Abstract
A computational scheme is presented to exactly calculate the electromagnetic field distribution, and associated radiative absorption and scattering characteristics, of large-scale ensembles of spherical particles that are subjected to a focussed incident beam. The method employs a superposition extension to Lorenz/Mie theory, in which the internal and scattered fields for each sphere in the ensemble are represented by vector spherical harmonic expansions, and boundary conditions at the surfaces of the spheres are matched by application of the addition theorem for vector harmonics. The incident field is modeled as a transverse, linearly-polarized wave with a Gaussian amplitude distribution along a fixed focal plane. Application of the method to prediction of the absorption and reflectance characteristics of particle deposits is discussed, and illustrative calculations are presented.