Fissility effects on evaporation residue spin distributions

Based on a dynamical Langevin equation coupled with a statistical decay model, we calculate the spin distribution of evaporation residue cross sections of nuclei ¹⁹⁰Os and ²¹⁰Po which have the same neutron-to-proton ratio N/Z$N/Z$ but have a difference in fissility. We find that a large fissility enhances the sensitivity of the residue spin distribution to pre-saddle friction substantially. The results suggest that on the experimental side, to obtain accurate information of pre-saddle dissipation strength by measuring the evaporation residue spin distribution it is optimal to populate among various compound systems with equal N/Z$N/Z$ those with high fissility.