Fermi density effect on the stopping power of metallic aluminum

The density-effect correction δ to the Bethe stopping-power formula for fast charged particles is evaluated for metallic aluminum from the dielectric-response function ε(E). The latter has been accurately determined over the entire range of excitation energy E by Shiles, Sasaki, Inokuti, and Smith through comprehensive analysis of all pertinent experimental data. The resulting values of δ (which is a function of the particle speed βc) should be the most reliable to date. The present result agrees well with that of Sternheimer, who used a simpler and less rigorous procedure, and thus corroborates the general view that δ is insensitive to fine details of the behavior of ε(E). We also present general remarks on the evaluation of δ and on the analytic continuation of ε(E) as a function of the complex energy E.