Absolute cross section measurements for electron impact ionization of Ar⁷⁺

Abstract

The first absolute cross section measurements for single and double electron impact ionization of sodium-like A?* are reponed. The animated crossed beams method has been employed in the energy range from threshold to 3000eV. The measured cross sections for single ionization are higher than the theoretical and semi-empirical predictions by about 20-50%. This discrepancy has been associated with the contribution o f the indirect ionization processes. The double ionization cross section is only 1% of the single one.

Ionization rate coefficients for the elements hydrogen through zinc

“…In this area, their calculations agree with the measurements of Zhang et al (1992). At energies above 700 eV, the FAC, Tayal (1994), Reed & Chen (1996) and Teng & Xu (1996) cross sections are in good agreement with the measurements of Rachafi et al (1991) and the cross sections of Griffin et al appear to approach these measurements as well.…”

“…The measurements are well described by the FAC DI cross sections plus the EA cross sections multiplied by a factor of 0.65. The measured cross sections of Ar viii by Rachafi et al (1991) and Zhang et al (1992) do not agree very well. At low energies, the error bars are quite large.…”

X-ray emission from thin plasmas

“…We decided not to include the measurements for Ar viii (Rachafi et al 1991;Zhang et al 2002) and Cr xiv (Gregory et al 1990), because they are higher and lower, respectively, compared with the other elements on this sequence. The Ar viii measurements are probably affected by the presence of resonant excitation double Auger ionization (REDA).…”

Electron-impact Multiple-ionization Cross Sections for Atoms and Ions of Helium through Zinc

“…Double ionization measurements exist for Al 2+ (Steidl et al 1999) and for Ar 7+ (Tinschert et al 1989;Rachafi et al 1991;Zhang et al 2002). The Ar 7+ measurements are illustrated in Figure 10.…”