Auger de-excitation of metastable molecules at metallic surfaces

TL;DR

This paper models secondary electron emission caused by Auger de-excitation of metastable molecules at metallic surfaces, using an effective two-electron approach with Green's functions, and compares results with experimental data.

Contribution

It introduces a novel effective model for Auger de-excitation involving two active electrons and employs advanced Green's function techniques to accurately predict electron emission.

Findings

Quantitative agreement with tungsten experimental data.

Predicted electron emission for aluminum is significantly lower than other processes.

Model effectively captures the physics of Auger de-excitation at metal surfaces.

Abstract

We study secondary electron emission from metallic surfaces due to Auger de-excitation of diatomic metastable molecules. Our approach is based on an effective model for the two active electrons involved in the process -- a molecular electron described by a linear combination of atomic orbitals when it is bound and a two-center Coulomb wave when it is not and a metal electron described by the eigenfunctions of a step potential -- and employs Keldysh Green's functions. Solving the Dyson equation for the retarded Green's function by exponential resummation we are able to treat time-nonlocal self-energies and to avoid the wide-band approximation.Results are presented for the de-excitation of \NitrogenDominantMetastableState\ on aluminum and tungsten and discussed in view of previous experimental and theoretical investigations. We find quantitative agreement with experimental data for tungsten indicating that the effective model captures the physics of the process quite well. For aluminum we predict secondary electron emission due to Auger de-excitation to be one to two orders of magnitude smaller than the one found for resonant charge-transfer and subsequent auto-detachment.