Kinetic electron excitation in the interaction of slow Kr+ ions with Al surfaces

We report experimental studies of electron emission in the interaction of 1-8 keV Kr+ ions with clean Al surfaces. We observe that total electron emission yield depends exponentially on v(-1), the inverse of the velocity of the projectiles, rather than on the inverse of the component of v orthogonal to the surface, expected in the recently proposed surface-assisted kinetic electron emission. The energy distributions of emitted electrons show well-known features of kinetic electron emission: a broad continuum background with superimposed structures due to the decay of bulk plasmons and to Auger decay of Al-2p excitations produced by electron promotion. The close correlation of the intensities of electron emission from Auger and plasmon decay with the total electron yields leads to the conclusion that kinetic electron emission in Kr+ interactions with Al surfaces is dominated by electron promotion in close atomic collisions.