Optical extinction by spherical particles in an absorbing medium: Application to composite absorbing films

The optical extinction rate of the particle embedded in an absorbing host is defined as a rate of local energy losses caused by the particle (absorption in the particle volume and scattering by the particle-matrix interface) referenced to the matrix background. The rate of scattering and absorption by the particle is calculated via integration of the appropriate Poynting vectors over the particle surface. The explicit expressions for the optical extinction and scattering rates by the spherical particle are derived. A heuristic approach to relate the local energy losses to the macroscopic extinction coefficient of the thin absorbing film with uniformly distributed embedded particles is presented. The method is applied to calculate the optical response of iron clusters embedded in a fullerite film. The calculated optical extinction coefficient of the system shows a good agreement with the overall features of experimentally obtained spectra.