Infrared Multiple Specular Reflectance of Mono- and Submonomolecular Layers of p-Bromobenzoic Acid on Oxidized Metals

Abstract

The advantages of Multiple Specular Reflection (MSR) over single reflection grazing incidence infrared spectroscopy are discussed in this paper. A calculation which incorporates the experimental constraints for a multiple reflection setup is performed. The results concerning the angular dependence are confirmed by experiment. The main advantages are a wide angular acceptance and a release of the grazing angle of incidence geometry. Approximately the same sensitivity can be obtained as is theoretically possible with a single reflection at grazing incidence. However, in practice a somewhat higher sensitivity can be obtained with multiple specular reflectance spectroscopy. The sensitivity is illustrated by the measurement of submonolayers of p-bromobenzoic acid chemi-sorbed on an oxidized aluminium flat surface. Comparison with neutron activation analysis data shows that the reflection-absorption intensities are proportional to the surface coverage. A dependence of spectral features on surface coverage can be observed.