Electron-impact single ionisation of W 14+ ions: subconfiguration-average and level-to-level distorted wave calculations

The cross section for electron-impact single ionisation of W14+ ions has been calculated by using two different approaches, i.e. the subconfiguration averaged distorted-wave (SCADW) method and the more involved level-to-level distorted-wave (LLDW) method. Both methods are found to yield very similar results except for the 4d. 5d excitation-autoionisation (EA) channels that straddles the ionisation threshold. Accordingly, a hybrid theoretical cross section where the 4d. 5d EA SCADW cross section is replaced by its LLDW counterpart is in good agreement with the experimental result from an electron-ion crossed-beams experiment. This is in contrast to pure SCADW calculations for W14+ and neighbouring charge states which exhibit significant deviations from the experimental near-threshold cross sections of Schury et al (2020 J. Phys. B: At. Mol. Opt. Phys. 53 015201).