Application of intensity correlation spectroscopy to the measurement of continuous distributions of spherical particles

This paper extends the formalism whereby one can obtain the parameters describing specific size distributions of spherical particles from the cumulants, which are commonly measured in intensity correlation spectroscopy, to include the Pearson III, Pearson V, Schulz, and Schulz (molecular weight) number fractions of particle radii. We demonstrate explicitly that the reduced second cumulant K2/K21 has distinct upper bounds for each of the distributions. The range of scattering angles and distributional parameters for which the Rayleigh–Gans corrections (to second order in the scattering vector q) are negligible is specifically calculated. The method is applied to data from human serum very low density lipoproteins and from narrowly distributed polystyrene latex spheres.