Resonant electron scattering by molecules adsorbed on metal surfaces: angular aspects

Abstract

The formation of a transient negative ion (AB −) is a very efficient way to transfer energy in a collision between an electron and an adsorbed molecule. It leads to the molecule excitation and fragmentation as well as to desorption processes. The AB − molecular ions correspond to well-defined electronic structures and this leads to well-defined electron angular distributions, characteristic of the ion symmetry. In the present work, we analyze in a classical approach how the electron-metal surface interaction (the polarization potential) influences the electron angular distributions. For certain symmetries, and adsorption geometries, the angular distribution is deeply modified by this interaction, which introduces a node in the distribution at 90° from the surface normal. This effect is discussed in relation with available experimental data.