Fission of Heavy Nuclei at Higher Excitation Energies in a Dynamic Model

The dynamic model of asymmetric fission used in calculating the mass and kinetic energy distributions of the fragments from thermal-neutron-induced fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ is employed here to calculate these distributions for fission at higher excitation energies and for other heavy nuclei at low excitation energies. The model itself is investigated with respect to the semiphenomenological shell correction. It is found that the mass distribution of the fragments in the reaction ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}\mathrm{}(n,f)\mathrm{}$, which for thermal neutrons is strongly peaked at the heavy-fragment mass 132, goes over into a symmetric mass distribution at a compound-nuclear temperature of about 6 MeV.