Studies of $\rm ^{144,148}Sm+\alpha$ potential for the $p$-process nucleosynthesis
Nucleosynthesis reaction networks leading to $p$-nuclei involve a combination of different types of photodisintegration and capture reactions, as well as $\beta^+$ decays or electron captures. Photodisintegration reactions involving $\alpha$ particles present a particular interest as they serve as branching points of the reaction networks. The cross sections of these reactions depend crucially on the $\alpha$-nucleus interaction. The $\alpha$ optical model potential (AOMP) is determined mostly by means of experimental differential elastic scattering distributions. Several previous studies have focused on the case of $\rm ^{144}Sm$, an intriguing $p$-nucleus that is semi-magic with 82 neutrons. This work presents new experimental data on $\alpha$ elastic and inelastic scattering on $\rm ^{148}Sm$, its closest stable isotope. Isotopic effects on the description of the AOMP are studied, as well as their consequences on the prediction of $\alpha$-induced reaction cross sections at astrophysical energies. It is shown that the isotopic ratio for $(\alpha,\gamma)$ cross sections can be multiplied up to a factor of two when these effects are included.