INVERSE PHOTOEMISSION-STUDY OF CARBON-MONOXIDE BONDING TO TRANSITION-METALS

The unoccupied CO derived bands for the densely packed CO monolayer on Ni(110), Pd(110), and Pt(110) have been investigated by inverse photoemission. In all three cases four CO derived bands can be observed in the region of the 2-pi* and 5-sigma* orbitals. For Ni and Pd the band dispersions show the signature of pi-bands. No evidence is found for unoccupied sigma-contributions, i.e. for 5-sigma donation. However, in Pt the band dispersions are significantly different and hint at a significant 5-sigma donation. The energy position of the CO derived manifold is rather similar for all three metals. These results on the electronic structure are consistent with thermodynamical and vibrational data reported in the literature for the three systems.