Calculation of the energy loss of swift H and He ions in Ag using the dielectric formalism: The role of inner-shell ionization

The electronic energy loss of swift H and He ions in solid Ag is studied theoretically within the dielectric formalism, considering the different equilibrium charge states of the projectile inside the target. Excitation of the weakly-bound (outer) electrons is described by a superposition of Mermin-type energy-loss functions, whereas the contribution to the projectile energy loss due to the ionization of the K, L and M shells of the Ag atoms is included through hydrogenic or numerical generalized oscillator strengths. This method is used to evaluate the stopping power and the energy-loss straggling parameter of H and He ions in Ag as a function of the projectile energy, showing a good agreement with available experimental data. The contribution of the target inner-shells to the energy loss begins to be appreciable at projectile energies larger than a few hundred keV/u, being more important for the energy-loss straggling parameter than for the stopping cross section.