Surveying post-saddle nuclear dissipation with protons and a particles as probes

Using a Langevin model, we calculate post-saddle proton and a-particle multiplicities as a function of the post-saddle dissipation strength (β) for the heavy systems ~(234)Cf, ~(240)Cf, ~(246)Cf and ~(240)U. We find that, with increasing isospin of the system, the sensitivity of post-saddle light charged-particle multiplicities to β decreases considerably and, moreover, for 240U the charged-particle multiplicities are no longer sensitive to β. These results suggest that in order to determine the post-saddle friction strength more accurately by measuring the multiplicities of pre-scission protons and a particles, it is best to populate those heavy compound systems with low isospin.