Resonant charge transfer at dielectric surfaces

TL;DR

This paper provides a theoretical model for secondary electron emission caused by resonant charge transfer during metastable nitrogen molecule collisions with dielectric surfaces, highlighting the efficiency of electron capture and decay processes.

Contribution

It introduces a combined theoretical approach using Keldysh Green's functions and rate equations to describe electron capture and decay during surface collisions, with specific calculations for various dielectric materials.

Findings

Electron capture is highly efficient during collisions.

Natural decay dominates over surface-induced decay.

Emission coefficients are around 0.1 for most materials.

Abstract

We report on the theoretical description of secondary electron emission due to resonant charge transfer occurring during the collision of metastable nitrogen molecules with dielectric surfaces. The emission is described as a two step process consisting of electron capture to form an intermediate shape resonance and subsequent electron emission by decay of this ion, either due to its natural life time or its interaction with the surface. The electron capture is modeled using the Keldysh Green's function technique and the negative ion decay is described by a combination of the Keldysh technique and a rate equation approach. We find the resonant capture of electrons to be very efficient and the natural decay to be clearly dominating over the surface-induced decay. Secondary electron emission coefficients are calculated for aluminum oxide, magnesium oxide, silicon oxide, and diamond at several kinetic energies of the projectile. With the exception of magnesium oxide the coefficients turn out to be of the order of 0.1 over the whole range of kinetic energies. This rather large value is a direct consequence of the shape resonance acting as a relay state for electron emission.