Neutralization and equilibration of highly charged argon ions at grazing incidence on a graphite surface

Final-charge-state distributions of argon ions, scattered grazingly from a smooth highly oriented pyrolytic graphite surface, have been measured as a function of initial charge state (q=4--17) and impact velocity (v=0.15--0.62 a.u.) The final-charge-state distribution changes strongly with the impact velocity, but is almost independent of the initial charge state. The neutralization during grazing-angle scattering is compared to the charge-state equilibration experienced by ions passing through a solid (carbon foil), and these two processes seem to have common properties. A K x-ray spectrum from the K-shell vacancy decay of 51-KeV Ar¹⁷⁺ projectiles was obtained as a function of the angle between the ion beam and the surface. Measurements of x-ray spectra in coincidence with grazingly scattered ions are reported. A simple model for argon neutralization near and below the surface is proposed. The model assumes a direct side feeding into the Ar M shell followed by Auger and radiative L- and K-shell filling. {} 1996 The American Physical Society.