Non-linear dependence of density of elastic stopping power

Abstract

In the conventional way of calculating the energy loss of energetic particles in solid material, the target is treated as an extremely dense gas. This implies that for every collision the impact parameter distribution is given by πp 2. However, if the effective range of the interaction potential between a projectile and the target atoms is of the same order of magnitude as the average interatomic distance, this description fails, because it overestimates the influence of large impact parameters and thus overestimates the elastic stopping power. This overestimate is corrected if we describe the spatial distribution of the target atoms by the Poisson law and consider only successive interactions with target atoms in the forward directed half space, which have the smallest distance to the projectile. This results in an impact parameter distribution which favors small impact parameters and is negligibly small for impact parameters larger than the average interatomic distance, An expression for the elastic stopping power, based on this distribution is derived. Calculations for the elastic stopping power of noble-gas ions in copper are presented in the energy range of 0.1–100 keV.