Ion-induced random electric fields in aqueous salt solutions as studied bythe four-photon polarization spectroscopy method

Using the four-photon polarization spectroscopy we have studied the Rayleig h wing spectral patterns of several aqueous salt solutions within the 0-50 cm(-1) frequency range. Within the framework of an approach allowing a repr esentation of the Rayleigh wing spectrum as two Lorentzian functions, chara cterized by the long and the short times of relaxation of an anisotropic mo de, we obtained that the short relaxation time does depend on the concentra tion of electrolyte and its type, whereas the long relaxation time does not . The effect can be qualitatively interpreted supposing that the fluctuatio ns of ionic concentration give rise to the fluctuations of local electric f ield. An instantaneous magnitude of this field is about 10(4) V/cm and its time of changing is about 10(-12) s. This electric field initiates local mi croscale Kerr-effects thus contributing to the fluctuations of optical anis otropy, which accounts for an additional depolarized scattering.