Effects of N/Z on Spin Distribution of Evaporation Residue Cross Section as a Probe of Nuclear Dissipation

The spin distribution of the evaporation residue cross section of nuclei ¹⁹⁴Pb, ²⁰⁰Pb, ²⁰⁶Pb, and ²⁰⁰Os are calculated via a Langevin equation coupled with a statistical decay model. It is shown that with increasing the neutron-to-proton ratio (N/Z) of the system, the sensitivity of the spin distribution to the nuclear dissipation is decreased significantly. Moreover, for ²⁰⁰Os this spin distribution is no longer sensitive to the nuclear dissipation. These results suggest that to obtain a more accurate pre-saddle viscosity coefficient through the measurement of the evaporation residue spin distribution, it is best to yield those compound systems with low N/Z.