Reflection coefficient of low-energy light ions

We present a model for the slowing down and transport of light ions in the energy range between some tens of eV and some tens of keV in solids. The approach chosen here for low energies is based on the so-called age theory, and is augmented by the single-collision approximation for higher energies. These energy regimes are classified by the number of hard collision events ν experienced by the projectile before coming to rest. Technically, ν is defined as the ratio of the total range to the transport mean free path of the ion. In both the multiple- and the single-collision regimes, the particle reflection coefficient RN is shown to be a universal function of ν and cos2θ0, where θ0 denotes the bombarding angle. A simple-to-use expression for RN is derived for the entire energy range by interpolation of the two limiting cases. Good agreement is found with a large number of experimental data