The resonant charge exchange in the incoming path of alkali ions scattered at low energy from a polycrystalline nickel surface is studied by using the image effect occurring at glancing incidence (2–10° from the surface plane) and for specular reflection. The part of the experimental artefacts (geometrical factor, surface roughness…) is extracted from the reflection coefficient of almost completely neutralised projectiles (He+ or Ne+) compared with the coefficient obtained from numerical simulations (TRIM and MARLOWE codes). The present model explains very well the lowering of the reflection coefficient measured at grazing incidence (below 4°). Furthermore, the optimised values of the charge fraction in the incoming path and the image potential are in agreement with the theoretical calculations in the case of Na+/Ni at 4 keV.
View online : NIM B 193, 396-402 (2002)