What is Polarization Modulation FTIR Reflection-Absorption Spectroscopy?
Infrared reflectance spectroscopy has developed into one of the primary methods of monitoring chemical structure and molecular orientation of thin films and monolayers adsorbed onto metal surfaces. At a high (grazing) angle of incidence the intensity of a reflected p-polarized infrared light beam is enhanced at a metal surface so that even submonolayer quantities of chemisorbed species can be observed in the p-polarized FTIR reflectance spectrum. In contrast, at a high angle of incidence an s-polarized reflected infrared beam has virtually no intensity at the metal surface. This polarization disparity leads to strong selection rules at the surface, and has been used to deduce the average molecular orientation and conformation for monolayers of long chain alkyl molecules adsorbed onto metals. In addition to orientation measurements, the predominance of p-polarized light over s-polarized light at the metal surface has been utilized to obtain the differential reflectance spectrum of the a
