Calculations of electron-impact single-ionization cross sections of helium isoelectronic systems

Abstract

The electron-impact single-ionization cross sections on the helium isoelectronic targets He, Li + , B 3+ , C 4+ , N 5+ , O 5+ , Ne 8+ , Na 9+ , Fe 24+ , Ag 45+ , and U 90+ , are calculated using the recent simplified version of the binary-encounter dipole (siBED) model as applied by Huo [Phys. Rev. A 64, 042719 (2001)] to various molecular targets. The simple siBED model is good for the helium atom, but it is inadequate for ionic targets. Our proposed modifications: (i) ionic correction of the siBED model (QIBED) and (ii) relativistic corrections of the siBED model (RQIBED) are examined on a wider group of species and compared with other available experimental and theoretical results. The predictions of QIBED in the nonrelativistic energy domain and of RQIBED for all energies, with the same parameter values of siBED, produce excellent agreement with the experimental data and the results close to those of other theories for all the two-electron systems, neutral or ions on the same footing.

Calculations for electron impact ionization of Be atoms and its charged states, Be+and Be2+

“…RMPS calculations [8,21] have also been done for the electron impact excitation processes on Be 3+ ions. Detailed study of electron impact ionization cross sections have been reported for the Be isoelectronic ions using various theoretical approaches such as two potential distorted wave approximation [22], simplified improved binary-encounter dipole model (siBED) [23,24], QIBED (with the ionic correction) and RQIBED (with both the ionic and relativistic corrections) [25]. Electron impact cross sections for beryllium and beryllium hydrides have also been reported recently [26].…”

Measurements of Lα, Lβx-ray production cross sections of Pb by 16–40 keV electron impact

“…Recently, Kim et al extended the binary-encounter-dipole model to the relativistic energy region of the incident electron and calculated the K-shell ionization cross sections by electron impact [7,8]; this model was also applied most recently to calculate the L-shell x-ray production cross sections by electron impact [9]. Uddin et al employed the modified version of the improved binary-encounter-dipole model, into which the ionic and relativistic effects have been incorporated, to calculate the K-shell ionization cross sections by electron impact in a wide range of atomic number from Z = 6 to 50 and in the energy region up to about 10 MeV [10,11]. Colgan et al [3] and Segui et al [2] recently developed relativistic distorted-wave Born approximation theories (DWBA) to calculate K, L-shell ionization cross sections by electron/positron impact.…”

Empirical Model for the Ionization Cross Sections of H- and He-Like Ions

“…Crandall et al [5], Donets and Ovsyannikov [6], Rachafi et al [7], Duponchelle et al [8], and Marrs et al [9,10]; and the results from the parent HEMP model [2], the RQIBED model of Uddin et al [11] and available calculations from quantal methods. The latter includes the fit formula to the distorted wave Born approximation (DWBA) calculations of Younger [12], the analytic fit formula of Fontes et al [13] coined here as FRDWBA, emerging from the relativistic DWBA theory including the Breit interaction [14], and the relativistic DWBA theory with the inclusion of the Mller interaction [15] plus exchange (RDWBA) of Moores and Reed [16].…”