Multidimensional dynamical-statistical model for describing the fission of excited nuclei

A multidimensional stochastic model for describing the decay of excited nuclei is presented. The model takes into account the dynamics of thermal fluctuations of collective variables, the dissipation of the kinetic energy of collective motion, and the emission of light particles from excited nuclei. The potential energy of a deformed nucleus is calculated within the liquid-drop model with a sharp surface and within the finite-range-interaction model. The friction parameters are calculated on the basis of the one-body-dissipation model. The inertia parameters are found in the Werner-Wheeler approximation. The drift components of forces are determined in terms of the entropy of an excited nucleus. The latter in turn is computed within the Fermi gas approximation with allowance for the deformation dependence of the density-level parameter. The fission probability, the mean multiplicity of neutrons emitted prior to scission (prescission neutrons), and the variances of the mass distributions of fission fragments at the most probable kinetic-energy value are calculated on the basis of the model developed here and are compared with experimental data. The dependences of these quantities on the model parameters are considered in detail