The spatial coherence factor in light scattering from a system of independent particles

We derive the spatial coherence factor associated with the intensity correlation function of light scattered from N independent particles. The expression agrees with that derived by assuming a gaussian light field. We show also that the so-called cross-spectral purity condition is valid in this case. The applicability of this expression to the case of clipped intensity correlation function and to the case of strongly interacting particles are also discussed.