Elastic scattering of 65 MeV positive and negative pions from nickel isotopes

Angular distributions of elastic differential cross sections were obtained at 65 MeV using positive and negative pions scattered from ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$. The data were compared to predictions using the Michigan State University optical potential. These predictions are not in good agreement with the data. The negative pion cross sections are more poorly described than the positive pion cross sections. The p-wave part of the potential is observed to be especially sensitive to this Coulomb-nuclear interference effect.