The multiplicities of postsaddle protons and $\alpha$ particles of the heavy systems ${}^{234}\mathrm{Cf}$, ${}^{240}\mathrm{Cf}$, ${}^{246}\mathrm{Cf}$, and ${}^{240}\mathrm{U}$ as functions of the postsaddle dissipation strength are calculated in the framework of a dynamical Langevin model coupled with a statistical decay model. It is found that with increasing isospin of the Cf system, the sensitivity of the postsaddle proton and $\alpha$-particle multiplicity to the dissipation strength decreases substantially, and it disappears for the ${}^{240}\mathrm{U}$ system. We suggest that on the experimental side, to accurately probe the postsaddle dissipation strength by measuring the prescission proton and $\alpha$-particle multiplicity, it is best to populate heavy compound systems with low isospin.

• Received 24 May 2009

DOI:https://doi.org/10.1103/PhysRevC.80.011601