Damping of giant dipole resonances in hot rotating nuclei

The phonon damping model is extended to include the effect of angular momentum at finite temperature. The model is applied to the study of damping of the giant dipole resonance (GDR) in hot and noncollectively rotating spherical nuclei. The numerical results obtained for ⁸⁸Mo and ¹⁰⁶Sn show that the GDR width increases with both temperature T and angular momentum M. At T> 4 MeV and M⩽ 60ℏ the increase in the GDR width slows down for ¹⁰⁶Sn, whereas at M⩾ 80ℏ the GDR widths in both nuclei nearly saturate. By adopting the nuclear shear viscosity extracted from fission data at T= 0, it is shown that the maximal value of the angular momentum for ⁸⁸Mo and ¹⁰⁶Sn should be around 46ℏ and 55ℏ, respectively, so that the universal conjecture for the lower bound of the specific shear viscosity for all fluids is not violated up to T= 5 MeV.