INFLUENCES OF SURFACE REFLECTIONS ON DIFFUSE REFLECTANCE MEASUREMENTS

When the diffuse reflectance of a compact, i.e. non-particulate solid sample is measured, regular reflection at the surface cannot be avoided: external reflection occurs when the sample is irradiated, and internal reflection occurs when radiation emerges from the sample. Both processes can cause severe spectral distortions of the diffuse-reflectance spectrum which seem to be particularly troublesome in the infrared range. These are discussed here along with results from calculations for the internal reflectance. © 1990.