Optical properties of fractal clusters

Abstract

Optical scattering and absorption characteristics of fractal clusters are calculated with a self-consistent scheme in which the multiple scattering and local field effects are treated exactly in the dipole approximation. Our results indicate that for optical scattering the gold colloidal aggregates with fractal dimension D = 1.75 behave essentially as low dimensional objects and therefore can be accurately described by the (single-scattering) Born approximation. However, the absorption spectrum of the clusters is shown to be significantly affected by the proximity of the gold particles to their nearest neighbors in the aggregate structure. Comparison with experimental data is shown.