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 ${}^{144}\mathrm{Sm}$, an intriguing $p$ nucleus that is semimagic with 82 neutrons. This work presents new experimental data on $\alpha$ elastic and inelastic scattering on ${}^{148}\mathrm{Sm}$, 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.

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• Elastic scattering reactions
• Models & methods for nuclear reactions
• Nuclear astrophysics
• Nuclear reactions
• Nucleosynthesis in explosive environments
• 90 ≤ A ≤ 149
• Optical, coupled-channel & distorted wave models