RESONANT VIBRATIONAL-EXCITATION OF N-2 MOLECULES PHYSISORBED ON A METAL-SURFACE - EFFECT OF THE MOLECULAR AXIS ORIENTATION

The vibrational excitation by electron impact of N-2 molecules physiso rbed on a jellium metal surface is studied in the low energy range dom inated by the N-g(-) ((2) Pi(g)) resonance. In order to model the effe ct of the relative orientation of the molecular axis and of the surfac e normal, we evaluated the vibrational excitation cross-sections for t he parallel and perpendicular geometries. This reveals strong symmetry and geometrical effects that are reflected in the relative strength o f the various symmetry contributions to the excitation process as well as in the differential angular distributions.