An Empirical Correction for Moderate Multiple Scattering in Super-Heterodyne Light Scattering

TL;DR

This paper presents an empirical correction method for moderate multiple scattering in super-heterodyne light scattering, enabling accurate flow and diffusion measurements in turbid suspensions with minimal complexity.

Contribution

The authors introduce a simple empirical correction technique to subtract multiple scattering background in super-heterodyne light scattering measurements, improving analysis of turbid samples.

Findings

Effective correction for multiple scattering in turbid suspensions.

Maximum electro-kinetic mobility at intermediate concentrations.

Accurate measurement of self-diffusion coefficients under various conditions.

Abstract

Frequency domain super-heterodyne laser light scattering is utilized in a low angle integral measurement configuration to determine flow and diffusion in charged sphere suspensions showing moderate to strong multiple scattering. We introduce an empirical correction to subtract the multiple scattering background and isolate the singly scattered light. We demonstrate the excellent feasibility of this simple approach for turbid suspensions of transmittance T>0.4. We study the particle concentration dependence of the electro-kinetic mobility in low salt aqueous suspension over an extended concentration regime and observe a maximum at intermediate concentrations. We further use our scheme for measurements of the self-diffusion coefficients in the fluid samples in the absence or presence of shear, as well as in polycrystalline samples during crystallization and coarsening. We discuss the scope and limits of our approach as well as possible future applications.