Electron yield from Be-Cu induced by highly charged Xeq+ ions

The total electron yield, γ, for emission of electrons induced by impact of Xeq+ (8≤q≤28) ions with kinetic energy per charge Ei/q from 5 to 150 keV/q on clean Be-Cu is presented for the impact angle, θ, ranging from 0 degree sign to 60 degree sign . The θ-dependencies are analyzed with the use of the relation γ(θ)=γabove+γbelow/cosθ which can distinguish above- and below-surface electron emission. Fits of experimental data to this relation give a ratio γbelow/γabove<1 for q>14 and given range of Ei/q. The analysis also shows that the above-surface electron yield, γabove, is proportional to the charge state and the below one, γbelow, increases with increasing ion impact velocity