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Differential cross sections for the (..pi../sup -/,n) reactions in /sup 3/He and /sup 4/He have been measured at energies of 100, 200, and 290 MeV. The angular distributions for /sup 3/He and /sup 4/He are different, with the /sup 4/He characterized by an oscillatory pattern with a dip at a fixed angle of approx. = 70/sup 0/. The forward-angle cross sections show a simple dependence upon momentum transfer for both /sup 3/He and /sup 4/He. These results are discussed in the context of single-nucleon and multinucleon reaction diagrams.

Differential cross sections for the reaction /sup 3/He(..pi../sup -/,..pi../sup 0/)/sup 3/H at energies of 200, 250, 275, and 290 MeV over the angular region 80 /sup 0/ < or approx. = theta/sub c.m./ < or approx. = 150/sup 0/ are presented. Comparison is made with theoretical predictions based on Glauber theory and optical-potential calculations. Neither approach gives a satisfactory description on the data; in particular, the observed energy dependence is much smaller than the theoretical predictions.

Outgoing-nucleon charge exchange has been used to explain reduction in ..pi..-N isospin selectivity in a large number of nucleon-removal experiments. The present work tests the validity of this model by measuring the total cross sections for nucleon removal to the 4.44-MeV, T = 0 and the 15.11-MeV, T = 1 states in /sup 12/C, where analog charge exchange is possible for the latter, but not the former state.

Total cross sections for the knockout reactions $^{7}\mathrm{Li}({\ensuremath{\pi}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}}n)^{6}\mathrm{Li}$ and $^{7}\mathrm{Li}({\ensuremath{\pi}}^{+},{\ensuremath{\pi}}^{+}n)^{6}\mathrm{Li}$ to 3.56-MeV ${0}^{+}$ $T=1$ state have been measured at ten energies between 50 and 290 MeV by detecting the direct $\ensuremath{\gamma}$ de-excitation. As found in previous work, the ratio $\frac{\ensuremath{\sigma}({\ensuremath{\pi}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}}n)}{\ensuremath{\sigma}({\ensuremath{\pi}}^{+},{\ensuremath{\pi}}^{+}n)}$ on the (3,3) resonance is significantly less than the value of 3 expected from free pion-nucleon results.