Electron impact multiple ionization of argon ions

Belic, D. S. Lecointre, Julien [UCL] Defrance, Pierre [UCL]

Absolute cross sections for electron impact single and multiple ionization of argon ions leading to the formation of Arq+ (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 Arq+ (q = 2-8) are measured to be (12.6 +/- 0.6) x 10(-17) cm(2) for Ar2+, (4.96 +/- 0.21) x 10(-18) cm(2) for Ar3+, (5.50 +/- 0.23) x 10(-19) cm(2) for Ar4+, (8.10 +/- 0.33) x 10(-20) cm(2) for Ar5+, (8.2 +/- 0.7) x 10(-21) cm(2) for Ar6+, (8.9 +/- 0.8) x 10(-22) cm(2) for Ar7+ and (5.5 +/- 1.6) x 10(-23) cm(2) 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 Arq+ (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.