Photofission ofTh232with 9, 15, and 38 MeV peak bremsstrahlung

The mass-yield distribution of fission products following photofission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ using peak bremsstrahlung energies of 9, 15, and 38 MeV were measured by $\gamma$ spectrometry for 25 mass chains in the light and heavy mass wings. Fission yields for mass chains 85, 87, 88, 138, and 146 were measured for the first time for the photofission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ in this work. Several fractional chain yields were measured and various postulates of charge distribution were tested to correlate the experimental data. The Nethaway modified empirical Coryell method showed the best correlation with the observed charge distributions. Evidence for fine structure was observed from the 9 and 15 MeV irradiations in both the heavy and light mass wings with peaks occurring at $A=134\mathrm{} \mathrm{and} 93$, respectively. The inner portions of the mass wings both exhibited increasing splay as the irradiation energy was increased, indicating that symmetric fission was enhanced with increased energy.