Photon correlation spectroscopy of liquid interfaces. I. Liquid-air interfaces

Abstract

Photon correlation spectroscopy has been applied to the study of thermally excited capillary waves on a liquid surface. The technique of using a diffraction grating as a local oscillator has been refined for use with photon correlation; the combination has considerable advantages. Results for water compare favourably with the predictions of hydrodynamic theory over a wider range of surface wave-vector than hitherto examined. Data for glycerine agree with theoretical predictions based on a viscosity appropriate to about 1.5% absorbed water. A novel discussion of the dispersion equation of capillary waves on a liquid surface is presented.