Kinetic electron emission from Al surfaces by slow ions

We measured energy distributions of electrons emitted in the interaction of Na+ with Al surfaces at incidention energies in the range 150–4000 eV. The data allow to correlate emission intensities with spectral signaturesof electron excitation processes. We find a remarkable contribution to electron emission from asymmetriccollisions between incoming ions that have survived neutralization at the surface and target atoms, leading toAl-2p excitation via a vacancy transfer process. We observe that the total electron emission yields sharpincreases by more than an order of magnitude at impact energies above the threshold for this process.