Velocity dependence of azimuthal anisotropies in ion scattering from rhodium {111}

The scattering of He⁺, Ne⁺ and Ar⁺ ions from Rh {111} is measured as a function of the azimuthal angle of the primary ion for an incident polar angle of 70° from the surface normal and an inplane collection angle of 60°. In this case anisotropy is defined as the ratio of the yield of ions scattered having the azimuth of 〈110〉 to the yield of those having the azimuth of 〈211〉. The yield ratio for all particle types correlates with particle velocity. The ratio is ∼ 1 at low velocities, decreases to ∼ 0.2 at 8 × 10⁶ cm s and then increases to a value of 1.4 at 25 × 10⁶ cm s. Molecular dynamics calculations have been performed for Ne⁺ ion scattering from Rh{111} in order to understand the changes in anisotropy with particle velocity. Qualitative agreement with the experimental results is obtained without having to account for neutralization. A neutralization probability that depends on the collision time improves the agreement between the calculated and experimental yield ratios. A velocity dependent probability will not affect the ratio of yields in two different azimuthal directions.