ORIENTATION IN MOLECULE-SURFACE INTERACTIONS

The role of the orientation of a molecule in its interaction with a su rface is examined for a number of cases. At first the determination of the static orientation of a molecule at the surface is discussed. A d ependence of the orientation on state and coverage is found for O-2 mo lecules adsorbed on Ag(110). The orientation dependence of NO in chemi sorption, displacement reactions, and chemical reactions is discussed. Rotational excitation of NO in collisions with surfaces is shown to e xhibit a strong orientation dependence. Dissociative chemisorption of hydrogen molecules is found to depend on the initial orientation of th e molecule. Finally, in dissociative collisions of fast molecules with surfaces the role of the initial orientation is examined and the fina l orientation of the molecular axis is determined. Several mechanisms for molecular dissociation are discussed.