A significant deviation from the Debye model of rotational diffusion in the
dynamics of orientational degrees of freedom in an equimolar mixture of
ellipsoids of revolution and spheres is found to begin precisely at a
temperature at which the average inherent structure energy of the system starts
falling with drop in temperature. We argue that this onset temperature
corresponds to the emergence of the alpha-process as a distinct mode of
orientational relaxation. Equally important, we find that the coupling between
the rotational and translational diffusion breaks down at a still lower
temperature where a sharp change occurs in the temperature dependence of the
average inherent structure energy.Comment: Submitted for publicatio
