A reflecting microscope designed for use in front of the entrance slit of a Perkin-Elmer single-beam infrared spectrometer is described. It is shown that the heating effect of the condensed beam on the sample is not significant except in the case of compounds which absorb strongly in the 3-micron region of the spectrum, and then only if the sample is unsupported. The instrument is being applied to the study of small quantities of material in solution and to single crystals. Spectra adequate for identification purposes may be obtained from less than 10 micrograms of a sample in solution. The minimum sample size is limited at present by the technique of sample transfer and if this can be improved, spectra could be obtained with about 1 microgram. Preliminary results using polarized radiation in the study of fatty acid crystals are also presented.
A. R. H. COLE and R. NORMAN JONES, "A Reflecting Microscope for Infrared Spectrometry," J. Opt. Soc. Am. 42, 348-352 (1952)