Analysis of intensity correlation spectra of mixtures of polystyrene latex spheres: A comparison of direct least squares fitting with the method of cumulants

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Abstract
This paper presents a comparison of direct least squares fitting with the method of cumulants for the analysis of intensity correlation spectra of a mixture of two sizes of polystyrene latex spheres of diameter ratio 1:2. It is demonstrated that both methods lead to mean values of the particle diameters and scattering amplitude ratio which agree with each other within about 5% or less. However, the cumulant analysis depends critically on the choice of the coincidental background for its success. It is observed that for the type of correlation function involved in this study, the formulas necessary to calculate the parameters mentioned above from the cumulants can result in substantial error propagation. Therefore, the cumulants must be known with high precision in order to avoid large uncertainties in the results.