Lightscattering in Turbid Fluids

Abstract

This work is about evaluation of light scattering experiments. The static and dynamic scattering properties of polystyrene-latex samples and of a critical sample of the system 3-methyl-pyridine/water/NaBr were investigated. The scattering experiments were performed using a 3D-cross-correlation setup.Samples of high to low transmissions were investigated. In highly turbid samples multiply scattered light contributes to the scattering intensities and correlation functions. An evaluation using traditional light scattering theory, valid for transparent samples and single scattering, leads to erroneous results. Therefore it was reasonable to precisely estimate the contribution of multiply scattered light to the scattering intensities and the correlation functions.The first part of this work describes light scattering experiments of latex samples. The detector deficiencies were determined by evaluating the dependence of the amplitudes of the auto correlation functions of the polarized scattered light on the countrates. Thus it was possible to convert the experimental countrates and correlation functions into their ideal counterparts. The contributions of single and multiple scattering to the scattering intensities were calculated from the amplitudes of the 3D-cross-correlation functions. The field correlation functions of the single and of the multiple scattering were determined from the ideal auto correlation functions and the 3D-cross-correlation functions. Monte-Carlo simulations were also applied to estimate the multiple scattering contributions. The simulation results were in good agreement with the experimental data. The influence of the turbidity on the angular dependency of the single scattering volume was analysed and correction functions were presented.The second part of this work deals with Monte-Carlo simulations of the static and dynamic light scattering of the critical sample. These simulations were also in good agreement with the experimental results