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Deep Minima in the Triply Differential Cross Section for Ionization of Atomic Hydrogen by Electron and Positron Impact

1
Department of Physics, University of North Texas, Denton, TX 76203, USA
2
Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
3
Department of Physics, Missouri University of Science and Technology, Rolla, MI 65409, USA
*
Author to whom correspondence should be addressed.
Atoms 2020, 8(2), 26; https://doi.org/10.3390/atoms8020026
Received: 6 May 2020 / Revised: 23 May 2020 / Accepted: 25 May 2020 / Published: 29 May 2020
We investigate ionization of atomic hydrogen by electron- and positron-impact. We apply the Coulomb–Born (CB1) approximation, various modified CB1 approximations, the three body distorted wave (3DW) approximation, and the time-dependent close-coupling (TDCC) method to electron-impact ionization of hydrogen. For electron-impact ionization of hydrogen for an incident energy of approximately 76.45 eV, we obtain a deep minimum in the CB1 triply differential cross section (TDCS). However, the TDCC for 74.45 eV and the 3DW for 74.46 eV gave a dip in the TDCS. For positron-hydrogen ionization (breakup) we apply the CB1 approximation and a modified CB1 approximation. We obtain a deep minimum in the TDCS and a zero in the CB1 transition matrix element for an incident energy of 100 eV with a gun angle of 56.13 ° . Corresponding to a zero in the CB1 transition matrix element, there is a vortex in the velocity field associated with this element. For both electron- and positron-impact ionization of hydrogen the velocity field rotates in the same direction, which is anticlockwise. All calculations are performed for a doubly symmetric geometry; the electron-impact ionization is in-plane and the positron-impact ionization is out-of-plane. View Full-Text
Keywords: electron-impact ionization; hydrogen; positron-impact ionization; velocity field; vortices electron-impact ionization; hydrogen; positron-impact ionization; velocity field; vortices
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DeMars, C.M.; Ward, S.J.; Colgan, J.; Amami, S.; Madison, D.H. Deep Minima in the Triply Differential Cross Section for Ionization of Atomic Hydrogen by Electron and Positron Impact. Atoms 2020, 8, 26.

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