We report on measurements of scattered projectile angular and charge state distributions for 3.75 keV/amu ${\mathrm{O}}^{q+}$ $\left(3\le q\le 8\right)$ ions surface channeled along the $〈1\overline{1}0〉$ direction of a Au(110) single crystal target. Projectile trajectory calculations indicate that the projectiles spend less than 30 fs within 2 Å of the topmost Au surface layer. Nevertheless, almost complete charge equilibration is observed in the scattered projectile charge state distributions. It is concluded that, already at the target interface, strong screening effects are present which make possible direct capture to the projectile L and M shells in relatively large impact parameter collisions.

• Received 6 September 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.2204