INFRARED OPTICAL-PROPERTIES OF DIELECTRIC METAL LAYER STRUCTURES OF RELEVANCE TO REFLECTION ABSORPTION-SPECTROSCOPY

The reflection of mid-infrared (IR) radiation from a non-absorbing (dielectric) layer of varying thickness on a semiinfinite metallic substrate is modeled using the classical Fresnel relations. Reflectance, phase shift, and field intensity are calculated as functions of polarization and angle of incidence. An ultrathin layer of an IR-absorbing molecule is then included in the model and the magnitude of the reflection absorption band calculated. The results provide insight into the design of experiments in which a metal layer buried beneath the surface of a dielectric material is used to enhance sensitivity to adsorbates in external-reflection IR reflection absorption spectroscopy.