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 Raman scattering (CARS) technique is used to study properties of the A(1g) ring breathing mode of benzene in a dilution series of liquid mixtures with n-hexane. Recent advances in the interferometric use of incoherent light in CARS measurements (I-(2)CARS) provide excellent precision in the recovered dephasing rate constants, vibrational frequencies, and the ratios of the resonant to non-resonant contributions to the signal. Using this technique we observe a more than two-fold decrease in the dephasing rate constant of the vibration, accompanied by a 0.54 cm(-1) increase in the vibrational frequency in the limit of infinite dilution of benzene in n-hexane. These changes in the vibrational spectrum are discussed in terms of the condensed phase dynamics that are responsible. It is also seen how the non-resonant contributions to the signal manifest themselves quantitatively in these frequency and time resolved I-(2)CARS measurements. (C) 1997 Elsevier Science B.V.