(π,πN) reactions onMg25andAu197

Activation cross sections have been measured for the reactions ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$(${\pi }^{\pm }$,${\pi }^{\pm }N$)${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$(${\pi }^{\pm }$,${\pi }^{\pm }N$)${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ between 100 and 300 MeV. The cross section ratios $R_p=\frac{\sigma \left({\pi }^{+}\right)}{\sigma \left({\pi }^{-}\right)}$ and $R_p=\frac{\sigma \left({\pi }^{-}\right)}{\sigma \left({\pi }^{+}\right)}$ are smaller than the corresponding free-particle ratios in all cases. Comparisons with the predictions of intranuclear cascade calculations and the nucleon charge-exchange model indicate that the former gives good agreement for a heavy nucleus but not for light nuclei, while the inverse is true for the latter model.