Non-perturbative wave-packet calculations of time-resolved four-wave-mixing signals

Abstract.

We extend a method proposed by Seidner et al. [J. Chem. Phys. 103, 3998 (1995)] to extract directional terms from a time-dependent molecular polarization to obtain time-resolved four-wave-mixing (FWM) signals. Instead of employing perturbation theory, the total polarization induced in the molecular sample by the interaction with several femtosecond laser pulses is determined by solving the time-dependent Schrödinger equation for the nuclear dynamics in coupled electronic states numerically exact. Repeating the calculation for several combinations of relative phases of the involved fields leads to a linear system of equations for the contributions emitted in different directions. Gas-phase I₂ molecules serve as a numerical example.