Elastic scattering of 30 MeV positive and negative pions from nickel isotopes

Elastic cross sections for the scattering of positive and negative pions from ${}_{}{}^{58}{}_{}{}^{}$,60,64Ni were measured at 30 MeV incident pion energy. A clear isotope effect was observed in the ${\pi }^{\mathrm{-}}$ cross sections while no effect was observed in the ${\pi }^{+}$ cross sections. The cross sections were compared to predictions made by various optical model calculations. In general, both ${\pi }^{+}$ and ${\pi }^{\mathrm{-}}$ cross sections were poorly described and the ${\pi }^{\mathrm{-}}$ isotope effects were not well reproduced. Anomalous effects first observed in pionic atoms may also appear in the present data.