Dynamic Depolarized Light Scattering

Abstract

Most photon correlation experiments, as may be determined from a perusal of the articles in this book, measure time correlation functions of the polarized scattered light. The depolarized scattered light is, however, a rich source of dynamic and structural information which is often not readily obtainable by other techniques. The major reason for this relative neglect of the depolarized scattering is that depolarized signals are often much less intense than polarized signals and are thus often obscured by interfering signals due to optical imperfections in lenses and cells, multiple scattering, polarizer leakage, and solvent scattering. In addition, as will be described in somewhat more detail below, the depolarized time correlation functions often decay on a fast time scale (a few microseconds), rendering photon correlation difficult because of phototube afterpulsing and the signal-to-noise problems encountered when the scattered signals display a small number of photons per correlation time. Of course, correlation functions which decay on the nanosecond or faster time scales may usually be obtained by measuring the spectral distribution of the scattered light intensity using a Fabry-Perot interferometer as a monochromator. A troublesome regime occurs in the region approximately between 0.05 and 1 /μsec where both Fabry-Perot interferometry and photon correlation are difficult.