ULTRAFAST SOLVENT DYNAMICS - CONNECTION BETWEEN TIME RESOLVED FLUORESCENCE AND OPTICAL KERR MEASUREMENTS

The vibrational characteristics of liquid dynamics are used to describ e the ultrafast relaxations observed in time-dependent fluorescence St okes shift [J. Chem. Phys. 95, 4715 (1991)] and heterodyne detected op tical Kerr effect measurements on acetonitrile, via a Brownian oscilla tor model. Introducing a frequency distribution of vibrational modes m akes it possible to compare the two experiments. The ultrafast decays observed in the fluorescence Stokes shift and optical Kerr signals are produced by destructive superposition of the high frequency, underdam ped modes.