Influence of surface roughness on the transmission and reflectance spectra of adsorbed species

Abstract

A model is developed for the changes in the transmission and reflection properties of an interface accompanying adsorption which takes into account explicitly the microscopic roughness characteristics of the interface. Approximate equations are derived from this model and applied successfully to data obtained for the adsorption of various gases onto vacuum deposited silver films. It is concluded that spectral information calculated from the optical changes accompanying adsorption, on the assumption that the surface is smooth, will in general be misleading, particularly so in the case of metal substrates in the visible-u.-v. spectral region. Methods for approaching this complication are discussed briefly. The possibility of characterizing the micro-roughness structure of a metal surface from measurements of reflectance changes accompanying physical adsorption is also noted.