Unoccupied molecular orbitals of aromatic hydrocarbons adsorbed on Ag(111)

Publisher Website
Google Scholar
Abstract
The unoccupied π* bands of epitaxial overlayers of benzene, naphthalene, anthracene, tetracene, perylene, and coronene on a Ag(111) surface have been studied by angle resolved inverse photoemission spectroscopy. A comparison with HAM/3 MO calculations and electron transmission gas phase measurements enables the assignment of the π* affinity levels of these organic systems. In conjunction with previous angle resolved photoemission, optical absorption, and near edge x‐ray absorption studies a complete picture of their valence band structure and morphology evolves. Optical and x‐ray absorption excitation energies are discussed in the light of the experimentally determined one‐electron correlation diagram. Gas phase–solid relaxation energies of the affinity levels are found to decrease in the series of benzene to tetracene (1.7→0.5 eV) attributed to the increasing size of the involved molecular orbitals. For benzene a low lying σ*‐shape resonance has been identified in the isochromat inverse photoemission spectrum.