ELECTRONIC STOPPING BASED ON ATOMIC AND SOLID-STATE WAVE-FUNCTIONS

A review is given on single-electron mechanisms, which dominate the el ectronic energy transfer processes of light ions in gases and solids. In the case of gas targets, it will be shown that it is possible to pe rform highly accurate ab-initio stopping power calculations which cove r the range of incident energies from a few eV/u up to the Bethe regim e. First principle calculations are applied to the stopping of (p) ove r bar, H+, H-0, He2+ and Li3+ in H and He gas targets. The resulting d iscrepancies to experimental data are about 10% or less and can be att ributed to two-electron processes. Strong deviations from the usually assumed velocity proportionality at low incident energies as well as p ronounced Z(l) dependencies are found and will be discussed. Furthermo re, it will be shown that neither a single-harmonic-oscillator model n or local-density electron-gas approaches allow for a reliable predicti on of the impact parameter dependence of the mean energy transfer. In the case of solids perturbation theory is applied to the stopping of l ow energy ions in alkaline metals. These calculations include Bloch wa vefunctions of Wigner-Seitz type obtained from a Hartree-Fock-Slater c alculation and allow for a prediction of the mean energy loss under ch annelling conditions. Results of the most widely used free-electron ga s approximation will be compared to data of our more complete treatmen t. Additionally, simple scaling laws for the stopping of light ions in gases and solids may be extracted from our results.