EXTINCTION AND ANGLE-RESOLVED LIGHT-SCATTERING FROM AGGREGATED METAL-CLUSTERS

Formation of particle aggregates of arbitrary size and shape by lumpin g of small particles yields extinction and scattering of light that di ffer from those of isolated particles. The aggregation process can be followed from extinction and angle-resolved light scattering measureme nts. Introducing new parameters in angular light scattering, systems c ontaining only isolated clusters were efficiently distinguished from c luster-aggregate systems. This was achieved by evaluation of the measu red data in forward and backward scattering direction and at a scatter ing angle of 90 degrees, resulting in a distinct separation of isolate d-cluster systems and cluster-aggregate systems. For measuring the ang le-resolved light scattering by noble metal colloidal particle systems , a common photogoniometer setup had to be modified. Changes in scatte ring and extinction data were qualitatively described by a model that takes into account electromagnetic coupling among clusters in the aggr egate.