Prompt Neutrons from Fission ofU233by 8.5- and 13.0-MeV Protons

A comparison of the number of neutrons emitted as a function of fragment mass is reported for 8.5- and 13.0-MeV proton-induced fission of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$. Results indicate that the excitation energies of the light fragments do not change appreciably, while those of the heavy fragments increase with increasing incident energy. The increase in fragment excitation for masses of ∼132 amu ($Z\cong 50$, $N\cong 82$) is significantly greater than that in compound-nucleus excitation and is accompanied by a decrease in fragment kinetic energy.