Ellipsometric light scattering for the characterization of thin layers on dispersed colloidal particles.

The thin interface layer on colloids in a liquid can be characterized by applying nulling ellipsometry to a scattering experiment. Close to 90 degrees scattering angle the ellipsometric quantities tan(Psi) and Delta of particles smaller than the wavelength behave like at the Brewster angle of reflection ellipsometry. The minimum of tan(Psi) and the slope of Delta depend on thickness and refractive index of the layer, while the location of the minimum is sensitive to the refractive index of the particle. As an example, the swelling of a thermosensitive layer on colloidal particles has been determined from measurements at two wavelengths.