Particle Sizing by Photon Correlation Spectroscopy. Part II: Average values

Abstract

Abstract The average values of the diameters and the diffusion coefficients of non‐interacting homogeneous spherical particles as obtained with photon correlation spectroscopy are reviewed. In general, the average diffusion coefficients calculated from the first cumulant can be identified as intensity averages, while the average particle diameters are harmonic intensity averages. For particles with linear dimensions that are small compared to the wavelength of light, the intensity averages can be identified as z‐averages for the diffusion coefficient and as harmonic z‐averages for the diameter. For larger particles the intensity averages are, however, different from the z‐averages and are dependent on the material examined (relative refractive index) and on the experimental equipment used (laser wavelength and state of polarization and scattering angle).