High energy excitations in ion-induced electron emission from AlF3

Measurements of electron emission spectra from surfaces of aluminum fluoride impacted by keV noble gas ions show a high-energy structure, peaking around 7 eV that increases in intensity with ion energy. The shape of this structure, identified by Factor Analysis, is independent of the nature and the energy of the impinging ions. We discuss one electron, two electron and plasmon excitation mechanisms and conclude that the high-energy structure results from the autoionization of F− 2p4nl n′l′ excited by electron promotion in close atomic collisions.