FEMTOSECOND 2-DIMENSIONAL RAMAN-SPECTROSCOPY OF LIQUID WATER

Higher-order Raman spectra for water are calculated using the Brownian oscillator model for the nuclear degrees of freedom which is constrained to fit the spectral density obtained between 0 and 1000 cm(-1) Assuming a static distribution, both fifth- and seventh-order processes are capable of distinguishing the homogeneous and inhomogeneous character of the spectral density. Through temperature-dependent heterodyne optical Kerr effect studies, an upper limit (150 +/- 30 fs extrapolated to 100 degrees C) for the homogeneous lifetime in liquid water was established. The intermediate fifth-order case was analyzed to incorporate this dynamically evolving distribution of local environments and indicates that, even for a system as complex as water, higher-order field correlations can access information on its dynamic structure.