E. G. Ryabov

Consistent application of the finite-range liquid-drop model to Langevin fission dynamics of hot rotating nuclei

A generalized finite-range liquid-drop model based on the Yukawa-plusexponential potential was applied to describe fission dynamics of hot rotating nuclei. The potential energy, level-density parameter and Helmholtz free energy are calculated in a consistent way by using the generalized finiterange liquid-drop model. The level-density parameter was approximated by a leptodermous-type expression. The coefficients of this expansion are in surprisingly good agreement with those obtained earlier by Ignatyuk and co-workers. The results of Langevin dynamical calculations of the mean prescission neutron multiplicity and fission probability are practically the same both for the level-density parameter calculated with Ignatyuk’s coefficients and the one calculated using the generalized finite-range liquid-drop model. This fact lets us assume that all previous results of dynamical Langevin calculations performed with Ignatyuk’s level-density parameter stay reliable.

Investigation of dissipation in the tilting degree of freedom from four-dimensional Langevin dynamics of heavy-ion-induced fission

A four-dimensional dynamical model based on Langevin equations was applied to calculate a wide set of experimental observables for heavy fissioning compound nuclei. Three collective shape coordinates plus the tilting coordinate were considered dynamically from the ground state deformation to the scission into fission fragments. A modified one-body mechanism for nuclear dissipation with a reduction coefficient ks of the contribution from a ‘wall’ formula was used for shapes parameters. Different possibilities of deformation-dependent dissipation coefficient for the tilting coordinate () were investigated. Presented results demonstrate that the influence of the ks and γK parameters on the calculated quantities can be selectively probed. The nuclear viscosity with respect to the nuclear shape parameters influences the , the fission fragment mass–energy distribution parameters, and the angular distribution of fission fragments. At the same time the viscosity coefficient γK affects the angular distribution of fission fragments only. The independence of anisotropy on the fission fragment mass is found at both Langevin calculations performed with deformation-dependent and constant γK coefficients.

Analysis of angular momentum dependence of fission fragment mass-energy distribution within Langevin dynamics

Dependence of fission fragment mass-energy distribution on the angular momentum is studied within Langevin dynamics. The calculations are performed in the framework of the generalized temperature-dependent finite-range liquid drop model. The analysis is done for five compound nuclear systems representing heavy fissioning nuclei, medium fissioning nuclei, and a light fissioning one with the angular momentum varied in a wide range from l = 0 to 70ħ. The coefficients d〈EK〉/dl2 and \(d\sigma _{{\rm E}_{\rm K} }^2 /dl^2 \) are extracted. Previous analysis of the dσM2/dl2 coefficient is generalized. Excitation energy dependence of the fission fragment mass-energy distribution is also found. The qualitative comparison of the extracted values with the experimental data reveals good agreement for all the cases. The calculated values of the coefficients dσM2/dl2 and \(d\sigma _{{\rm E}_{\rm K} }^2 /dl^2 \) are functions of the angular momentum, in contrast to the experimental estimations.