Electron-impact ionization of Pb{sup q+} ions for q=1-10

Journal Article · Thu Sep 15 04:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.032713· OSTI ID:20718551

Loch, S D; Ludlow, J A; Pindzola, M S; Scheuermann, F; Kramer, K; Fabian, B; Huber, K; Salzborn, E ^[1]

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1. Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)

Theoretical calculations and experimental crossed-beam measurements are compared for electron-impact single ionization of Pb{sup q+} ions for q=1-10. We compare with two main theoretical methods. First, we check against configuration-average distorted-wave calculations, which include both direct-ionization and indirect excitation-autoionization contributions. Second, for ion stages Pb{sup +} through to Pb{sup 5+}, we calculate the dominant excitation-autoionization channels using level-resolved distorted-wave theory to evaluate the excitation cross sections. We find that for ion stages Pb{sup +}, Pb{sup 2+}, and Pb{sup 3+}, distorted-wave theory significantly overestimates the total-ionization cross section, due to an overestimation of the direct-ionization cross section from the 5d subshell. For ion stages Pb{sup 4+} through to Pb{sup 10+} there is good agreement between theory and experiment. We find evidence for significant metastable fraction in the ion beam of the experiment for ion stages Pb{sup 2+}, Pb{sup 3+}, Pb{sup 4+}, Pb{sup 5+}, and Pb{sup 6+}. For ion stage Pb{sup 3+} we find that the level-resolved distorted-wave calculation of the excitation autoionization results in a slight reduction of the configuration-average theoretical results, due to splitting of levels within the autoionizing configurations. We also investigate two semiempirical methods of calculating the direct-ionization cross sections: namely, the Lotz method and the binary encounter Bethe method. We find that both methods provide results which are significantly lower than the distorted-wave method for the 5d-subshell direct ionization of Pb{sup +}, Pb{sup 2+}, and Pb{sup 3+}. For the higher ion stages, both methods are lower than the distorted-wave direct-ionization cross-section results, trending towards the distorted-wave results as the ion stage increases.

• OSTI ID: 20718551
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 3 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
AUTOIONIZATION
CATIONS
COLLIDING BEAMS
COMPARATIVE EVALUATIONS
DISTORTED WAVE THEORY
ELECTRON-ATOM COLLISIONS
ELECTRONS
EXCITATION
ION BEAMS
LEAD IONS
METASTABLE STATES
MULTICHARGED IONS