Electron impact multiple ionization of argon ions

Absolute cross sections for electron impact single and multiple ionization of argon ions leading to the formation of Ar q + ( q = 2–8) are reported. The animated crossed beam method is applied in the energy range extending from the respective thresholds up to 2.5 keV. The maximum cross sections for the multiply charged products Ar q + ( q = 2–8) are measured to be (12.6 ± 0.6) × 10 −17 cm 2 for Ar 2+ , (4.96 ± 0.21) × 10 −18 cm 2 for Ar 3+ , (5.50 ± 0.23) × 10 −19 cm 2 for Ar 4+ , (8.10 ± 0.33) × 10 −20 cm 2 for Ar 5+ , (8.2 ± 0.7) × 10 −21 cm 2 for Ar 6+ , (8.9 ± 0.8) × 10 −22 cm 2 for Ar 7+ and (5.5 ± 1.6) × 10 −23 cm 2 for Ar 8+ . The corresponding threshold energies are determined to be (27.4 ± 0.5) eV, (68.7 ± 0.5) eV, (135 ± 2) eV, (250 ± 10) eV, (310 ± 10) eV, (480 ± 20) eV and (640 ± 40) eV for the production of Ar q + ( q = 2–8), respectively. The direct process is seen to dominate for q = 2–3, while the indirect processes are dominant for charge states 4–8.