Electron-impact ionization of W5+

Electron-impact single-ionization cross sections for the W5+ ion have been studied experimentally and theoretically. Measurements of a detailed ionization spectrum and of absolute cross sections were performed employing the crossed-beams method in the energy range from the ionization onset up to 1000 eV. The experimental data show a prominent contribution of W5+ ions in metastable states. The theoretical analysis includes level-to-level calculations from the 4f145s25p65d ground configuration and long-lived levels of the 6s, 5p55d2, 4f135d2, and 4f135d6s configurations. Direct-ionization and excitation-autoionization contributions to the total single-ionization cross sections were calculated employing a distorted-wave approximation. Radiative damping was taken into account. It is shown that correlation effects play an important role and lead to substantial reduction of cross sections. Theory and experiment are in quite good agreement when, within a statistical model, a (85±9)% fraction of parent ions in the ground configuration is assumed. The strongest contributions of metastable parent ions arise from the 5p55d2 and 4f135d2 configurations.The experimental part of this study was supported by the Deutsche Forschungsgemeinschaft under Project No. Mu 1068/20. M.F.G. acknowledges the Deutsche Forschungsgemeinschaft for supporting his research stays at the Gießen Institut für Atom-und Molekülphysik through Grants No. Mu-1068/19 and No. Mu-1068/21. A.B. is supported by the German Federal Ministry of Education and Research (BMBF) through Grant No. 05P19RGFA1. Part of the computations were performed using resources of the High Performance Computing Center “HPC Sauletekis” in Vilnius University Faculty of Physics. We thank K. Spruck, A. Becker, J. Hellhund, and J. Rausch for their help in the present experimental program.Scopu