Abstract
We report x-ray intensity fluctuation spectroscopy (XIFS) measurements of the equilibrium dynamics of colloidal suspensions of charge-stabilized spheres of radius in glycerol. The dynamics were investigated for times between 4 and several thousand seconds, and for wave vectors, , from 0.003 to 0.012 , well beyond wave vectors that can be studied with visible light. The unique advantages of XIFS for studies of concentrated suspensions composed of refractive-index-mismatched components have not previously been explored. Here, we study a dilute sample (sample I) and a concentrated sample (sample II). For sample I, the diffusion coefficient is independent of , with a value consistent with the Stokes-Einstein relation. For sample II (effective hard-sphere volume fraction, , the diffusion coefficient exhibits a minimum at the peak of the structure factor, indicating modifications to Brownian behavior due to interparticle interactions.
- Received 28 July 1997
DOI:https://doi.org/10.1103/PhysRevE.57.2030
©1998 American Physical Society