The energy dependence of the $\mathrm{np}$ charge exchange cross section, the angular dependence of the free ${\pi }^{\pm }p$ cross section ratio, and nucleon "absorption" due to quasielastic scattering are significant in predicting (${\pi }^{\pm }$,${\pi }^{\pm }N$) ratios. When these effects are taken into account, recent ($\pi$,$\pi N$) coincidence data can be understood in the impulse approximation picture, with the recoil nucleon subject to charge exchange on leaving the nucleus.

NUCLEAR REACTIONS Ratios of $\sigma (\pi , \pi N)$ when final $\pi$ and/or $N$ observed: ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at $T_{\pi }=180, 190, 255$ MeV. Differences from radiochemical experiments.

• Received 13 November 1979

DOI:https://doi.org/10.1103/PhysRevC.21.1974