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

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We present a study of the production of neon autoionizing states during glancing 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 autoionization peaks in the electron spectra indicates that the various autoionizing states fall into two main groups. At low keV energies, Ne(2p 43s 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 4nln′l′ states, whose population is aided by the motion of the projectile. Other peaks can be assigned to 2s2p 5nl, 2s2p 6nl and 2p 3nln′l′ states. A study of the effect of surface roughness shows that the production of excited states in grazing scattering is favored at rougher surfaces. For flat surfaces the peaks become broader and less intense, an effect that we ascribe to autoionization decay closer to the surface, based on previous numerical simulations of peak shapes.