2-DIMENSIONAL FEMTOSECOND VIBRATIONAL SPECTROSCOPY OF LIQUIDS

The nonlinear optical response of liquids subjected to a series of N f emtosecond laser pulses is calculated using a multimode harmonic model for nuclear motions, with nonlinear coupling to the radiation field t hrough the coordinate dependence of the electronic polarizability. Usi ng electronically off-resonant optical fields, this multidimensional s pectroscopy is shown to provide direct information regarding the homog eneous or the inhomogeneous nature of the spectral density obtained fr om optical birefringence measurements. Complementary information can b e obtained using infrared pulses where the multiple time correlation f unctions of the nuclear dipole moment (rather than the electronic pola rizability) are being probed.