ORIENTATION AND PERPENDICULAR ENERGY-DEPENDENCE OF DISSOCIATIVE SCATTERING OF HYDROGEN FROM CU(111)

Abstract

We report measurements of the final molecular axis orientation and kinetic energy released in the dissociative neutralization of 2.98 keV H-2+ incident at glancing angles to a Cu(111) surface. We observe two distinct structures which we correlate with scattering on two distinct regions of the potential energy hypersurface (PES) describing the interaction. The relative contribution of each of these structures to the total spectrum exhibits a threshold-like behaviour as a function of the perpendicular energy of the beam in the (nominal) range 1-2 eV. The perpendicular energy at which this threshold appears is dependent on the molecular axis orientation. We correlate this threshold with a barrier on the PES, and its dependence on orientation with an orientation dependent barrier height. The height variation is of order 0.9 eV, and the barrier is lowest for the surface-parallel axis orientation.