Simulations and experiments on number fluctuations in photon-correlation spectroscopy at low particle concentrations

At low particle concentrations number fluctuations in photon-correlation sp ectroscopy measurements lead to a slow decay in the autocorrelation functio n, which contains information about the concentration. The characteristic t ime tau (c) of this number-fluctuation decay depends on the size of both th e particle and the scattering volume. For determination of the concentratio n a measurement should last for at least a time of 100 tau (c). Using Brown ian dynamics simulations and measurements, we have studied the effects of t he measurement time on the decay of the number fluctuations. (C) 2001 Optic al Society of America.