Charge transfer dynamics of low energy oxygen ion beams scattered from Cu(001)
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We have studied the scattering of low energy O- and O+ ions off a clean Cu(001) surface in order to gain further insight into nonadiabatic electron transfer processes during reactive ion-surface collisions. For incident energies of 0.45 keV, we have measured O+/O- ratios and the absolute yields of positive, negative, and neutral oxygen atoms in the scattered flux over a wide range of scattering geometries. We have determined the extent to which memory loss occurs by comparing O+/O- ratios for single scattering events, obtained with incident O- ions and identified with a classical trajectory simulation, to those made in a similar study [C.A. Keller, A.C. Lavery, B.H. Cooper, Phys. Rev. B. 58 (1998) 10959] that was performed using incident O+ ions; The neutral and negative ions observed in the scattered flux can be explained with a simple model based on the energetics of resonant charge exchange. The presence of scattered positive ions, however, is explained by invoking a collisional mechanism for their production. (C) 1999 Elsevier Science B.V. All rights reserved.