Number Fluctuations of Polydisperse Scatterers

Abstract

The intensity statistics of incoherently detected light scattered from fluctuating numbers of polydisperse scatterers undergoing brownian motion are discussed. General formulae are developed for the normalized moments of the intensity distribution and normalized intensity correlation functions. A relationship between the variance of any finite duration measurement of a normalized moment and the higher-order correlation functions is also obtained. This error is evaluated up to the fourth normalized moment. Theoretical moments and errors are then compared with measurements on polydisperse polystyrene latex samples. Although agreement between theory and experiment is good, it is clear that any measurement of polydispersity by this technique can be only relative.