DEPOLARIZED LIGHT-SCATTERING FROM FRACTAL SOOT AGGREGATES

We have measured the depolarization ratio rho of light scattered from three different premixed hydrocarbon-oxygen flames. The soot clusters in these flames are well described as fractals with a dimension of 1.7 9+/-0.10. We show that the depolarization is due to intracluster multi ple scattering. We also show that rho similar to N--0.6, where N is th e number of monomers per cluster for scattering in the forward directi on. We created simulated diffusion-limited-cluster-aggregate clusters on a computer and used a self-consistent electric-dipole-induced-dipol e calculation to calculate rho and again find rho similar to N--0.6. T he calculated magnitude, however, is too small; various modifications are tried or suggested to bring about a quantitative agreement of theo ry and experiment.