NEAR-THRESHOLD BEHAVIOR OF THE 2P-ELECTRON EXCITATION IN MG-MG, AL-AL, AND SI-SI SYMMETRICAL COLLISIONS

Target LMM atomic Auger electron emission has been studied by low-ener gy ion bombardment on light-element surfaces. Our results show that th e threshold energies for Mg, Al, and Si 2p core electron excitation ar e the same for impact of Ar+, Kr+, and Xe+ projectiles but are substan tially lower for Ne+. A sensitive dependence of the energy onset on th e ion incidence angle has also been observed. The intensity behavior i n the near-threshold energy range is in excellent agreement with simpl e kinematic calculations using a binary-collision model and by taking into account only the first target-target symmetric encounters.