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 constrai ned to fit the spectral density obtained between 0 and 1000 cm(-1) Ass uming a static distribution, both fifth- and seventh-order processes a re capable of distinguishing the homogeneous and inhomogeneous charact er of the spectral density. Through temperature-dependent heterodyne o ptical Kerr effect studies, an upper limit (150 +/- 30 fs extrapolated to 100 degrees C) for the homogeneous lifetime in liquid water was es tablished. The intermediate fifth-order case was analyzed to incorpora te this dynamically evolving distribution of local environments and in dicates that, even for a system as complex as water, higher-order fiel d correlations can access information on its dynamic structure.