Multiple scattering in light scattering spectroscopy

When light with a well defined frequency is scattered from a large number of small, independently fluctuating scattering centres, the resulting spectrum is 'doppler broadened'. The author examines the influence of multiple scattering processes on this broadening by using a classical expansion. The results indicate that, to second order in an expansion parameter (which is a function of the density of scatters and their polarizability), the spectrum of the scattered light is the same as that computed by using the single-scattering approximation. The effect of multiple scattering on the polarization, angular dependence and statistics of the scattered light is also discussed.