title: X-ray photon correlation spectroscopy during homogenous shear flow.
abstract: We report x-ray photon correlation spectroscopy measurements of advective and diffusive dynamics in a dispersion of colloidal particles subjected to homogeneous shear flow in a rotating-disk shear cell. Intensity autocorrelation functions from scattering data collected using homodyne detection respond to the variation in velocity across the scattering volume when the scattering vector has a component parallel to the flow direction. Theoretical expressions for the impact of homogenous shear flow on the correlation function provide a quantitative prediction of the dependence of correlation functions on the scattering vector and shear rate. Under most circumstances, the applied shear deformation dominates the decay of the intensity correlation function. When scattering data are collected perpendicular to the flow direction, it is possible to measure the diffusive dynamics of the particles free from effects of the superimposed shear flow; however, this approach only works below some upper shear rate limit, beyond which data are affected either by shear effects (caused by the finite width of the detector) or by particle transit through the scattering volume.
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, USA. w-burghardt@northwestern.edu
authors.forename: Wesley R
authors.initials: WR
authors.lastname: Burghardt
authors.forename: Marcin
authors.initials: M
authors.lastname: Sikorski
authors.forename: Alec R
authors.initials: AR
authors.lastname: Sandy
authors.forename: Suresh
authors.initials: S
authors.lastname: Narayanan
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D056951:Photoelectron Spectroscopy / Q000379:methods*; D012212:Rheology / Q000379:methods*
chemical_list: D003102:Colloids