Intensity correlation of light scattered from hydrodynamic fluctuations

Abstract

We investigate conditions under which measurement of intensity correlation function of scattered light gives correlation functions of hydrodynamic fluctuations. We show that for a normal fluid the validy of the fluctuating hydrodynamic equations guarantees that the measured intensity correlation function is simply related to the hydrodynamic correlation functions. Even for the fluid near the critical point we show that this is true under the usual experimental condition, the so called non-Gaussian terms being too small to be observed. We then extend the same consideration to the case of clipped intensity correlation function.