Electron-impact ionization of neon ions (q = 4-8)

Absolute cross section measurements for electron-impact single ionization of Neq+ (q = 4-8) ion and for double ionization of Ne5+ and Ne6+ are reported. The animated crossed-beams method has been applied. The measurements cover the energy range from threshold to several keV. The Ne4+ and Ne6+ ion beams are found to contain an important population of ions formed in metastable states. For single ionization, results are in overall good agreement with direct ionization theoretical predictions, when available. Excitation-autoionization is observed in the ionization threshold region for Ne4+ and in the K-L transition energy region for Ne6+ and Ne7+. Double ionization of Ne5+ and Ne6+ is found to be dominated by K-shell ionization followed by autoionization. (author)