Compressed CO absorption layers on the (110) surfaces of Ni, Pd, and Pt : An inverse photoemission study of the unoccupied electronic band structure
The unoccupied band structure of a CO monolayer on Ni(110), Pd(110) and Pt(110), respectively, has been investigated by inverse photoemission. For Ni and Pd the CO-derived band structures exhibit only marginal differences. The observed bands are interpreted in terms of 2pi(x)- and 2pi(y)-derived CO-CO bonding and antibonding bands. The level ordering in the centre of the surface Brillouin zone, as obtained from a polarisation analysis, revealed a similar splitting for the 2pi(x) and the 2pi(y) levels at normal incidence. This indicates a CO-CO interaction of approximately the same magnitude in the x as well as the y direction. Consequently, the CO molecules seem to be arranged in a nearly hexagonal structure at monolayer coverage, which in turn is due to the CO-CO repulsion dominating over the CO-substrate interaction in the tightly packed monolayer. The observed level ordering of the 2pi(y) bands is consistent with such a geometry. On Pt(110), a distinctly different electronic structure indicates a different bonding of the CO to the metal substrate, namely a reduced 2pi backbonding and a more prominent role of the 5 sigma dative bonding. This may also give rise to a slightly different absorption geometry.
Bibliographic Reference: Article: Chemical Physics, Vol. 177 (1993) pp. 337-348
Record Number: 199410014 / Last updated on: 1994-11-28
Original language: en
Available languages: en