RESUMO
Dynamic light scattering experiments have become a powerful tool in order to investigate the dynamical properties of complex fluids. In many applications in both soft matter research and industry so-called "real world" systems are subject of great interest. Here, the dilution of the investigated system often cannot be changed without getting measurement artifacts, so that one often has to deal with highly concentrated and turbid media. The investigation of such systems requires techniques that suppress the influence of multiple scattering, e.g., cross correlation techniques. However, measurements at turbid as well as highly diluted media lead to data with low signal-to-noise ratio, which complicates data analysis and leads to unreliable results. In this article a multiangle regularization method is discussed, which copes with the difficulties arising from such samples and enhances enormously the quality of the estimated solution. In order to demonstrate the efficiency of this multiangle regularization method we applied it to cross correlation functions measured at highly turbid samples.
RESUMO
The evaluation of conventional light-scattering experiments in turbid media is often highly complicated because of the presence of multiple scattering contributions. The three-dimensional (3-D) cross-correlation method presented provides an effective and handy method to suppress the influence of multiply scattered light. As the time dependence of the 3-D cross-correlation function is determined solely by the singly scattered light, the evaluation of the decay constant yields reliable values for the effective diffusion coefficient and the hydrodynamic particle size of the suspended particles. Furthermore, analysis of the amplitude of the 3-D cross-correlation function permits the determination of the differential scattering cross section even for highly turbid suspensions.
