ASYMMETRIC LINES AND BACKGROUND SHIFTS IN REFLECTION-ABSORPTION INFRARED-SPECTROSCOPY

The approximations commonly used in interpreting infrared spectra of adsorbates on metal surfaces neglect the dielectric response of the metal. At high angles of incidence, these approximations can be inadequate, particularly on low-conductivity metals. Straightforward analytic expressions are presented that are valid at all angles. The dielectric response produces an asymmetric line shape even for a Lorentzian oscillator, reduces the intensity of the band, and slightly enhances the broadband reflectance of the surface.