Fluctuation-dissipative dynamics of formation of fission fragment mass distribution

The dispersions of the mass distribution of fission fragments from excited compound nuclei (the temperature of the nuclei in the saddle point Tsd ≅ 1.5 MeV) are calculated in a wide range of the parameter Z2/A (from 30 to 44). The calculations are carried out in the model based on the Fokker-Planck equation (FPE) for the distribution function of three most important collective coordinates which describe deformations of the fissionable nucleus: elongation, mass asymmetry, neck parameter, and conjugate momenta. The model takes into account the real coordinate dependence of all FPE coefficients calculated in the hydrodynamical approximation. The angular momentum effect on the mass distribution dispersion values is studied. The calculations reproduce the observed strong growth of the dispersions of the mass distribution of fission fragments of the compound nuclei at Z2/A > 35