Influence of the description of the target energy-loss function on the energy loss of swift projectiles

The optical energy-loss function (ELF) of Au and Al, obtained from experiments, is extended to finite wavenumber k using three different widely used models, namely, with the Mermin type ELFs with generalized oscillator strengths (MELF-GOS) model, the extended Drude model and the Penn model. The resulting ELFs show important differences but the MELF-GOS model gives more realistic results when compared with the available experimental ELFs for finite k. These differences affect calculations of important parameters in projectile-solid interaction. The calculated stopping power and energy-loss straggling of Au and Al for H projectiles as well as the corresponding inelastic mean free path (IMFP) of electrons in Au and Al clearly show that the results depend on the model used for the ELF description. Comparison with experimental data gives support to the MELF-GOS model, especially in a material with a complex energy-loss spectrum such as Au. Copyright (C) 2008 John Wiley & Sons, Ltd.