Low-energy electron scattering byN2molecules physisorbed on Ag: Study of the resonant vibrational excitation process

Molecules adsorbed on a metal surface can be excited by low-energy electron impact. Resonant processes in which an intermediate negative ion is formed during the collision are very efficient. The resonant vibrational excitation of ${\mathrm{N}}_2$ molecules physisorbed on Ag by low-energy electrons is studied theoretically with the coupled-angular-mode method. The influence of the neighboring surface on the excitation process (including the excitation of overtones) is analyzed. The results are compared with the experimental results of Demuth, Schmeisser, and Avouris. It is found that in a scattering experiment, most of the vibrational excitation concerns electrons that are inelastically scattered into the metal and are thus not observed experimentally.