Muon- and Pion-Induced Fission of Uranium Isotopes

We have measured the energy distributions of fission fragments following formation of muonic and pionic ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$. We have confirmed earlier results on the mean lives for muon capture by ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ and extended the study to ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$. Additional data have also been obtained on the process whereby a muon induces fission by transferring its excitation energy to the nucleus in a radiationless transition to the $1s$ level.