Diffusing wave spectroscopy of uniform translational motion

Diffusing wave spectroscopy (DWS) is used to investigate the structure and dynamics of opaque (optically dense) media such as colloidal systems. These systems remain fundamentally important from both scientific and industrial viewpoints. Analyses of DWS signals from dense systems subject to flow fie lds have treated only motions due to velocity fields. Diffusive and other i nternal effects upon the particle motions are ignored. The present work pro bes the response of the DWS signal itself by using a model system in which there is no structural dynamics to obscure the motion, in a flow field wher e velocity gradients are absent. We observe initial, apparently exponential , components on the Gaussian form of the correlation function and compare t hem to strong localization of light under conditions of diffusive propagati on. For dense systems, DWS displays a time dependence, which is governed by the translational motion of the scattering system.