Electron-impact multiple ionization of Baq+ ions (1⩽q⩽13) via resonant 3d excitation

Abstract

One ionization mechanism of barium ions is the resonant excitation of a 3d inner-shell electron with the subsequent decay of the resulting highly excited intermediate state by multiple autoionization processes. We have experimentally studied this process by observing associated resonance structures – in the energy range 700–800 eV – in the multiple (up to sevenfold) ionization cross-sections of Baq+ ions with 1⩽q⩽13. The 3d-resonance strength is determined quantitatively as a function of initial and final ion charge state. The results suggest a statistical description of multiple ionization via the excitation of inner-shell electrons.