High precision $^{113}$In($\alpha,\alpha$)$^{113}$In elastic scattering at energies around the Coulomb barrier for the astrophysical $\gamma$ process

Abstract

The $\gamma$ process in supernova explosions is thought to explain the origin of proton-rich isotopes between Se and Hg, the so-called $p$ nuclei. The majority of the reaction rates for $\gamma$ process reaction network studies has to be predicted in Hauser-Feshbach statistical model calculations using global optical potential parameterizations. While the nucleon+nucleus optical potential is fairly known, for the $\alpha$+nucleus optical potential several different parameterizations exist and large deviations are found between the predictions calculated using different parameter sets. By the measurement of elastic $\alpha$-scattering angular distributions at energies around the Coulomb barrier a comprehensive test for the different global $\alpha$+nucleus optical potential parameter sets is provided. Between 20$^{\circ}$ and 175$^{\circ}$ complete elastic alpha scattering angular distributions were measured on the $^{113}$In \textit{p} nucleus with high precision at E$_{c.m.}$ = 15.59 and 18.82 MeV. The elastic scattering cross sections of the $^{113}$In($\alpha$,$\alpha$)$^{113}$In reaction were measured for the first time at energies close to the astrophysically relevant energy region. The high precision experimental data were used to evaluate the predictions of the recent global and regional $\alpha$+nucleus optical potentials. Parameters for a local $\alpha$+nucleus optical potential were derived from the measured angular distributions. Predictions for the reaction cross sections of $^{113}$In($\alpha,\gamma$)$^{117}$Sb and $^{113}$In($\alpha$,n)$^{116}$Sb at astrophysically relevant energies were given using the global and local optical potential parameterizations.