Accession Number : AD0834756

Title :   OPTICAL EFFECTS UNDERLYING THE ANALYTICAL INFRARED SPECTRA OF SOLID MATERIALS.

Descriptive Note : Technical rept. Oct-Dec 67,

Corporate Author : AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OH

Personal Author(s) : Phillippi, Conrad M.

Report Date : APR 1968

Pagination or Media Count : 37

Abstract : This treatment develops the proposition that purely optical processes are responsible for a significant fraction of the inconsistencies in the infrared 'absorption' spectra of powdered solid materials suspended in KBr or Nujol. It lays the theoretical foundation for the optical reflection and absorption processes by reviewing electromagnetic theory, the role of the optical constants of materials, and classical dispersion theory. By means of a computer parametric study, the influence of the various oscillator dispersion parameters on the optical constants and, thus, the optical properties are examined. It is demonstrated that for certain classes of materials scattering reflection losses at the surfaces of the particles dominate the form of their powder spectra, that the spectral minima are not absorption bands, and that they have no direct relation to the intrinsic oscillator frequencies. Additionally it is shown how the KBr pellet departs sufficiently from the optical film criterion that, in combination with an optical constant interaction effect found to be operating in some materials, the powerful group frequency analysis method may not be useful. Then infrared analysis is forced to resort to spectrum matching or even spectral shape matching techniques which are dependent more on perturbing optical effects and less on the fundamental properties of the material. This explanation from an optical point of view is advanced to stimulate discussion in the interface area between the chemical and physical approaches to inorganic infrared analysis. (Author)

Descriptors :   *INFRARED SPECTROSCOPY), (*POWDERS, INORGANIC COMPOUNDS, CHEMICAL ANALYSIS, MATERIALS, ABSORPTION, REFLECTIVITY, SURFACE PROPERTIES, LIGHT TRANSMISSION, INTERACTIONS, INFRARED SPECTRA, SCATTERING, FILMS, POTASSIUM COMPOUNDS, BROMIDES.

Subject Categories : Inorganic Chemistry
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE