Relative measurements of photofission cross sections with the use of a bremsstrahlung spectrum

This survey is devoted to the investigation of fission probability by measuring photofission yields using a bremsstrahlung spectrum of the microtron with the relative measurement method in the region of energies from the threshold to the upper boundary of the fissility plateau (E < 11 MeV). The results were obtained using a unique technique for nineteen nuclei from ²³²Th to ²⁴⁹Cf. For some nuclei in the threshold energy region, detailed measurements were performed which provided the possibility of observation of new resonances in the photofission cross section. The observed resonance effects are discussed. For ²³⁴U and ^{238, 240, 242}Pu, theoretical analysis was performed to obtain the fission barrier parameters for fission channels with particular quantum states. Data of other measurements of photofission cross sections are given, along with the results obtained in the surveyed series of measurements. The data obtained using the relative measurement method is compared with data for other reactions that result in fission of the nuclei under study.