CHEMISORPTIVE BONDING ON METAL-SURFACES USING PHOTOELECTRON-SPECTROSCOPY

The primary objective of any electron spectroscopic approach, when applied to the study of chemical bonding at surfaces, is to determine the detailed compositional and configurational stale of the surface-adsorbate interface. Each such state gives rise to a unique distribution in space and momentum of surface valence electrons, which largely determines the physical and chemical nature of the surface bond. In addition, chemical shifts associated with core electron levels can provide additional supportive information on the bonding mechanism. Photoelectron spectroscopy utilizing the continuously tunable, linearly polarized photon beam sources available from intense synchrotron radiation sources considerably broadens the applicability of such studies. There are some recent rather exciting applications which utilize the dependency of surface orbital ionization features on the energy and polarization of the incident radiation, as well as on the angle of detection. This review will be specifically concerned with elucidation of the bonding and orientation of simple molecules on transition metals using pholoelectron spectroscopy, particularly in conjunction with synchrotron radiation sources. Extraction of information on orbital symmetry and bond direction will be discussed, based on the use of orbital photoionization cross sections calculated for fixed molecular orientation, Emphasis will be on the chemisorplive bonding of CO, although preliminary results on other more complicated surface-molecule interactions will also be considered. © 1979.