Significant role of angular momentum in probing nuclear dissipation

Based on a Langevin equation coupled with a statistical decay model, we explore the role of angular momentum in probing nuclear dissipation by calculating the excess of the evaporation residue cross section of the ${}^{200}\mathrm{Pb}$ nucleus over that predicted by the standard statistical model as a function of nuclear dissipation strength. Calculations show that high angular momentum not only enhances the dissipation effects on the excess of the evaporation residues substantially but also increases the sensitivity of this excess to the nuclear dissipation strength significantly. These results suggest that on the experimental side, to accurately obtain the information of nuclear dissipation inside the saddle point by measuring the evaporation residue cross section (or the fission cross section), it is best to populate those compound systems with high spins.

Figure 1

Excess of the evaporation residue cross section of ${}^{200}\mathrm{Pb}$ as a function of dissipation strength at excitation energy $E^{*}=100$ MeV and three critical angular momenta ${\ell }_c=30,50$, and $70\hslash$.

Figure 2

Excess of presaddle neutrons of ${}^{200}\mathrm{Pb}$ as a function of dissipation strength at excitation energy $E^{*}=100$ MeV and three critical angular momenta ${\ell }_c=30,50$, and $70\hslash$.

Figure 3

Same as Fig. 1 but at excitation energy $E^{*}=150$ MeV.

Figure 4

Same as Fig. 2 but at excitation energy $E^{*}=150$ MeV.