Four-photon laser spectroscopy of low-frequency rotational resonances of H2O molecules in the liquid phase

A clearly pronounced structure of the Rayleigh wing consisting of a great number of components is measured in the range 0–100 cm −1 using four-photon polarization spectroscopy. The features observed are compared with the calculated IR spectra of H 2 O molecules in the gas phase taken from the HITRAN database. A good correlation between the frequency positions of the observed and calculated lines points to the possibility of hindered rotation of water molecules in liquid.