An Experimental and Theoretical Study of the Infrared Reflectance of Thin Oxide Films on Metals

External reflectance infrared spectroscopy has been used to study the formation of oxide films on chromium and iron alloys. Experimental data have been acquired with an FTIR spectrometer using a polarized beam at high angles of incidence to the surface normal. Theoretical calculations have been made for these systems and are compared with the experimental results. Particular attention is given to the quantitative calculation of film thickness. Complications which arise from distortions in band shape, frequency shifts, the appearance of additional reflectance minima, and beam divergence and state of polarization are discussed in detail.