NONLINEAR RESPONSE FUNCTIONS FOR BIREFRINGENCE AND DICHROISM MEASUREMENTS IN CONDENSED PHASES

The fourth-rank tensorial nonlinear response function which controls the response of a chromophore in the condensed phase to three arbitrarily polarized external fields is calculated. Internal (vibrational and rotational) degrees of freedom are incorporated using wave packets in Liouville space (the doorway/window picture). The rotational contribution of the chromophore is expressed in terms of a conditional probability for the rotational diffusion model. We apply this formalism to transient dichroism and birefringence spectroscopies.