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  Semiempirical formulae for electron-impact double-ionization cross sections of light positive ions

Shevelko, V. P., Tawara, H., Scheuermann, F., Fabian, B., Müller, A., & Salzborn, E. (2005). Semiempirical formulae for electron-impact double-ionization cross sections of light positive ions. Journal of Physics B: Atomic, Molecular and Optical Physics, 38(5), 525-546. doi:doi:10.1088/0953-4075/38/5/006.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0011-894D-8 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0011-894E-6
Genre: Journal Article

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 Creators:
Shevelko, V. P.1, Author              
Tawara, H.1, Author              
Scheuermann, F.2, Author
Fabian, B.2, Author
Müller, A.2, Author
Salzborn, E.2, Author
Affiliations:
1Division Prof. Dr. Joachim H. Ullrich, MPI for Nuclear Physics, Max Planck Society, ou_904547              
2P N Lebedev Physical Institute, 119991 Moscow, Russia Department of Physics, The Queen's University, Belfast BT7 1NN, UK Institute for Atomic and Molecular Physics, D-35392 Giessen, Germany, ou_persistent22              

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 Abstract: Electron-impact double-ionization processes of light positive ions from He- to Ne-like isoelectronic sequences, as well as of the heavy ions Arq+ (q = 1–7) and Kr q+ (q = 1–4) are considered for incident-electron energies E < 50 Ith where Ith is the threshold energy for double-electron ionization. On the basis of reliable experimental data and quantum-mechanical calculations, simple semiempirical formulae with three fitting parameters, by taking into account the contribution of direct double ionization and of inner-shell ionization processes, are obtained which describe the experimental cross sections within an accuracy of 20–30%. With this accuracy, the formulae suggested can be used for prediction of the double-ionization cross sections of positive ions with the nuclear charge Z ≤ 26 in the electron energy range of E < 50Ith. According to the model suggested, the direct ionization cross section σdir (simultaneous ionization of two outer electrons) is scaled as I-3th against scaled electron energy E/Ith and contains only one fitting parameter. Two additional fitting parameters are obtained using the least-squares method in conjunction with numerically calculated single-electron inner-shell ionization cross sections. All fitting parameters are found to be constant for ions within a given isoelectronic sequence. The present analysis also provides a method for indirect determination of K-shell ionization cross sections for ions from Be-like to Ne-like sequences. The fluorescence yields ωK for a single K-shell vacancy in ions from Li-like to Ne-like sequences with nuclear charges 3 ≤ Z ≤ 26 are calculated as well.

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 Dates: 2005-03-14
 Publication Status: Published in print
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 Rev. Method: Peer
 Identifiers: eDoc: 280896
DOI: doi:10.1088/0953-4075/38/5/006
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Title: Journal of Physics B: Atomic, Molecular and Optical Physics
  Alternative Title : J. Phys. B: At. Mol. Opt. Phys.
Source Genre: Journal
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Pages: - Volume / Issue: 38 (5) Sequence Number: - Start / End Page: 525 - 546 Identifier: -