( π ± , x n ) reactions

Cross sections for the formation of the $^{76}\mathrm{Ge}{({\ensuremath{\pi}}^{+},xn)}^{76\ensuremath{-}x}\mathrm{As}$ and the $^{76}\mathrm{Se}{({\ensuremath{\pi}}^{\ensuremath{-}},xn)}^{76\ensuremath{-}x}\mathrm{As}$ reaction products were determined for values of $x$ up to six for both 100 and 180 MeV pions. The ${\ensuremath{\pi}}^{\ensuremath{-}}$ induced cross sections were consistently higher than those induced by ${\ensuremath{\pi}}^{+}$ for all nonzero values of $x$. Both the ${\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{+}$ induced cross sections appear to reach a maximum value when $x$ equals 2 or 3. The results are compared to predictions based on cascade-evaporation calculations and discussed in terms of possible mechanisms. Combining the experimental results for $x=5 \mathrm{and} 6$ with these calculations it was concluded that no significant difference exists in the excitation energy spectrum following ${\ensuremath{\pi}}^{+}$ or ${\ensuremath{\pi}}^{\ensuremath{-}}$ interaction.