Ultrafast dichroism spectroscopy of anthracene in solution. I. Inertial versus diffusive rotation in benzyl alcohol

The experimental verification of the characteristics of suggested divisions of liquid dynamics which include ballistic, inertial and diffusive was reported. Anthracene having diffusive rotation was studied using a hydrodynamic model with slip boundary conditions and dimensions close to van der Waals values. The identification of inertial dynamics based on their viscosity independence was established by the experiment. A fast decaying component was observed in the subpicosecond region having a viscosity independent rate. The ballistic motions lasting for ≅200 fs accounted for approximately half of the total inertial decay amplitude were observed.