Applications of Internal Reflection Spectroscopy to Surface Studies

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Abstract
Infrared internal reflection spectroscopy (IRS) has in recent years found wide use in the analysis of surfaces. Often times these have been novel applications as, for example, in the identification of stamp adhesives [l] or the observation of the spectrum of bee wings [2]. We will not attempt a review of this diverse literature but, using mostly examples from the author's laboratory, focus attention on adsorption and transport across surfaces at or below monolayer coverages. We emphasize again [31 that IRS is complementary to and, in general, not a substitute for conventional transmission IR spectroscopy [4, 51 in situations where a high area, transparent sample is available. Only for the cases of adsorption on transparent single crystals or thin films are the two techniques in direct competition. In this case multiple internal reflection provides a higher signal-to-noise ratio than would transmission because it avoids reflection and scattering losses at the film interface. Internal reflection also provides a modest amplification in the local electric field which results in an increased absorbance.