Energy loss of highly charged argon ions at grazing incidence on a graphite surface

Abstract

We have used the time-of-flight technique to measure the energy loss for 51-keV argon ions scattered grazingly from a smooth highly oriented pyrolytic graphite surface. The energy loss has been measured for several impact angles and two charge states, q=2+ and q=16+. Our data indicate that the image charge acceleration in the front of the surface, which increases the effective impact angle of the projectile, affects the energy loss. After correcting for this effect, the energy loss does not depend on the initial charge state of the projectile but increases with increasing the angle of incidence. This indicates a full neutralization of the projectile before it reaches the distance of the closest approach. The experimental results agree approximately with predictions of a modified Firsov model.