Dynamical structure of water by Raman spectroscopy

Raman spectra of liquid water have a broad background extended to 4000 cm(-1) as well as molecular vibrational modes. Depolarized Raman spectra below 250 cm(-1) in liquid water are well interpreted with a superposition of two damped harmonic oscillators and one Cole-Cole type relaxation mode. Two damped harmonic oscillators are interpreted as stretching and bending vibration modes of a temporal tetrahedral-like structure of five water molecules. High-frequency Raman spectra between 1600 cm(-1) and 4000 cm(-1) in liquid water are well explained by molecular vibration modes of a temporal C-2v tetrahedral-like structure around oxygen atom. This interpretation of high frequency spectra is consistent with the interpretation of low-frequency vibrational modes below 250 cm(-1). Moreover, the high frequency tail of the above Cole-Cole type relaxation mode could explain the broad background spectra in liquid water. (C) 1998 Elsevier Science B.V.