Non-reactive orientations of molecules at surfaces

The role of the orientation of a molecule in its interaction with a surface is examined for the specific case of NO interaction with Pt(111). For this system molecular chemisorption occurs, mediated by a strong chemisorption well. Experimental results concerning sticking, angular distributions of scattered molecules, steric effects in scattering, and rotational excitation will be presented. Classical trajectory calculations using a model potential energy hypersurface can reproduce most experimental findings. Analysis of the trajectories shows that there is a strong orientation dependence of rotational excitation and sticking. The O-end of the molecule turns out to be non-reactive. The N-end of the molecule is very reactive. Its behaviour can almost be described using statistical methods.