The Rotational Diffusion Function in an Electric Field

Abstract

Modern electro-optic theory is built exclusively on the assumption that the variation in the optical properties of disperse systems (both molecular and colloidal) is caused by the orientation of the molecules or the particles. Practically, there are very few works where orientation not due to the interaction of the electric field with electric moments of the particles or molecules is considered. Other possible causes for orientation like electroosmosis, electrophoresis, sedimenation, convection, electric field inhomogeneities and interfacial polarizability were thoroughly discussed in the extensive review of Wilfried Heller¹ as early as 1942. Of these, interfacial polarizability (interfacial induced moment), convectional, electrophoretic,and sedimentational orientation deserve special attention. It is not excluded that in many cases of reported peculiar electro-optics effects an explanation could be found in these “non-conventional” orientation effects which, with the rare exception of the interfacial polarizability orientation, have not attracted the necessary attention and are often very easily forgotten.