Photoemission observation of two molecular phases of CO absorbed on Cu(100)

The valence orbital electronic structure of CO chemisorbed on Cu(100) shows two discrete molecular phases in the sub-monolayer regime. Both 1π- and 5σ-orbitals of CO are found to interact with Cu. The more weakly bound phase of CO (not observed on polycrystalline Cu or Au) exhibits a strong reduction in the 5σ orbital bonding interaction. These results show significant differences in CO bonding on Cu, Ag or Au vs that on Ni, Pd or Pt surfaces. © 1976.