Measurement of (alpha,n) reaction cross sections of erbium isotopes for testing astrophysical rate predictions

TL;DR

This study measures alpha-induced reaction cross sections on erbium isotopes to test and improve the predictive accuracy of astrophysical reaction rate models, addressing discrepancies in p-nuclei abundance predictions.

Contribution

It provides experimental data on erbium isotopes to validate and suggest modifications to the alpha+nucleus optical potential used in astrophysical models.

Findings

Measured cross sections near astrophysical energies.

Indicates a need for low-energy optical potential modifications.

Supports improved modeling of p-nuclei production.

Abstract

The $\gamma$-process in core-collapse and/or type Ia supernova explosions is thought to explain the origin of the majority of the so-called $p$ nuclei (the 35 proton-rich isotopes between Se and Hg). Reaction rates for $\gamma$-process reaction network studies have to be predicted using Hauser-Feshbach statistical model calculations. Recent investigations have shown problems in the prediction of $\alpha$-widths at astrophysical energies which are an essential input for the statistical model. It has an impact on the reliability of abundance predictions in the upper mass range of the $p$ nuclei. With the measurement of the $^{164,166}$Er($\alpha$,n)$^{167,169}$Yb reaction cross sections at energies close to the astrophysically relevant energy range we tested the recently suggested low energy modification of the $\alpha$+nucleus optical potential in a mass region where $\gamma$-process calculations exhibit an underproduction of the $p$ nuclei. Using the same optical potential for the $\alpha$-width which was derived from combined $^{162}$Er($\alpha$,n) and $^{162}$Er($\alpha$,$\gamma$) measurement makes it plausible that a low-energy modification of the optical $\alpha$+nucleus potential is needed.