Example 1 : Nitric Oxide (NO) adsorption on a Pt Surface

The sequence of spectra shown below demonstrate how IR spectroscopy can clearly reveal changes in the adsorption geometry of chemisorbed molecules. In this particular instance, all the bands are due to the stretching mode of the N-O bond in NO molecules adsorbed on a Pt surface, but the vibrational frequency is sensitive to changes in the coordination and molecular orientation of the adsorbed NO molecules.

Fig. ν(N-O) spectra obtained from a Pt surface subjected to a fixed exposure of NO at various temperatures

Note - the surface coverage of adsorbed NO molecules decreases as the temperature is raised and little NO remains adsorbed at temperatures of 450 K and above.



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