Optical Kerr effect spectroscopy using time-delayed pairs of pump pulses with orthogonal polarizations.

We characterize in detail a recently introduced technique in which perpendicularly polarized pulses with controllable intensities and timing are used for the excitation step in optical Kerr effect spectroscopy. We examine the ratio of pump pulse intensities required to cancel the contribution of reorientational diffusion or of a Raman-active intramolecular vibration to the signal as a function of the delay time between excitation pulses. These results indicate that the signal can be described well as arising from the sum of independent third-order responses initiated by each pump pulse. This conclusion is further supported by using data obtained with a single pump pulse to model decays obtained with two pump pulses.