Quasi-elastic laser light scattering from thermally excited capillary waves on the polarised water/1,2dichloroethane interface

Quasi-elastic laser light scattering (QELS) from thermally excited capillary waves on the polarised water/1,2-dichloroethane interface was measured using optical heterodyne mixing technique. Interfacial potential difference was controlled by equilibrium partition of tetraethylammonium, tetrapropylammonium, tetrabutylammonium or tetrapentylammonium bromide. Frequency of the capillary wave of a selected wavelength was shown to decrease with the increasing electrolyte concentration. Frequency decrease was related to the decreasing interfacial tension being caused by the increasing relative surface excess of the electrolyte. No significant effect of the electrolyte concentration on the capillary wave damping was observed. Adsorption data obtained from these measurements are consistent with the results of the double layer capacity studies.