Electron-impact single- and multiple ionization cross sections of xenon and tin ions have been experimentally studied.An animated crossed-beams method has been applied with the angle of 90 degrees between the beams. The ion beam was extracted from a 10 GHz Electron-Cyclotron-Resonance (ECR) ion source and mass-over-charge analyzed using a dipole magnet. The electron beam was produced using a high-current electron gun. Space-charge limited electron currents were up to 450 mA at 1000 eV. Ion currents ranged from 0.1 to 200 nA. The reaction products were separated from the primary ion beam by another dipole magnet and registered by a single particle detector, whereas the primary ion beam was collected by a moveable Faraday cup.Ionization cross sections have been measured for the energy regions from threshold up to 1000 eV. For Xeq+ ions single-ionization cross sections have been measured for all charge states q = 1, 2, 3, ..., 25, double-ionization for q = 1, 2, 3, ..., 17. Triple- and fourfold-ionization cross-sections have been obtained for charge states q = 1, 6, 7. For Xe+ cross sections for all final charge states q´ = 3, 4, ..., 10 have been measured for multiple ionization processes q -> q´. For Snq+ ions single-ionization cross sections for charge states 1 through 13 and double-ionization cross sections for charge states 1 through 12 have been obtained. The magnitude of the smallest measured cross section was of the order of 10-24 cm2 with error bars of about 10-25 cm2. This is one order of magnitude smaller than the smallest ionization cross section ever measured using interacting beam techniques.The obtained data reveal an important, sometimes dominant role of inner electron subshell ionization or excitation of ions giving rise to indirect ionization mechanisms, which can cause strong contributions to ionization cross sections.In addition, in primary-ion beams fractions of ions in metastable states have been found. Excitation energies for some of them reach up to 850 eV and lifetimes were found to range at least from few to several tens of microseconds.
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