Reflection spectroscopy of adsorbed layers

General approximate equations are presented for the change in reflectance of a stratified medium due to the presence of an absorbing adsorbed layer. These equations, which represent reflection spectra, are simple functions of the optical characteristics of the adsorbed species. Experimental examples of monolayer spectra illustrate the sensitivity of reflection methods and the validity of the equations. Band shapes of reflection spectra differ from, but are as representative as transmission spectra. The shapes usually depend on polarization, but often do not depend on angle of incidence. Intensity is usually linear in absorption coefficient and thickness, when the approximate equations are valid.