Surface-topography dependence of line shapes in electron spectra due to decay of autoionizing states produced in inelastic ion-surface collisions

The line shapes of peaks in electron spectra due to decay of autoionizing states of Ne, formed in collisions of Ne with Al solid targets, were studied as a function of surface roughness. Strong variations in these line shapes were observed. These were modeled by taking into account the level shifts of the excited and ionic states of the atom in front of the surface and various resonant and Auger capture and loss processes. It is shown that rather complex line shapes may be expected. The electron spectrum generally possesses a peak at energies in the vicinity of that corresponding to autoionization of a free atom, as well as a high-energy tail and a secondary maximum. The intensity of the secondary maximum depends on how close to the surface most excited atoms decay and hence depends on surface flatness.