Secondary electron emission due to Auger de-excitation of metastable nitrogen molecules at metallic surfaces

With an eye on plasma walls we investigate, within an effective model for the two active electrons involved in the process, secondary electron emission due to Auger de-excitation of metastable nitrogen $N_2(^3\sigma^+_u)$ molecules at metallic surfaces. Modelling bound and unbound molecular states by a LCAO approach and a two-center Coulomb wave, respectively, and the metallic states by the eigenfunctions of a step potential we employ Keldysh Green's functions to calculate the secondary electron emission coefficient $\gamma_e$ retaining for the Auger self-energy the non-locality in time and the dependence on the single particle quantum numbers. For the particular case of a tungsten surface we find good agreement with experimental data indicating that the relevant Auger physics is well captured by our easy-to-use model.