ANGLE-RESOLVED UV PHOTOELECTRON-SPECTROSCOPY OF ETHYLENE AND BENZENE ON NICKEL

A review of results obtained by Angle-Resolved UV-Photoelectron Spectr oscopy (ARUPS) using linearly polarized synchrotron radiation is prese nted for two model systems, ethylene/Ni and benzene/Ni. It is shown th at for these systems detailed conclusions concerning adsorbate/substra te and adsorbate/adsorbate interactions can be derived from ARUPS spec tra using symmetry selection rules, and in combination with model calc ulations. In particular, electronic structure, bonding, orientation an d symmetry of the adsorbates in dilute and saturated layers will be di scussed. It is shown that at high adsorbate coverages lateral interact ions in the adsorbate layer play a dominant role. Steric effects in de nsely packed layers can lead to a reorientation of the molecules as co mpared to the orientation of the single molecules. The ARUPS spectra o f well ordered, densely packed layers exhibit significant (up to 2 eV) dispersion of the various adsorbate bands and allow detailed conclusi ons on two-dimensional adsorbate band structures.