Hadi Eslamizadeh

*A two-dimensional dynamical model based on Langevin equation was used to study the fission dynamics of the compound nuclei 206po and 168Yb produced in the reactions 12C 194pt and 18O 150Sm , respectively. The fission cross section and average pre-scission neutron multiplicity were calculated for the compound nuclei 206po ,168Yb and results of the calculations compared with the experimental data. The elongation coordinate was used as the first dimension and the projection of the total spin of the compound nucleus onto the symmetry axis, , considered as the second dimension in the Langevin dynamical calculations. In the two-dimensional calculations, a constant dissipation coefficient of K and a non-constant dissipation coefficient have been used to reproduce the above-mentioned experimental data. It was shown that two-dimensional Langevin equation can satisfactorily reproduce the fission cross section and average pre-scission neutron multiplicity for the compound nuclei 206Po and 168Yb by using constant values of the dissipation coefficient of K equal to 0.18 and 0.2 for the compound nuclei 206Po and 168Yb ,respectively.