Recording Spectra of Adsorption Systems

Laser Raman spectroscopy as it is applied to the study of surface adsorbed.species involves a number of experimental problems such as fluorescence, weak Raman lines, and interfering plasma lines. Techniques of overcoming these problems have been continually improved and good 

(a) Raman spectrum of a pretreated Cab-O-Sil disk recorded using a laser beam expander (b) infrared spectrum of a newly pressed Cab-O-Sil disk. From Hendra and Gilson, Laser Raman Spectroscopy, p. 186. Wiley, New York, 1970. 

Raman spectra can now be obtained of numerous adsorbate-adsorbent systems. 

The Raman spectrum of an oxide sample after adsorption may be considered to consist of the spectrum of the adsorbed species superimposed on the spectrum due to the oxide adsorbent. In general, the Raman spectra of oxide adsorbents are sufficiently weak or sufficiently simple that they allow the detection of Raman lines due to the adsorbed species. This is one major advantage of Raman scattering over infrared absorption spectroscopy. The infrared spectra of most oxide adsorbents show strong absorptions which may obscure those arising from the adsorbates (Figs. 13,14). 

Other explanations have been offered for the unusually high spectral background encountered in high surface area oxide materials. Buechler 

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