A polycrystalline aluminum target was bombarded by He+, N+, Nef and Ar+ ions with a beam-energy of 10 or 20 keV. Two sets of photon decay curves with radiation at 308.2 and 396.2 nm, which are transitions of sputtered excited neutral aluminum, have been measured as a function of distance from the surface. The decay curve shape is interpreted as due to the photon cascade repopulation of certain AlI levels. The prominent cascade transitions are from the 4p and 4f levels to the 4s and 3d levels, respectively. Also taking photon cascades into account in analyzing the photon decay curves, the sputtered excited aluminum atoms which radiate two emission light of AlI 308.2 and 396.2 nm have about the same velocity component normal to the surface. The magnitude of the normal velocity v(perpendicular to) of the sputtered atoms is at least in the kinetic energy range around 60 eV, which is larger than the binding surface energy. (C) 1999 Elsevier Science B.V. All rights reserved.
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS