Can the independent binary collision theory describe the nonlinear solvent density dependence of the vibrational energy relaxation rate?

Serious doubt has been cast on the validity of the independent binary collision (IBC) theory for describing nonlinear solvent density effects on the rate of vibrational to translational and rotational energy transfer [P. S. Dardi and R. I. Cukier, J. Chem. Phys. 89, 4145 (1988)]. Here, we compare the IBC theory predictions with experiment. Inconsistencies in previous applications of the IBC theory are discussed. Correcting these inconsistencies, we find that the agreement between the IBC theory and experiment is not good. Furthermore, we find that the collision diameter needed to obtain the best fit with experiment is significantly temperature dependent. We conclude that the IBC theory is not a valid theory to describe solvent density effects on vibrational relaxation.