Secondary-electron yield from Au induced by highly charged Ta ions

The total electron yields, γ, for the emission of electrons induced by the impact of Taq+ (11≤q≤41) ions with kinetic energy per charge from 15 to 150 keV/q on clean polycrystalline Au are presented. The experimental data are analyzed with use of the relations γ(θ)=γ(0) cos-fθ and γ(θ)=γabove+γbelow cos-1θ. Fits of experimental data give a range of f from ∼0.6 to ∼0.17 and ratio γabove/γbelow>1. The analysis also shows that the above-surface electron yield, γabove, strongly depends on the charge state (γabove∼q) and the below one, γbelow, is proportional to the ion impact velocity (γbelow∼v). The correction of cos-1θ-dependence for fit improvement is discussed