Alpha-induced reaction cross section measurements on 151Eu for the astrophysical gamma-process

TL;DR

This study measures the cross sections of specific europium reactions relevant to the astrophysical gamma-process, revealing discrepancies with models and suggesting adjustments to reaction rates for better astrophysical modeling.

Contribution

It provides new experimental cross section data for 151Eu reactions at low energies and compares these with statistical model predictions, highlighting the need for improved theoretical descriptions.

Findings

Statistical models overestimate cross sections by about a factor of two.

Discrepancies are due to inadequate alpha+nucleus channel descriptions.

A reduction of the reaction rate for 151Eu(alpha,gamma)155Tb is recommended.

Abstract

In order to extend the experimental database relevant for the astrophysical gamma-process towards the unexplored heavier mass region, the cross sections of the 151Eu(alpha,gamma)155Tb and 151Eu(alpha,n)154Tb reactions have been measured at low energies between 12 and 17 MeV using the activation technique. The results are compared with the predictions of statistical model calculations and it is found that the calculations overestimate the cross sections by about a factor of two. A sensitivity analysis shows that this discrepancy is caused by the inadequate description of the alpha+nucleus channel. A factor of two reduction of the reaction rate of 151Eu(alpha,gamma)155Tb in gamma-process network calculations with respect to theoretical rates using the optical potential by McFadden and Satchler (1966) is recommended.