title: Optical extinction, refractive index, and multiple scattering for suspensions of interacting colloidal particles.
abstract: We provide a general microscopic theory of the scattering cross-section and of the refractive index for a system of interacting colloidal particles, exact at second order in the molecular polarizabilities. In particular: (a) we show that the structural features of the suspension are encoded into the forward scattered field by multiple scattering effects, whose contribution is essential for the so-called "optical theorem" to hold in the presence of interactions; (b) we investigate the role of radiation reaction on light extinction; (c) we discuss our results in the framework of effective medium theories, presenting a general result for the effective refractive index valid, whatever the structural properties of the suspension, in the limit of particles much larger than the wavelength; (d) by discussing strongly-interacting suspensions, we unravel subtle anomalous dispersion effects for the suspension refractive index.
authors.affiliation: Department of Science and High Technology, Università dell'Insubria, Via Valleggio 11, 22100 Como, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Parola
authors.affiliation: Department of Chemistry (CMIC), Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Piazza
authors.affiliation: Department of Industrial and Information Engineering, Università di Pavia, Via Ferrata 5a, 27100 Pavia, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Degiorgio