Complete Determination of Intermolecular Spectral Densities of Liquids Using Position-Sensitive Kerr Lens Spectroscopy

Femtosecond position-sensitive Kerr lens spectroscopy is demonstrated to facilitate the direct and complete measurement of the third-order material response function, R (3) ( t ). The real parts of tensor element response, ( t ) and ( t ), for liquid CS 2 have been measured and are quantitatively compared to the optical Kerr effect response, ( t ) + ( t ). The intermolecular Raman spectral densities are also obtained for each tensor element through Fourier transform. The relationship among these spectral densities is discussed with regard to the nature of the underlying intermolecular motions in liquid CS 2 . Specifically, we find that the intermolecular depolarization ratio is frequency independent with a value of 0.7 ± 0.1 in the 0−150 cm -1 region.