Negative Pion Activation of Bromine

Radiochemical studies of the reactions of ${\pi }^{-}$ mesons with bromine, silver, and the light elements present in photographic emulsions should assist considerably in the interpretation of data obtained with photographic plates. The results for bromine with 122-Mev negative pions expending their full range in the element include: Peak yield of about 7 percent for ${\mathrm{As}}^{76}$ (ejection of 1 proton and 2 or 4 neutrons depending on which Br isotope absorbs the pion); the ratio of the number of neutrons to the number of protons ejected was three to four in the most probable cases; the distribution of radioactivities appears to be reconcilable with photographic plate data if one guesses that the silver data will resemble those for bromine.