Adiabatic description of dissipative processes in heavy-ion reactions and fission. II. Weak versus strong coupling and the role of the collective velocity

We investigate the friction and diffusion coefficients for a collective variable (nuclear shape degree of freedom, treated classically) coupled with other (intrinsic) degrees of freedom. An adiabatic representation for the intrinsic degrees of freedom is used. The results are remarkably different from those given by linear response theory—the lowest order nonvanishing contribution to the friction coefficient is proportional to ${\dot{Q}}^3$. The physical origin of this behavior is discussed as well as the limits of validity of weak and strong coupling regimes, and their applicability to fission and deep inelastic scattering.