Electron Emission and Electronic Stopping in the interaction of slow helium ions with aluminum

We address the question of the non-linearity of the electronic stopping power of slow helium ions in aluminum by measuring energy distributions and yields of electron emission under the impact of 0.2-4.5 keV 3He+ and 4He+ ions. Electron emission experiments can provide an alternative point of view to resolve controversial issues often arising in stopping power measurements. The comparison between two isotopes allows to distinguish between energy and velocity dependent emission mechanism and indicates that reported non-linear velocity dependence of electronic stopping power can be attributed to residual nuclear stopping effects.