Structure and orientation of benzene and pyridine on Ir(111): Evidence for molecular distortion of benzene

Abstract

Angle-resolved UV photoemission (ARUPS) has been used in conjunction with electron stimulated desorption ion angular distribution (ESDIAD) to study the molecular structure and orientation of benzene and pyridine on Ir(111). ARUPS indicates C 3v symmetry for the benzene adsorption complex, which is interpreted in terms of a trigonal distortion of the adsorbed molecules. For pyridine a distorted C 2v symmetry is derived from ARUPS. This suggests that the pyridine molecules are adsorbed via the N atom in an upright standing geometry, with a small inclination of the ring plane with respect to the surface normal. ESDIAD specifies the tilt angle of the ring plane to ∼ 20° from the surface normal, and reveals azimuthal preference of the inclination.