SUBPICOSECOND RELAXATION OF SOLVENT PERTURBATIONS OF NONPOLAR ELECTRONIC STATES MEASURED BY TRANSIENT HOLE BURNING

The results of transient hole burning of the nonpolar solute dimethyl-s-tetrazine (DMST) in glycerol, glycerol triacetate, sorbitol hexaacetate, squalane, and hexane solutions are reported. Despite the high viscosity and diversity of chemical types of the solvents, the solvent-induced perturbations of the electronic states of DMST relax in less than 1 ps in all cases. This contrasts strongly with the relaxation of polar electronic states, which are typically slow in viscous solvents. A new type of solvent-interaction mechanism appears to be important. We suggest that short-range repulsions modulated by phonon-like solvent modes are responsible.