K-shell vacancies and residual excitation in heavy ions penetrating solids

Measurements of $K$ vacancies of F, S, and Cl ions penetrating various solids at MeV/amu energies indicate that the formation of those vacancies is well described by a simple model of competing $K$-shell rearrangement processes. Specifically, the progression at increasing penetration depth toward equilibrium vacancy fractions and the magnitudes of the fractions themselves find quantitative agreement in the model. The observation of substantial residual excitation in Cl and S at 2 MeV/amu implies that $K$ relaxation via Auger transitions is a significant post-foil charge-changing mechanism for those ions. Equilibrium effects previously taken to be due to dynamic screening by target electrons are herein attributed to the $K$ equilibrium process.