Ellipsometric investigation of black soap films

Abstract

Thin soap films of sodium dodecyl sulphate and sodium dodecyl benzenesulphonate have been studied with a combination of ellipsometry and reflectometry. It is demonstrated that an optical three-layer model is superior to a one-layer model for the interpretation of the ellipsometric data. The refractive indices of the film core and the surface layers are determined, and it is found that the index for the surface is higher than that for the film core. The composition of the Newton type of film is discussed on the basis of these data.