Significant role of fissility in evaporation residue cross sections as a probe of presaddle nuclear dissipation

Using a Langevin model, we explore the role of fissility in probing presaddle nuclear dissipation by calculating the excess of the evaporation residue cross section over its standard statistical-model value as a function of nuclear dissipation strength for nuclei 190Os and 210Po, which are taken as two representatives that have the same neutron-to-proton ratio (N/Z) but have a difference in fissility. We find that a large fissility not only amplifies the dissipation effects on the excess of evaporation residues, but also significantly increases the sensitivity of this excess to nuclear dissipation. The results suggest that in experiments, to obtain a more accurate information of nuclear dissipation inside the saddle point by measuring evaporation residue cross sections, it is best to populate among the various compound systems with equal N/Z those with high fissility.