Competition between Fission and Neutron Emission in Excited Heavy Nuclei

The yields of the disintegration products of uranium and thorium bombarded with 340-Mev protons have been calculated from the intranuclear-cascade results of Metropolis et al. together with several alternative treatments of neutron evaporation. Several different assumptions concerning fission as a competing process were tested. The yields resulting from these different assumptions have been compared with the experimental results of Lindner and Osborne. The results point to the nonvariance of the quantity $\frac{{\Gamma }_n}{{\Gamma }_f}$ with change in nuclear excitation in the energy range below 100 Mev. They also indicate that the model used for calculating these high-energy reactions in heavy nuclei is poor for estimating yields of nuclei very close to the target nucleus (previously noted) and of nuclei with charge much less than that of the target nucleus. This inadequacy appears to be associated with the cascade stage of the calculation.