Toward a universal extinction spectrum of self-affine silver colloid clusters: Experiment and simulation

Polarized extinction spectra of large fractal aggregates of colloidal silve r deposited gravitationally onto a quartz substrate were measured by transm ission as a function of angle of incidence. The spectral components tangent ial and normal to the average plane of the clusters compacted along the dir ection of deposition were extracted from these and compared with spectra ca lculated from simulated fractal aggregates that were projected onto a plane . The two sets agree acceptably, suggesting that the normal and tangential spectral components represent "universal,'' i. e., size-independent extinct ion spectra characterizing all (compacted) cluster-cluster aggregates of co lloidal silver. (C) 1999 American Institute of Physics. [S0021-9606(99)7141 4-5].