Reflection Spectroscopy With The FT-IR Microscope

William T. Wihlborg; John A. Reffner; Scott W. Strand; Frank M. Wasacz

doi:10.1117/12.969473

1 December 1989 Reflection Spectroscopy With The FT-IR Microscope

William T. Wihlborg, John A. Reffner, Scott W. Strand, Frank M. Wasacz

Proceedings Volume 1145, 7th Intl Conf on Fourier Transform Spectroscopy; (1989) https://doi.org/10.1117/12.969473
Event: Seventh International Conference on Fourier and Computerized Infrared Spectroscopy, 1989, Fairfax, VA, United States

Abstract

The FT-IR microscope is a versatile sampling accessory used to record IR spectra in either transmittance or reflectance modes and capable of obtaining data from microscopic sampling areas. Because the FT-IR microscope simplifies the collection of reflectance data it has renewed interest in reflectance spectroscopy. Moreover, the ability to see the specific sample and to obtain spectra from small areas makes it possible to differentiate the mode of the reflection data. Reflections can be specular, diffuse or reflection-absorption modes. These modes are not independent, but the sample and its surface geometry can cause one mode to dominate all others. With polished grains or single crystal faces, specular reflection is the dominate mode. Thin films on metallic reflecting substrates make reflection-absorption the major reflection mode. Diffuse reflection dominates when the surface is very rough or fine irregular particles are analyzed. Since the sample can be seen with the microscope, the reflection mode can be predicted by direct observation of the sample's surface. In this work, examples of reflection spectral measurements are presented to illustrate the versatility of the FT-IR microscope. Of particular interest is the first report of quantitative analysis of a copolymer using specular reflectance measurements obtained with the FT-IR microscope. In this analysis, the Kramers-Kroenig transformation was used to obtain extinction (k) values. The k values derived from specular reflection are quantitative agreement with absorbance values measured by transmission.

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William T. Wihlborg, John A. Reffner, Scott W. Strand, and Frank M. Wasacz "Reflection Spectroscopy With The FT-IR Microscope", Proc. SPIE 1145, 7th Intl Conf on Fourier Transform Spectroscopy, (1 December 1989); https://doi.org/10.1117/12.969473

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