PHOTON-ECHOES IN A NONPOLAR FLUID

We calculate the photon echo signal for a nonpolar chromophore dissolved in a nonpolar solvent. Results of molecular dynamics simulations are compared to calculations in which molecular motions are taken to be ballistic, to assess the contribution of such motions to the echo decay. The validity of the conventional assumption that fluctuations in the electronic transition frequency obey Gaussian statistics is investigated for this model. We consider the role of fluctuations in the repulsive portion of the intermolecular potential in determining the echo decay. The calculations suggest that electronic dephasing in liquids may arise primarily from a slight rearrangement of the first solvation shell about the chromophore.