Target orientation dependence of the charge fractions observed for low-energy multicharged ions (Neq+ and Fq+) backscattered from RbI(100)

Using a time-of-flight (TOF) technique we have investigated projectile neutralization in the backscattering from RbI(100) of Ne and F multicharged ions in the keV energy range. The energy distributions and charge fractions were measured as a function of the polar incidence angle and the target azimuthal orientation. We found significant variations in the neutralization probability for the different projectiles suggesting that level matching effects play an important role. The observed scattered charge state distributions show significant dependences on both incidence and azimuth angle. These variations are attributed not only to the presence or absence of encounters with nearest neighbors, but also to the presence of more atoms lying along particular directional strings. Interpretation of the results was facilitated by carrying out detailed trajectory simulations. Sample data for few-keV F7+ and Ne8+ incident projectiles are presented to illustrate the underlying concepts.