The N −2( 2Π g) shape resonance in slow [formula omitted] collisions with metallic surfaces

Abstract

Metastable N 2( A 3Σ + u) molecules colliding with a metal surface can be de-excited via an Auger process in which the excitation energy of the molecule is given to an electron of the metal. We report on a theoretical study of this process for N 2( A 3Σ + u) molecule collisions on a free electron metal, Al. This de-excitation process is efficiently mediated by the formation of a transient negative molecular ion, in the present case, the well-known resonance N − 2 of 2Π g symmetry. A modelling of the electron–N 2 molecule interaction in the intermediate 2Π g symmetry allows the computation of the Auger de-excitation process characteristics: transition rate, emitted electron spectra. The present results are used to discuss the experimental results on the N 2( A 3Σ + u) de-excitation in thermal collisions on metal surfaces by Stracke et al. [Surf. Sci. 396 (1998) 212] who first proposed this de-excitation mechanism. We find this resonance mediated process to be very efficient.