STRONG DYNAMIC DIPOLE COUPLING BETWEEN CO MOLECULES ADSORBED AT 2 DISTINCT SITES ON CU(100)

Disproportionate intensity behavior in IR absorption by CO adsorbed at two different sites on a Cu (100) surface has been examined. At saturation coverage (theta(s) = 0.57), for example, less than 5% of the CO molecules, those at the step sites, are responsible for more than 75% of the absorption intensity, while 95% of the CO molecules, those at the on-top terrace sites, account for the remainder. This anomaly arises from transition dipole coupling between the adsorbed molecules at the metal surface, and is quantitatively explained by the Persson/Ryberg model.