Angular Dependence of Diffuse Reflectance Infrared Spectra. Part I: FT-IR Spectrogoniophotometer

Abstract

An optical arrangement is described which allows diffuse reflectance infrared spectra to be collected by the use of a variety of incident angles and collection geometries. In the first phase of this study, the reflectance from a nonabsorbing powder and the intensity of the reststrahlen band in quartz were monitored as a function of optical geometry. The contribution of Fresnel reflectance was found to be very dependent on optical geometry, and the effect on the intensity of absorption bands in diffuse reflectance spectra is demonstrated. Based on these preliminary results, some suggestions for minimizing Fresnel reflectance through the optimization of diffuse reflectance optics are made.