A classical time-frequency theory of transient absorption spectroscopy

A method of quasiclassical dynamics simulation of transient pump-probe spectra is developed based on an exact time-frequency interference picture for the nonlinear spectroscopy in condensed phases. The present approach allows a proper treatment of the effect of light coherence and interference on material dynamics, and is applicable to fields with arbitrary time scales and profiles. Both the sequential and the coherent contributions to the spectral signal are considered. The proposed numerical approach is suitable to simulate the experimental spectra of molecular systems with many degrees of freedom. A numerical demonstration is presented for the transient laser induced fluorescence (LIF) of I-2 molecule at 320 K excited by a pair of pulses. (C) 1997 American of Physics.