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Recently, we have demonstrated (Jin et al 2020 J. Phys. B: At. Mol. Opt. Phys. 53 075201) that a hybrid subconfiguration-average and level-to-level distorted wave treatment of electron-impact single ionisation (EISI) of W14+ ions represents an accurate and manageable approach for the calculation of EISI cross sections of a complex ion. Here we demonstrate the more general validity of this approach by comparing hybrid cross sections for EISI of W15+ and W16+ with the recent experimental results of Schury et al (2020 J. Phys. B: At. Mol. Opt. Phys. 53 015201). Our calculations also account for the resonant-excitation double autoionisation (REDA) process which is important in the electron energy range 370–600 eV and for the possible presence of initially metastable ions in the experiment. [ABSTRACT FROM AUTHOR]

Recently, we have demonstrated (Jin et al 2020 J. Phys. B: At. Mol. Opt. Phys. 53 075201) that a hybrid subconfiguration-average and level-to-level distorted wave treatment of electron-impact single ionisation (EISI) of W14+ ions represents an accurate and manageable approach for the calculation of EISI cross sections of a complex ion. Here we demonstrate the more general validity of this approach by comparing hybrid cross sections for EISI of W15+ and W16+ with the recent experimental results of Schury et al (2020 J. Phys. B: At. Mol. Opt. Phys. 53 015201). Our calculations also account for the resonant-excitation double autoionisation (REDA) process which is important in the electron energy range 370–600 eV and for the possible presence of initially metastable ions in the experiment. [ABSTRACT FROM AUTHOR]

Absolute cross sections for electron-impact single ionisation (EISI) of multiply charged tungsten ions (Wq+) with charge states in the range in the electron–ion collision energy ranges from below the respective ionisation thresholds up to 1000 eV were measured employing the electron–ion crossed-beams method. In order to extend the results to higher energies, cross section calculations were performed using the subconfiguration-averaged distorted-wave (SCADW) method for electron–ion collision energies up to 150 keV. From the combined experimental and scaled theoretical cross sections rate coefficients were derived which are compared with the ones contained in the ADAS database and that are based on previous configuration-averaged distorted wave (CADW) calculations of Loch et al (2005 Phys. Rev. A 72 052716). Significant discrepancies were found at the temperatures where the ions investigated here are expected to form in collisionally ionised plasmas. These discrepancies are attributed to the limitations of the CADW approach and also the more detailed SCADW treatment which do not allow for a sufficiently accurate description of the EISI cross sections particularly at the ionisation thresholds. [ABSTRACT FROM AUTHOR]

Absolute and energy scanned cross sections for the electron-impact single ionization of Xeq + (q = 10–17) atomic ions are measured by employing a crossed-beams technique in the collision energy range from threshold to 1000 eV. Direct ionization and indirect excitation-autoionization cross sections are calculated using a configuration-average distorted-wave method for the ground and first same parity excited configuration of the Xeq + (q = 10–17) atomic ions. Both the crossed-beams experiment and distorted-wave theory show a steady decrease in the ionization cross section as the charge of the ion increases. The disagreements between experiment and theory are partly attributed to the many metastable levels of ground and excited configurations found in the ion beam. [ABSTRACT FROM AUTHOR]

The photon-ion merged-beams technique has been employed at the new Photon-Ion spectrometer at PETRA III for measuring multiple photoionization of Xeq + (q = 1–5) ions. Total ionization cross sections have been obtained on an absolute scale for the dominant ionization reactions of the type hν + Xeq + → Xer + + (q − r)e− with product charge states q + 2 ⩽ r ⩽ q + 5. Prominent ionization features are observed in the photon-energy range 650–750 eV, which are associated with excitation or ionization of an inner-shell 3d electron. Single-configuration Dirac–Fock calculations agree quantitatively with the experimental cross sections for non-resonant photoabsorption, but fail to reproduce all details of the measured ionization resonance structures. [ABSTRACT FROM AUTHOR]