Charge State Distributions of MeV He Ions Channeled through Thin Crystals with Atomically Clean Surfaces

Abstract

Charge state distributions of He ions transmitted through self-supporting SnTe and Au single crystals with atomically clean surfaces are measured for the energy range 0.5–2.0 MeV. Anomalous reduction of He + fraction is observed at planar channeling conditions. This is explained by the position dependent electron-loss and -capture probabilities of channeling He ions calculated from the classical Bohr and Bohr-Lindhard models. The effect of surface reconstruction on the charge state distribution is also discussed.