<title>Four-photon polarization spectroscopy of liquid</title>

Abstract

The data on water and water solutions four-photon spectroscopy are presented. In the low frequency spectral band (0 - 100 cm^-1) the four-photon spectra of intermolecular and collective vibrations of water molecules are predicted theoretically and observed experimentally. Anisotropy relaxation processes in associated liquids can be studied effectively with the use of four-photon polarization spectroscopy. In contrast to spontaneous Rayleigh wing scattering, the four-photon signal contains an interference of Kerr, Rayleigh, and Brillouin nonlinearities, which deforms specifically the detected spectrum. This fact allows mutual calibration of cubic nonlinearities related to above mentioned processes.