Depolarization of light scattered by fractal smoke clusters: An approximate anisotropic model

Experimental data on depolarization of light scattering by fractal smoke clusters are analyzed. A simple approximate model in which cluster geometrical anisotropy is simulated by a spheroidal particle, with the effective refractive index determined by the Maxwell-Garnett or Braggeman equations, is considered. The T-matrix method is used to calculate the scattering matrix of a randomly oriented ensemble of such particles. The depolarization ratio values calculated agree well with the experimental values for low aggregation degrees. Using the volume fraction (or the filling degree) of monomers as a fitting parameter, we found its dependence on the number of particles in a cluster. In agreement with the fractal scaling, this dependence turned out to be exponential; however, the value of the exponent does not coincide with the expected value 1-3/D (D is the fractal dimensionality). 34 refs., 4 figs