Ultrafast Vibronic Dynamics of Dye Molecules Studied by the Induced Grating Method

Abstract

In recent years numerous papers have investigated the induced grating method for the study of the ultrafast dynamics of dye molecules /1/. A quantitative understanding of the signal transients observed at short times, where the so-called coherence peak occurs, and of the polarization dependence of this effect has been lacking. In this article we present new theoretical and experimental data on the picosecond time scale for the elastic (Rayleigh) light scattering of delayed probing pulses from induced population gratings. The scattering mechanism for the so-called coherence peak is interpreted as a resonant two-step, one-photon process, which depends on the vibronic relaxation of the terminating levels in the excited electronic state. The contributions of other nonlinear processes, i.e. single-step multiphoton interactions are found to be negligible.