  We demonstrate effective equilibration for unitary quantum dynamics under
conditions of classical chaos. Focusing on the paradigmatic example of the
Dicke model, we show how a constructive description of the thermalization
process is facilitated by the Glauber $Q$ or Husimi function, for which the
evolution equation turns out to be of Fokker-Planck type. The equation
describes a competition of classical drift and quantum diffusion in contractive
and expansive directions. By this mechanism the system follows a 'quantum
smoothened' approach to equilibrium, which avoids the notorious singularities
inherent to classical chaotic flows.
