SPIN DISTRIBUTION OF DOUBLE NUCLEAR FISSION WITH ACCOUNT FOR BENDING- AND WRIGGLING- MODES

A theoretical description of the nature of the spin distribution (CP) of fragments of low-energy induced and spontaneous double fission of nuclei is carried out. For two deformed fission prefragments, a mechanism for pumping large values of their relative orbital momenta L and spins J, due to the combined influence of bending and wriggling vibrations, has been established, and analytical formulas for describing CP within the framework of such a mechanism have been obtained for the first time. It is emphasized that for this mechanism, the nucleus remains “cold” in the fission process, while in the statistical model it heats up to temperatures 1 MeV. A comparison of the calculated CP for forced double fission of actinide nuclei and with the available experimental data showed reasonable agreement both in terms of the magnitude of the average spin values and in the sawtooth shape of the dependence of CP on the atomic number of fragments, which confirms the reliability of the pumping mechanism of large spin values of deformed fission fragments. For spontaneous double fission of the nucleus , possible reasons for the discrepancy between the theoretical CP and the experiment are indicated.