Polarization Modulation Infrared Reflection Absorption Spectroscopy: From Theory to Experiment

Abstract

Polarization modulation infrared reflection-absorption spectroscopy (PM IRRAS) is an advanced structure analyzing technique. The propagation of the electromagnetic radiation in a medium and its reflection and refraction describe the reflectivity of the incoming beam from a phase boundary and transmissivity into a second medium, respectively. When the incoming IR radiation encounters a metal surface, the IR beam is almost fully reflected from its surface. The reflectivity of the IR light depends in the state of polarization of the incoming radiation. This property gives the theoretical background of IRRAS. When the incoming IR radiation is double modulated: at the Fourier transform IR spectrometer and at a photoelastic modulator, the measured signal provides a differential spectrum which is proportional to the absorbance of the species absorbing the IR light on the mirror surface. In this chapter the theory of the propagation of electromagnetic radiation in a condensed medium and theoretical backgrounds of IRRAS, PM IRRAS and in situ electrochemical PM IRRAS are described.