Determination of True Infrared Absorption Frequencies from Internal Reflection Data
At the 1966 Pittsburgh Conference some measurements of the magnitudes of observed frequency differences between internal reflection bands and transmission bands were presented (1). For strong absorptions with thick films, the internal reflection minima were displaced from the transmission minima toward lower frequencies by as much as 14 cm−1. The reason for these shifts is related, of course, to the large dispersion in the refractive index coefficient and the consequent large changes in reflectivity, which do not coincide with the changes in the absorption coefficient in the vicinity of the absorption bands. Other data in the same paper suggested that, for thin films of the same materials, small frequency shifts occurred in the opposite direction, toward higher frequencies.
KeywordsDielectric Function Internal Reflection Band Shape Reflection Band True Frequency
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- 1.Robert W. Hannah, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, 1966. Google Scholar
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