ELECTRON-EMISSION YIELD OF AL, CU AND AU TARGETS INDUCED BY FAST HYDROGEN AND HELIUM-IONS

The electron emission yield gamma ls measured for impact of H+, He+, H e2+ ions and of electrons on Al, Cu, and Au targets. The ion energy is between 0.5 MeV (H+) and 4.8 MeV (He2+), the electron energies are ar ound 1 keV. The bare ion yield is compared with predictions of a model , which assumes the yield to be proportional to the stopping power and takes collective electric fields generated by the projectiles into ac count. The He+ yield is explained by investigating the additional elec tron production of stripped electrons. It is found that the mean depth He+ ions penetrate the surface layer without losing their bound elect ron and is about 60% of the mean escape length of the emitted electron s.