Isospin effects on the evaporation residue spin distribution

Based on a Langevin equation coupled with a statistical decay model, we have studied the evaporation residue spin distribution of the nuclei ¹⁹⁴Pb, ²⁰⁰Pb, ²⁰⁰Pb, and ²⁰⁰Os, and extracted a presaddle nuclear dissipation strength of 5×10²¹s^-1 by comparing our results with the measured spin distribution of ²⁰⁰Pb produced in the ¹⁶O+¹⁸⁴W reaction. We find that with increasing isospin of the system, the sensitivity of the spin distribution to nuclear dissipation decreases substantially. Moreover, for ²⁰⁰Os, this spin distribution is no longer sensitive to the nuclear dissipation. These results suggest that on the experimental side, to accurately obtain the information of presaddle dissipation strength by measuring the evaporation residue spin distribution, it is best to populate those systems with low isospin.