Optical Absorption Produced by Silver Particles in Glass and by Sodium Particles in a Sodium Chloride Matrix

Abstract

The optical absorption produced by small silver particles in stained glass and by sodium particles in sodium chloride is calculated as a function of the particle size. The calculations are made using the theory of Mie modified according to the model of Kreibig and Fragstein to allow for the scattering of the conduction electrons of the metal by the particle surface. The results agree well with the measured spectra from silver particles, whose size was measured by electron microscopy, except that the position of the measured absorption peak for smallest size particles occurred at longer wavelength than the calculated position. Comparison of the calculated absorption spectra for sodium particles with the measured X band in additively coloured sodium chloride suggest very strongly that the X band is colloidal and a tentative mechanism for the growth of the particles is proposed.