Optical Absorption of Small Silver Spheres in Water

Abstract

Suspensions of colloidal silver spheres in water gave an absorption peak at 376 nm. The height and wavelength of the peak were altered by the adsorption of very small amounts of some materials. The changes in the absorption were accounted for very well by using concentric sphere models in which the silver spheres were enclosed in thin layers of dielectric or of absorber. The peak height of the pure material, spheres of 56-Å diameter, was substantially smaller than that predicted from bulk values of the optical constants. Much of this discrepancy was eliminated by taking account of the damping of the plasma oscillation by the presence of discrete electronic levels, as discussed by Kawabata and Kubo.