An infrared reflection spectroscopy study of oriented cadmium arachidate monolayer films on evaporated silver

The infrared spectra of one to ten monolayer assemblies of cadmium arachidate have been measured by glancing angle reflection spectroscopy. No frequency shifts were noted for the bands with increasing number of layers and the intensities scaled almost linearly. The observed and assigned bands exhibited a very different intensity pattern from calculated spectra based on bulk cadmium arachidate optical constants. We explain our results on the basis of oriented monolayer assemblies with the alphatic chains normal to the surface. Our data allow for a small angle of tilt of the chains away from the surface normal and suggest some twisting of the first few methylene groups adjacent to the carboxylate group. © 1982 American Chemical Society.