Single versus double 2p excitation in neon projectiles scattered from surfaces

We scattered 0.45–5 keV Ne+ ions at Al surfaces, performing angle resolved measurements of electron spectra from autoionizing decay of excitations in the scattered projectiles, produced by electron promotion in close atomic encounters with target atoms. The shift and the broadening of the autoionization lines due to the motion of the emitting atoms in vacuum show that the double 2p excitation in neon projectiles occurs simultaneously in a single scattering event and not in two consecutive collisions, as commonly assumed. Implications of our findings are commented upon for their relevance in research on charge exchange and energy deposition in ion-solid interactions, which are expected to be of interest for many fields.