Incident angle dependence of secondary electron emission from a Ta surface by multiply charged ions

Abstract

The incident angle dependence of secondary electron emission yield γ from a clean polycrystalline Ta target has been investigated for keV Ne q+ ( q = 0−3) and Ar q+ ( q = 0−3) over the angle τ ranging from 0 to 80° to the surface normal. Generally the observed γ is found to increase as τ increases. The γ for kinetic emission of ions, γ KE, is estimated from the γ for q = 0, neutral atoms. An analysis of the incident angle dependence of γ using γ KE shows that the γ for potential emmision, γ PE, is constant. Furthermore, we concluded that the incident angle dependence of γ is due to excited atoms which are not completely relaxed into their ground state when they arrive at the surface.