Radiation scattered by two touching spheres

During the manufacture of powder metal the size distribution of the metal spheres can be determined to some extent by the distribution of light scattered by the spheres while they are streaming by a laser beam. Micrographs show the presence of chains of spheres and of spheres with a number of smaller spheres attached to them. To model the scattered light we assume that the spheres are sparse enough to scatter light independently, an assumption that is obviously invalid for agglomerates of spheres. It is thus of interest to compare the pattern of the radiation scattered by such agglomerates with the pattern produced by isolated spheres. We use an integral equation to compute the fields scattered by two perfectly conducting touching spheres when a plane monochromatic wave is incident from an arbitrary direction. The preliminary results indicate that a small sphere attached to a large sphere changes little the RCS and that there is a significant change for two equal spheres.>