Electron emission in collisions of slow rare gas ions with partially cesiated W (110)

Abstract

Abstract.We report the spectra of electrons emitted after slow collisions (50 eV) of rare gas ions (He +, Ne +, Ar +, and Xe +) with partially cesiated W(ll0) surfaces. The electron spectra are discussed in terms of the two interatomic Auger processes, Auger Capture and Auger Deexcitation and the intra-atomic Auger process, Autodetachment of Rg-* (He-*(1 s 2s 2 28) in the case of He). Model calculations including these processes can qualitatively reproduce the measured spectra as well as experimental values for the electron emission coefficients, 7. This is demonstrated for collisions of He + ions and thermal metastable He atoms with clean and partially cesiated W(110).

Electron kinetics at the plasma interface

“…The secondary electron emission coefficient is the value of γe (orange solid line) at the end of the outgoing branch. It is in good agreement with experimental data [67].…”

“…The probability for emitting a secondary electron in the course of the collision is γ e (t max ) ≈ 0.2 which agrees surprisingly well with experimental data by Müller and coworkers [67]. Despite the simplicity of the model and the uncertainties arising from the Gadzuk construction [57,58] we use for obtaining the matrix elements of the Hamiltonian (10), we nevertheless obtain very good results.…”

“…It is of course not a hard test of the viability of the semiempirical approach. For that we should at least be also able to reproduce experimental data [67] for inert gas ions other than He + (1 2 S 1/2 ). Work in this direction is in progress.…”

“…The parameter setting is not appropriate for a He + (1 2 S 1/2 ) ion scattering off a plasma wall where the incident would be normal and not grazing because of the sheath potential. However, the ion beam scattering experiments from which we obtained data for secondary electron emission coefficients have been performed for grazing incident [67]. To compare our results with measured data we hence use this scattering geometry.…”

Quantification of surface charging memory effect in ionization wave dynamics

“…In fact, in the experimental study of Tschiersch et al 66 , the effective secondary electron emission coefficients for different dielectric materials have been reported to be between 0.02 and 0.4. Values of that order have been calculated theoretically through solid-state considerations for dielectric surfaces 67 and through quantum-kinetic methods for metallic surfaces 68 , as well as measured for metallic surfaces 69 . The surface charge density on the surface of the dielectrics is obtained by integrating charged particle fluxes to the surface in time.…”