The hybrid model has been modified for application in the energy region involved in capture of stopped negative pions (140 MeV). Comparisons of the improved formulation have been made with data from reactions induced by protons up to 164 MeV and the agreement was good. The model was used to predict n and p spectra and activation yields from stopped ${\pi }^{-}$ capture on targets from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ to ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$, assuming a predominant quasideuteron capture mechanism. Predictions are given for primary versus secondary emission contributions to the spectra. Qualitative predictions for nn, np, and pp angular correlations are presented. Sensitivity of spectra and yields to parameters related to the nuclear density at which capture occurs is illustrated. While overall comparisons between calculated and experimental results are quite satisfactory, more detailed analyses suggest that a geometry dependent formulation integrating along the density profile for ${\pi }^{-}$ capture will be necessary, coupled with explicit treatment of enhanced nucleon emission probability versus nucleon induced reactions (due to momentum differences in the entrance channels) if such model results are to simultaneously reproduce particle spectra and yields.

NUCLEAR REACTIONS Reactions induced by stopped ${\pi }^{-}$; calculate proton and neutron emission spectra and yields ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ to ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ targets using hybrid plus Weisskopf models.

• Received 23 March 1983

DOI:https://doi.org/10.1103/PhysRevC.28.1648