Multiple scattering of light in discrete random media using incoherent interactions

We consider the scattering and absorption of light in discrete random media of densely packed spherical particles. In what we term "radiative transfer with reciprocal transactions" (R²T²), we introduce a volume element of the random medium, derive its scattering and absorption characteristics using the superposition T-Matrix method (STMM), and compute its frequency-domain incoherent volume-element scattering characteristics. Using an order-of-scattering approach, we then compute a numerical Monte Carlo solution for the scattering problem with an exact treatment of the interaction between two volume elements. We compute both the direct and reciprocal contributions along a sequence of volume elements, allowing us to evaluate the coherent backscattering effects. We show that the R²T² and exact STMM solutions are in mutual agreement for large finite systems of densely packed spherical particles. We conclude that the R²T² method provides a viable numerical solution for scattering by asymptotically infinite systems of particles.