FREQUENCY-RESOLVED INTERFEROMETRIC COHERENT RAMAN-SPECTROSCOPY WITH INCOHERENT-LIGHT - RAMAN FREQUENCY-SHIFTS, DEPHASING RATE CONSTANTS, AND NONRESONANT HYPERPOLARIZABILITIES OF MIXTURES OF BENZENE IN HEXANE

A newly developed frequency and time resolved coherent anti-Stokes Ram an scattering (CARS) technique is used to study properties of the A(1g ) ring breathing mode of benzene in a dilution series of liquid mixtur es with n-hexane. Recent advances in the interferometric use of incohe rent light in CARS measurements (I-(2)CARS) provide excellent precisio n in the recovered dephasing rate constants, vibrational frequencies, and the ratios of the resonant to non-resonant contributions to the si gnal. Using this technique we observe a more than two-fold decrease in the dephasing rate constant of the vibration, accompanied by a 0.54 c m(-1) increase in the vibrational frequency in the limit of infinite d ilution of benzene in n-hexane. These changes in the vibrational spect rum are discussed in terms of the condensed phase dynamics that are re sponsible. It is also seen how the non-resonant contributions to the s ignal manifest themselves quantitatively in these frequency and time r esolved I-(2)CARS measurements. (C) 1997 Elsevier Science B.V.