Differential cross sections for K-shell ionisation and capture by H+in C (CH4) and Ne

Abstract
Cross sections differential in projectile scattering angle for total K-shell-vacancy production and for electron capture from the K shell by 200-600 keV H+ in carbon (CH4) and 500-1500 keV H+ in neon have been measured using scattered-particle, Auger electron coincidence techniques. The collision velocities range from 0.46 to 0.86 in units of the K-shell velocities, and the scattering angles correspond to impact parameters within a region around the K-shell radius. The ratio between the differential cross sections for K-shell capture and for total K-shell-vacancy production depends weakly on the scattering angle at the present collision velocities. The measured differential cross sections are transformed to impact parameter dependent probabilities to facilitate comparison with theoretical predictions. First-order perturbation theory with accurate initial and final electronic wavefunctions reproduces the main characteristics of the experimental ionisation probabilities. Recent progress in the theoretical description of capture in asymmetric collisions brings the theoretical predictions into close agreement with the experimental data for the capture process.

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