Investigation of alpha-induced reactions on 130Ba and 132Ba and their importance for the synthesis of heavy p nuclei

TL;DR

This study measures alpha-induced reaction cross sections on barium isotopes 130Ba and 132Ba to improve astrophysical models of heavy p nucleus synthesis, providing new reaction rates and comparing them with statistical model predictions.

Contribution

It provides new experimental cross section data for alpha reactions on 130Ba and 132Ba relevant to the gamma process in nucleosynthesis, and compares these with statistical model calculations.

Findings

Alpha reaction cross sections measured between 11.6 and 16 MeV.

Standard alpha+nucleus optical potential reproduces (alpha,n) data.

New stellar reaction rates for 130Ba and 132Ba reactions are presented.

Abstract

Captures of alpha particles on the proton-richest Barium isotope, 130Ba, have been studied in order to provide cross section data for the modeling of the astrophysical gamma process. The cross sections of the 130Ba(alpha,gamma)134Ce and 130Ba(alpha,n)133Ce reactions have been measured with the activation technique in the center-of mass energy range between 11.6 and 16 MeV, close above the astrophysically relevant energies. As a side result, the cross section of the 132Ba(alpha,n)135Ce reaction has also been measured. The results are compared with the prediction of statistical model calculations, using different input parameters such as alpha+nucleus optical potentials. It is found that the (alpha,n) data can be reproduced employing the standard alpha+nucleus optical potential widely used in astrophysical applications. Assuming its validity also in the astrophysically relevant energy window, we present new stellar reaction rates for 130Ba(alpha,gamma)134Ce and 132Ba(alpha,gamma)136Ce and their inverse reactions calculated with the SMARAGD statistical model code. The highly increased 136Ce(gamma,alpha)132Ba rate implies that the p nucleus 130Ba cannot directly receive contributions from the Ce isotopic chain. Further measurements are required to better constrain this result.