Rayleigh Scattering: Collisional Motions in Liquids

Abstract

Measurements of light scattered in the Rayleigh wing were made over the range from 5 to 500 cm−1 in CCl4, C6H12, C5H12, CH3OH, C2H5OH, H2O, NH3, and CHCl3. These data when compared with earlier data on Ar, Xe, and SnBr4 indicate that in all of these liquids there is present the essentially exponential frequency dependence typical of collision induced effects. A calculation of the spectrum for large frequency shifts based on a binary interaction picture employing a Lennard-Jones potential and a short range electronic overlap distortion model agrees well with the experimental results in liquid argon. Further, assuming that molecular frame distortion is proportional to the interaction force, a similar calculation yields excellent agreement for the molecular systems. It is concluded that isolated binary interactions are mainly responsible for the spectral density in the wings of the Rayleigh spectrum.