Measurements of Inelastic Energy Loss in Atomic Collisions of Al+, P+, S+, Cl+, Ar+, K+, and Mn+ on Argon at keV Energies and Large Scattering Angles

Abstract

The inelastic energy-loss distribution $Q$ has been measured for single large-angle collisions between argon atoms and incident projectile ions with atomic numbers $Z_1$ ranging from 13 to 25. The data are obtained by measuring the energy and scattering angle of the scattered incident particle. This method provides well-resolved $Q$ spectra, being almost undisturbed by thermal target motion. In all cases studied, the $Q$ value exhibits a sudden change and a triple-peaked structure in a narrow range of distance of closest approach $r_0$. The location of the three peaks $Q_{\mathrm{I}}$, $Q_{\mathrm{II}}$, and $Q_{\mathrm{III}}$ varies with $r_0$, but their energy separations remain independent of $r_0$. For the heteronuclear collisions reported here, the values of the $Q$-peak separations suggest that $Q_{\mathrm{II}}$ and $Q_{\mathrm{III}}$ correspond to the production of one and two $L_{2,3}$ vacancies, respectively, in one of the colliding particles, viz., the one with the lower atomic number. This is further supported by studies of Auger electrons emitted in the collisions.