Target inner-shells contributions to the stopping power and straggling for H and He ions ingold

Abstract

The electronic energy loss of swift H and He ions in gold is studied, paying specialattention to the contribution to the projectile energy loss due to the ionization of the targetinner-shells. We calculate the stopping power and the energy-loss straggling as a function ofthe projectile energy, taking into account the different charge states that the projectile canacquire inside the target and using the dielectric formalism. The electronic response of goldis described by the MELF-GOS model, where the excitation of valence and N-shellelectrons is characterized by a linear combination of Mermin-type energy-loss functions,whereas the contribution to the projectile energy loss due to the target K-, L-, andM-shell ionization is included through hydrogenic generalized oscillator strengths.Stopping powers and straggling are, respectively, systematically above and belowthe data in our linear response formulation when H and He ions are below0.1 MeV/u. Our calculations show that the total contribution of K-, L-, and M-shellsto stopping power and straggling is less than 0.5% and 3.5% below1 MeV/u, respectively. For stopping powers, the contribution of these inner-shells increases to 9% at10 MeV/u and continues to rise to20% at 100 MeV/u. For straggling,it increases to 23% at 10 MeV/u and rises to 35% at 100 MeV/u.