Prompt gamma rays from nuclear reactions induced by 380-MeVπ

Using a Ge(Li) detector, $\gamma$-ray spectra coincident with incident 380-MeV ${\pi }^{-}$ have been measured for targets of S, Ar, Ca, V, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, and As. The production cross sections for identified $\gamma$ rays vary from about 200 to about 500 mb, depending on the target, although there is considerable uncertainty in the absolute cross sections. Comparison with data taken at lower energies leads to the conclusion that the spectra do not significantly change with pion energy over the range $100 \mathrm{MeV}\le T_{\pi }\le 400 \mathrm{MeV}$. Formation of nuclei which can be made by removing an integral number of $\alpha$ particles, or, in the case of odd targets, a triton plus an integral number of $\alpha$ particles, appears to be usually favored but it is not certain that it is necessary to invoke special clustering effects in order to explain the presently available data. Some clues as to the reaction mechanism can be found in the data.