Carbon monoxide chemisorption on a nickel surface: An investigation of unoccupied bands

Unoccupied bands of the Ni(110)/CO(2×1)p2mg chemisorption system were investigated by k-resolved inverse photoemission and by tight-binding extended-Ḧckel calculations. A detailed symmetry analysis reveals the effects of metal-CO backbonding in the CO 2 derived manifold. The CO 2-metal sp interaction, although comparable to the d interaction of some CO 2 bands, effects the band topology only weakly and in a rather uniform manner. This study provides the first quantitative assessment of the CO 2-metal d and sp interaction based on measurements of unoccupied bands.