Near-Threshold Cross Sections for Electron and Positron Impact Ionization of Atomic Hydrogen

I. Bray, A. W. Bray, D. V. Fursa, and A. S. Kadyrov
Phys. Rev. Lett. 121, 203401 – Published 16 November 2018

Abstract

Using classical arguments Wannier [Phys. Rev. 90, 817 (1953)] proposed an electron-impact ionization cross section for neutral atoms to behave as E1.127, where E is the excess energy above threshold. Using similar arguments Klar [J. Phys. B 14, 4165 (1981)] obtained E2.65 to be the corresponding threshold law for positron impact. Recently, Babij et al. [Phys. Rev. Lett. 120, 113401 (2018)] measured near-threshold positron-impact breakup behavior to be similar to that expected for electrons. Using the convergent close-coupling method for the atomic hydrogen target, we examine cross sections at near-threshold energies for electron and positron impact. Contrary to the experiment, the calculated cross sections are found to behave differently for the two projectiles and consistently with the aforementioned threshold laws, despite the entirely quantum nature of these problems. For electron impact, the threshold behavior holds while the total electron spin asymmetry remains constant, whereas for positron scattering the threshold law holds for breakup while the positronium-formation component of the ionization cross section remains constant.

  • Figure
  • Figure
  • Received 11 September 2018

DOI:https://doi.org/10.1103/PhysRevLett.121.203401

© 2018 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

I. Bray1, A. W. Bray2, D. V. Fursa1, and A. S. Kadyrov1

  • 1Curtin Institute for Computation and Department of Physics and Astronomy, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
  • 2Research School of Physics and Engineering, The Australian National University, Canberra, Australian Capital Territory 0200, Australia

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Issue

Vol. 121, Iss. 20 — 16 November 2018

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