EXTINCTION OF RADIATIONS IN STERICALLY INTERACTING SYSTEMS OF MONODISPERSE SPHERES .1. THEORY

So far, the evaluation of extinction measurements has mostly relied on Bouguer-Lambert-Beer's law (BLBL), even though BLBL is known to be va lid in the limit of low concentrations only. With higher particle conc entrations, particle-particle interactions such as multiple scattering ; dependent scattering and steric interactions can lead to important d eviations from BLBL. In a discussion of the various interaction mechan isms, steric interactions are shown to be dominating in a wide and pra ctically important range of parameters. For the theoretical descriptio n of steric interactions, different complementary models are introduce d, including a statistical model, a layer model and a numerical simula tion model. The various approaches coincide to yield a simple extincti on equation in two versions, applying to the regimes of Fraunhofer dif fraction and straight ray propagation, respectively. In any case, BLBL is found as the low concentration limit of the extinction equation. A ll considerations are restricted, so far, to the case of monodisperse spherical particles.