Abstract

Dynamic light scattering has been used successfully for the determination of various thermophysical properties of fluids, e.g., thermal diffusivity, sound velocity and binary diffusion coefficient. The applicability to measuring dynamic viscosities has been shown, e.g., by Brunson and Byers [1]. Basis of the measurement is the Stokes-Einstein formula

Here, η is the viscosity required and d is the hydrodynamic diameter of the spherical particles suspended. Viscosity measurements preferrably make use of monodisperse particles. Thus no integration over particle sizes is necessary. The particle diffusion coefficient D and the modulus q of the scattering vector of the optical arrangement form the decay constant in the autocorrelation function measured, τ_c = (2q²D)⁻¹. From this value η can be determined for known temperature T.

© 1992 Optical Society of America