π−andμ−Meson-Induced Fission

Meson-induced fission has been studied in uranium-loaded Ilford C-2 emulsions exposed to the ${\pi }^{-}$ and ${\mu }^{-}$ meson beams of the University of Chicago cyclotron. 3762 ${\pi }^{-}$ endings were studied including 16 fission events. 3573 ${\mu }^{-}$ endings were studied including 7 fission events. The probability of a ${\pi }^{-}$ meson ending in fission is found to be (4.3±1.5)×${10}^{-3\mathrm{}}$ in C-2 emulsion containing 0.052 g ${\mathrm{cm}}^{-3\mathrm{}}$ of uranium. The corresponding probability for ${\mu }^{-}$ mesons is found to be (1.7±0.7)×${10}^{-3\mathrm{}}$. Assuming that the emulsion is a homogeneous mixture and that the atomic capture probability is proportional to $Z$, it is found that (37±13) percent of ${\pi }^{-}$ absorptions in uranium produce fission and (15±6) percent of ${\mu }^{-}$ absorptions produce fission. If the emulsion is considered to be composed of AgBr and gelatin with the uranium in the gelatin, the corresponding percentages are found to be (18±6) percent and (7±3) percent.