Double−K−vacancystates in electron-impact single ionization of metastable two-electronN5+(1s2s

Abstract

The role of hollow states intermediately produced in electron-impact ionization of metastable He-like N 5+ (1s2s 3 S 1) ions has been investigated in detail. A crossed-beam setup and suitable experimental techniques were employed for the measurement of accurate absolute cross sections and precise energy-scan data. Fine structures arising from K-shell excitations and associated resonances have been observed for this two-electron ion with less than ±0.5 eV uncertainty on the energy scale. Fine details, such as interference of the reaction pathways of direct ionization and excitation with capture of the incident electron followed by double-Auger decay, could be revealed. Ab initio calculations based on the convergent close coupling (CCC) approach are in good agreement with the experiment.

Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

“…Fine energy scans with very good statistics at small energy steps reveal ionization thresholds of different beam components [107]. Theoretical modeling of the resulting apparent cross sections which are typically measured with uncertainties of less than 10% provides information about the fractions of beam components and hence reliable cross sections for the ground state of the investigated ion, which is usually the dominant beam component.…”

“…Expectations for the theoretical description of ionization cross sections for ions imply that the distorted-wave calculations become increasingly better with increasing charge state of the parent ion while resonances [17,107,108] are of decreasing significance. In the experiments studying electron-impact ionization of tungsten ions, no significant contributions of resonant processes could be found in the range of charge states q from 1 to 19 at energies up to 1 keV.…”

Electron–ion merged-beam experiments at heavy-ion storage rings

“…These differences are mainly related to the neglect of resonant ionization processes in the calculation (for a detailed discussion see Bernhardt et al 2014). For a comprehensive theoretical understanding of EII of atomic ions, resonant processes as well as interference effects have to be included in a unified approach (see, e.g., Müller et al 2014) that goes beyond the widely used independent-processes approximation. As compared to the single-pass crossed-beams technique (see, e.g., Müller et al 2014) the storage-ring mergedbeam technique offers additional control of the ion beam composition.…”

“…For a comprehensive theoretical understanding of EII of atomic ions, resonant processes as well as interference effects have to be included in a unified approach (see, e.g., Müller et al 2014) that goes beyond the widely used independent-processes approximation. As compared to the single-pass crossed-beams technique (see, e.g., Müller et al 2014) the storage-ring mergedbeam technique offers additional control of the ion beam composition. In a storage-ring, metastable components that often contaminate the ion beam in single-pass experiments can relax to the ground state before data taking starts.…”

Photoionization of metastable heliumlike C4+(1s2sS13Müller1, Lindroth2, Bari3 et al. 2018Phys. Rev. ASelf Cite410420View full textAdd to dashboardCite

“…In recent electron-ion collision experiments with heliumlike ions, doubly excited states were produced starting from the 1s2s 3 S 1 levels of Li + [32] and N 5+ ions [33]. With the parent ion already containing a K-shell vacancy, excitation of a single electron can produce a doubly excited state with a relatively large cross section.…”