FORWARD AVERAGE PATH-LENGTH PARAMETER IN 4-FLUX RADIATIVE-TRANSFER MODELS

The optical properties of films containing spherical particles in a no nabsorbing matrix have been modeled by using a four-flux radiative tra nsfer theory. The forward average path-length parameter takes into acc ount the different path lengths for collimated and diffuse components of the radiation field. This parameter, whose Value was known only in special cases, has been used previously as a fitting quantity. We esta blish a method for evaluating the forward average path-length paramete r in a rigorous way. Single-scattering parameters are evaluated from t he Lorenz-Mie theory, and multiple-scattering effects are taken into a ccount by means of an extended Hartel's theory. (C) 1997 Optical Socie ty of America.