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Title: Effects of the final-state electron-ion interactions on the fully differential cross sections for heavy-particle-impact ionization of helium

Abstract

Three-dimensional fully differential cross sections for heavy-particle-impact ionization of helium are examined. Previously, the three-body distorted-wave (3DW) model has achieved good agreement with experiment in the scattering plane for small momentum transfers, but poor agreement for large momentum transfers. Poor agreement was also observed outside the scattering plane for all momentum transfers. In particular, the 3DW calculations predicted cross sections that were too small both perpendicular to the scattering plane and for large momentum transfers. The important unanswered question concerns the physical effects that cause the significant disagreement between experiment and theory. In previous works, the role of the projectile-ion interaction has been examined. Although the importance of exchange between the ejected electron and the residual bound electrons has been well established, and frequently studied, for electron-impact ionization, the importance of this effect has not been examined for heavy-particle scattering. In this paper we examine the role of this effect for heavy-particle scattering.

Authors:
; ;  [1];  [2];  [3];  [4]
  1. University of Missouri-Rolla, Rolla, Missouri 65409 (United States)
  2. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  3. Drake University, Des Moines, Iowa 50311 (United States)
  4. University of Central Florida, Orlando, Florida 32816 (United States)
Publication Date:
OSTI Identifier:
20982338
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.75.032718; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOMS; DIFFERENTIAL CROSS SECTIONS; DISTORTED WAVE THEORY; ELECTRON-ION COLLISIONS; ELECTRON-ION COUPLING; ELECTRONS; HELIUM; INTERACTIONS; IONIZATION; IONS; MOMENTUM TRANSFER; SCATTERING; THREE-BODY PROBLEM; THREE-DIMENSIONAL CALCULATIONS

Citation Formats

Harris, A. L., Madison, D. H., Peacher, J. L., Foster, M., Bartschat, K., and Saha, H. P. Effects of the final-state electron-ion interactions on the fully differential cross sections for heavy-particle-impact ionization of helium. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.032718.
Harris, A. L., Madison, D. H., Peacher, J. L., Foster, M., Bartschat, K., & Saha, H. P. Effects of the final-state electron-ion interactions on the fully differential cross sections for heavy-particle-impact ionization of helium. United States. doi:10.1103/PHYSREVA.75.032718.
Harris, A. L., Madison, D. H., Peacher, J. L., Foster, M., Bartschat, K., and Saha, H. P. Thu . "Effects of the final-state electron-ion interactions on the fully differential cross sections for heavy-particle-impact ionization of helium". United States. doi:10.1103/PHYSREVA.75.032718.
@article{osti_20982338,
title = {Effects of the final-state electron-ion interactions on the fully differential cross sections for heavy-particle-impact ionization of helium},
author = {Harris, A. L. and Madison, D. H. and Peacher, J. L. and Foster, M. and Bartschat, K. and Saha, H. P.},
abstractNote = {Three-dimensional fully differential cross sections for heavy-particle-impact ionization of helium are examined. Previously, the three-body distorted-wave (3DW) model has achieved good agreement with experiment in the scattering plane for small momentum transfers, but poor agreement for large momentum transfers. Poor agreement was also observed outside the scattering plane for all momentum transfers. In particular, the 3DW calculations predicted cross sections that were too small both perpendicular to the scattering plane and for large momentum transfers. The important unanswered question concerns the physical effects that cause the significant disagreement between experiment and theory. In previous works, the role of the projectile-ion interaction has been examined. Although the importance of exchange between the ejected electron and the residual bound electrons has been well established, and frequently studied, for electron-impact ionization, the importance of this effect has not been examined for heavy-particle scattering. In this paper we examine the role of this effect for heavy-particle scattering.},
doi = {10.1103/PHYSREVA.75.032718},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • We have carried out calculations for the fully differential cross section of the ionization of helium by electron projectiles. In order to study the effect of the residual ion potential, we employed three models, and tested them for the coplanar and perpendicular plane geometry. In spite of the simplicity of our models, the results for the coplanar case are in fair agreement with the available experimental data. The results for the perpendicular geometry need more improvement.
  • We have calculated the probability for double ionization of helium by fast heavy-ion impact in the equivalent-photon picture. We find that the {ital shape} of differential cross sections is significantly affected by the inclusion of the electron-electron interaction in both the initial and the final channel, but is rather insensitive to the projectile charge and impact velocity. {copyright} {ital 1997} {ital The American Physical Society}
  • Currently there is no accurate theoretical approach available for treating fully differential cross sections (FDCS) for low-energy electron-impact ionization of large molecules. For high incident energies, the plane wave impulse approximation (PWIA) generally yields good agreement with experimental data. In this paper, the distorted wave impulse approximation (DWIA) is used to calculate FDCS for low-energy electron-impact ionization of N{sub 2}. To perform the necessary average over all molecular orientations, we propose an orientation average (OA) approximation. Although the DWIA results represent an improvement over the PWIA for intermediate energies, an improved theory is necessary for lower energies. However, the OAmore » approximation will greatly simplify the evaluation of improved theories for lower energies.« less
  • An approach to the calculation of the impulsive (e,2e) cross section, which extends the plane-wave-impulse approximation to include the long-range tails of the Coulomb interaction in the final state, is presented. The model divides the collision space into two regions: an inner sphere where short-range forces are active and responsible for the impulsive character of the collision, and an outer region where the tails of the Coulomb interactions act on the charged free particles, which can be treated in a semiclassical way. An extensive comparison between the predictions of this model and experimental data relative to atomic hydrogen and helium,more » as derived from the literature, is presented. The model constitutes an improvement over previous impulsive models, mainly for the angular distributions of (e,2e) events.« less
  • Double, single, and total ionization cross sections have been calculated for the single ionization process of an electron-helium atom system for the incident energy range (50{endash}300 eV) including the electron exchange effect. The final-state wave function involves a correlated three-body Coulomb continuum, and satisfies the three-body asymptotic boundary condition. The electron exchange effect is found to play a dominant role for near-symmetric and symmetric geometries. All results have been compared with available experiments, and reasonably good agreement has been noted except for low incident energies (e.g., 50 eV) and low ejected energies (in the double-differential or single-differential cross-section level). {copyright}more » {ital 1996 The American Physical Society.}« less