IDENTIFICATION OF A SURFACE-REACTION PRODUCT BY DETECTION OF A VIBRATIONAL COMBINATION BAND

NCO molecules formed by the reaction of adsorbed CO and nitrogen atoms are unambiguously identified by means of infrared absorption spectros copy. This identification of a surface reaction product is achieved by the detection of the combination band of two intramolecular modes. Is otopic substitution experiments using (CO)-C-12-O-18 and (CO)-C-13-O-1 6 are used to confirm the mode assignments through the unequal shifts of the various vibrational modes. The intermode anharmonicity is accur ately determined to be 25.5-26 cm(-1) which establishes the first reli able number of this type for an adsorbate species.