Contribution

The paper introduces new high-resolution neutron cross-section data and resonance parameters for 95Mo, improving the accuracy of the astrophysical reaction rate calculation.

Findings

Revised 95Mo(n,gamma) reaction rate is higher than previous estimates.

New resonance parameters improve understanding of neutron capture on 95Mo.

The updated rate affects s-process nucleosynthesis predictions.

Abstract

Abundances of Mo isotopes predicted by stellar models of the s process are, except for 95Mo, in good agreement with data from single grains of mainstream presolar SiC. Because the meteorite data seemed sound and no reasonable modification to stellar theory resulted in good agreement for 95Mo, it has been suggested that the recommended neutron capture reaction rate for this nuclide is 30% too low. Therefore, we have made a new determination of the 95Mo(n,gamma) reaction rate via high-resolution measurements of the neutron-capture and total cross sections of 95Mo at the Oak Ridge Electron Linear Accelerator. These data were analyzed with the R-matrix code SAMMY to obtain parameters for resonances up to En = 10 keV. Also, a small change to our capture apparatus allowed us to employ a new technique to vastly improve resonance spin and parity assignments. These new resonance parameters, together with our data in the unresolved range, were used to calculate the 95Mo(n,gamma) reaction rate at s-process temperatures. We compare the currently recommended rate to our new results and discuss their astrophysical impact.