Production of multiply charged rare-gas ions by relativistic electrons

Abstract

Charge state spectra of ions generated in single collisions of 20 to 50 MeV electrons with rare-gas atoms have been measured by a time-of-flight technique. Relative abundances of ions in charge states up to 2+ for He, 3+ for Ne, 5+ for Ar, 7+ for Kr and 8+ for Xe were deduced from the experiment. Higher charge states, e.g. 12+ for Xe, could also be observed; however their quantitative fractions could not be determined. The relative abundances F_i of the different ion charge states i are constant in the investigated energy range; however they rapidly decrease with increasing i-strongly dependent on the atomic number of the bombarded target. The experimental results are in good agreement with calculations based on inner-shell ionisation cross sections folded with charge state distributions which result from the decay of the corresponding initial vacancies. The capability of fast electrons for efficient production of slow highly charged ions in single collisions with atoms is discussed.