The present single-ionization cross section of Sn<sup>4 +</sup> (open circles, absolute cross-section data; grey thin solid line, energy scan) compared to the results of the present CADW calculations

<p><strong>Figure 2.</strong> The present single-ionization cross section of Sn<sup>4 +</sup> (open circles, absolute cross-section data; grey thin solid line, energy scan) compared to the results of the present CADW calculations. The individually shaded areas show contributions of processes involving the indicated subshells. DI and EA denote direct ionization and excitation-autoionization processes, respectively. The thick dashed line separates total contributions of direct (lower area) and indirect (upper area) ionization processes arising from the ground state. The dark shaded area at the bottom of the graph represents the total ionization contribution of the excited-ion-beam fraction with configuration 4d<sup>9</sup>5s. This fraction is estimated to be 55% of the present ion beam. The vertical arrow indicates the ground-state ionization potential.</p> <p><strong>Abstract</strong></p> <p>Electron-impact single-ionization cross sections of Sn<sup><em>q</em> +</sup> ions in charge states <em>q</em> = 4–13 with 4d<sup>[10 − (<em>q</em> − 4)]</sup> outer-shell configurations have been studied in the energy range from the corresponding thresholds up to 1000 eV. Absolute cross sections and fine-step energy-scan data have been measured employing the crossed-beams technique. Contributions of different ionization mechanisms have been analysed by comparing the experimental data with calculations employing the configuration-averaged distorted wave approximation. Ionization plasma rate coefficients inferred from the experimental data are also presented.</p>