Applicable range of the Rayleigh-Debye-Gans theory for calculating the scattering matrix of soot aggregates.

The Rayleigh-Debye-Gans theory, though being an approximation, plays an important role in the study of light scattering by aggregates. Therefore, considerable research efforts have been invested in examining its applicable range. Past examinations were predominately performed in terms of the integrative properties (e.g., the scattering and absorption cross sections), with little work done in terms of the angular scattering properties (e.g., the Mueller scattering matrix). However, in practice, many techniques directly measure these angular properties, calling for a close examination of the theory's accuracy in predicting the angular properties. We describe such an investigation, conducted under the context of soot aggregates. The results are expected to provide useful insights into the optimal design of experiments and instruments that use light scattering for particle characterization.