Al double core electron excitation in asymmetric collisions

Abstract

Abstract We report a detailed Auger study on the double 2p electron excitation in Al by bombarding polycrystalline Al with 5–15 keV noble gas ions (Ne+, Ar+, Kr+, and Xe+) and MgxAl1 − x alloys (x = 0, 0.25, 0.50, and 0.75) with Ar+ ions. Fo resolved spectra show three well distinct narrow atomic L2-Auger peaks at ~ 76, ~ 82, and ~ 85.5 eV which exhibit clear Doppler shifts. These doubly excited Al Auger lines are detectable only for heavy noble gas ion (Ar+, Kr+, and Xe+) impact along off-normal incidence directions suggesting that the excitation occurs in the primary asymmetric collisions. However, for MgxAl1 − x alloys such atomic L2-Auger peaks are clearly present even for normal Ar+ ion incidence, unambiguously indicating that the Al double core electron excitation may also occur in collisions with lighter partners. Based on the linear dependence of the intensity of the prominent Al L2MM peak normalized to its surface concentration on the surface Mg concentration we suggest that it is due to transfer of double L-shell vacancies from one Mg atom excited in the primary Ar+Mg collision to an Al atom in a subsequent MgAl encounter through, for example, 4fσ-3dσ radial coupling.