Electron-impact ionization of Pb{sup q+} ions for q=1-10
- 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, Vol. 72, Issue 3; Other Information: DOI: 10.1103/PhysRevA.72.032713; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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