Velocity dependence ofKLLAuger emission from hollow atoms formed during collisions of hydrogenicN6+ions on surfaces

This paper presents a detailed description of KLL Auger spectra arising from collisions of hydrogenic ${\mathrm{N}}^{6+}$ ions on clean Si(100) and Al(110) surfaces at energies ranging from 78 eV up to 60 keV and at incident angles from 2.5° up to 45°. Atomic structure calculations of KLL Auger energies and decay rates for hollow atoms, together with simulations of the projectile trajectories, support a model in which the de-excitation of the ions proceeds essentially via two mechanisms. Before the ion enters the ‘‘close collision range,’’ a few of its L-shell vacancies are filled by Auger cascades involving outer shell electrons. But as seen as the projectile suffers close collisions, L-shell vacancies are rapidly filled by direct capture of target core electrons. The time scale of the latter mechanism is determined by the collision frequency.