The GDR and dissipation in hot nuclei

An overview is given of the status of experiments that use GDR γ-multiplicities (GDR clock) to extract nuclear dissipation as a function of nuclear temperature by timing the fission process from the compound nucleus equilibrium shape to the scission point. Results that indicate a rapid rise of dissipation with temperature are compared with the predictions of Fermi-liquid theory. The recent use of large BaF2 arrays allows for improved data quality for heavy-ion excitation functions. Further predictions about the transition from Fermi liquid to a classical hydrodynamical medium and the evidence from strongly damped collisions using the neutron clock are also discussed. (orig.)