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 C2v 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.