State-selective K-K electron transfer and K ionization cross sections for Ar and Kr in collisions with highly charged C, O, F, S, and Cl ions at intermediate velocities

We have measured the single K-K electron-transfer cross sections along with the single K-shell ionization cross sections of Ar induced by H-like and bare C,O, and F projectiles, and of Kr by F, S, and Cl ions in the energy range 1.5–6 MeV u^-1. The target x-ray yields as a function of the number of K shell vacancies in the incident beam were used to derive the K ionization cross sections of the targets and the K-K (i.e., target K shell to projectile K shell) electron-transfer cross sections. The enhancement in the fluorescence yield due to multiple vacancies in the target atom was deduced from the energy shifts and intensity ratios of the characteristic x-ray lines to derive vacancy production cross sections from the measured x-ray production cross sections. The energy shifts of K x-ray lines were found to be dependent on the incident charge states of the projectiles. Continuum-distorted-wave eikonal-initial-state calculations are found to underestimate the ionization cross-section data in general, and the deviations are most pronounced for Kr. Perturbed stationary-state calculations, including corrective terms due to energy loss, Coulomb deflection, and relativistic wave function, agree with the data only for asymmetric collisions (Z₁/Z₂<~0.4), and largely overestimate for relatively symmetric systems. The K-K electron-transfer cross sections are well reproduced by the two-center close-coupling calculations for both targets except, for the asymmetric collisions. The perturbed stationary state (PSS) calculations of Lapicki and McDaniel are also used to explain the K-K electron-transfer data for the asymmetric systems. In addition, the K-L electron-transfer cross sections are also measured for S and Cl ions on Kr, and compared with the PSS calculations.