A dynamical approach to the treatment of fission fragment angular distribution is developed. The approach is based on three-dimensional Langevin dynamics for shape collective coordinates joined with the Monte Carlo algorithm for the degree of freedom associated with the projection K of the total angular momentum of the fissioning system on the symmetry axis. The relaxation time of the tilting mode τ K is estimated. From fits to experimental data on the fission fragment angular distribution of heavy fissioning compound systems, the K equilibration time is deduced to be ∼4 × 10 −21 s for temperatures ∼1-2 MeV. A modified one-body mechanism of nuclear viscosity with the reduction coefficient of the contribution from the 'wall' formula k s = 0.25 has been used in calculations.

No abstract