Electron impact multiple ionization of argon ions

Abstract

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 cm2 for Ar2+, (4.96 ± 0.21) × 10−18 cm2 for Ar3+, (5.50 ± 0.23) × 10−19 cm2 for Ar4+, (8.10 ± 0.33) × 10−20 cm2 for Ar5+, (8.2 ± 0.7) × 10−21 cm2 for Ar6+, (8.9 ± 0.8) × 10−22 cm2 for Ar7+ and (5.5 ± 1.6) × 10−23 cm2 for Ar8+. 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.