Application Of An FT-Raman Accessory Interfaced To An FT-IR Spectrometer

Abstract

Raman spectroscopy is currently the focus of renewed interest due to its increasingly straightforward incorporation of near-IR laser sources and FT techniques. Conventional Raman vibrational spectroscopy provides spectral information complimentary to that obtained by IR absorption methods, thus giving the user of both techniques a more complete spectral analysis. Additionally, FT-Raman also exploits the optical throughput and wavenumber accuracy that interferometric spectroscopy offers. Still another very significant advantage results from near-IR FT-Raman's ability to obtain useful Raman spectra from compounds that would normally yield only featureless fluorescence in visible laser Raman systems. This presentation will highlight advantages that result from the coupling of a near-IR FT-Raman module with an FT-IR system. Among these is the increased sampling capability that results from the complimentary nature of the two spectroscopies. For example, although it would be nearly impossible to obtain an IR spectrum of an aqueous solution sealed in a glass tube, such a sample can be studies in quite a straightforward manner by FT-Raman spectroscopy. Also, a broad optical range is easily studied since the Raman technique allows one to observe bands corresponding to Raman shifts in the range from 3500 cm-1 down to approximately 100 cm-1 in the same scan and there is no need to change optical components. Another advantage gained by such a combined IR/Raman configuration is the resulting capability to easily switch from one technique to the other. Not only can both IR and Raman spectra be obtained routinely, but since the same data system is used by both techniques, both IR and Raman files are collected and manipulated using the same software. Thus, routines such as spectral subtraction and deconvolution can readily be applied to either technique.