Formation of autoionizing Ne** in grazing collisions with an Al(111) surface

We present a study of the production of neon autoionizing states during gla ncing scattering of 3-50 keV Ne+ on an Al(111) surface of varying degree of roughness. The projectile energy dependence of the intensity of neon autoi onization peaks in the electron spectra indicates that the various autoioni zing states fall into two main groups. At low keV energies, Ne(2p(4)3s(2)) autoionizing states are formed, while at higher energies other peaks appear in the electron spectra with similar intensity. Some of these peaks may be due to low-lying 2p(4)nln'l' states, whose population is aided by the moti on of the projectile. Other peaks can be assigned to 2s2p(5)nl, 2s2p(6)nl a nd 2p(3)nln'l' states. A study of the effect of surface roughness shows tha t the production of excited states in grazing scattering is favored at roug her surfaces. For flat surfaces the peaks become broader and less intense, an effect that we ascribe to autoionization decay closer to the surface, ba sed on previous numerical simulations of peak shapes. (C) 2000 Elsevier Sci ence B.V. All rights reserved.