SENSITIVITY OF THE EVAPORATION RESIDUE PRODUCTION TO DYNAMICAL EFFECTS IN HIGHLY FISSILE COMPOUND NUCLEI

We investigate the sensitivity of statistical model calculations of in dividual evaporation residue (ER) production on the nuclear shape evol ution and viscosity. To this aim we analyze the de-excitation of the A c-117 compound nucleus formed at the excitation energies between 36 an d 90 MeV. We find a strong dependence of the calculated results on the nuclear dissipation and shape evolution, which make evaporation resid ues a useful tool for investigating dynamical effects. We indicate a n ew method of estimating the nuclear viscosity and claim that the stati stical model interpretation of the ER's does not exclude high values f or the viscosity parameter.