An Explanation of the Structure Observed in Out-Of-Plane Symmetric Measurements on Helium

  • J. Rasch
  • Colm T. Whelan
  • R. J. Allan
  • H. R. J. Walters
Part of the Physics of Atoms and Molecules book series (PAMO)


The study of (e,2e) processes on Helium at impact energies of 100eV and below has yielded a wealth of experimental data and has contributed greatly to the understanding of the Coulomb few body problem. The great advantage of coincidence measurements is that one can manipulate the geometry of the experiment to study delicate processes which yield striking structures in a particular arrangement, but are largely masked by stronger effects in virtually all other setups. Quite recently Murray1 identified a very strong structure in the ionization of Helium at an impact energy of 64.6eV in a very specific out of plane geometry. In this paper we will show that this structure is well represented in a Distorted Wave Born Approximation (DWBA) calculation and we will interpret it as an interference, that is to say a pure quantum, effect. We predict that similar structures will be present in the Triple Differential Cross Section (TDCS) for some targets but not for others.


Impact Energy Distorted Wave Interference Structure Final Channel Distort Wave Born Approximation 
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  1. 1.
    A. J. Murray, Coupling the coplanar (e, 2e) to the perpendicular plane geometry, in: (c,2e) and Related Processes, Colin T. Whelan, H. R.. 1. Walters, A. Lahmam-Bennani. and H. Ehrhardt, eds., Kluwer Academic Publisher, (1993).Google Scholar
  2. 2.
    A. J. Murray, M. B. J. Woolf, and F. H. Read. Results from symmetric and non-symmetric energy sharing (e,2e) experiments in the perpendicular plane. J. Phys. B, 25: 3021. (1992).ADSCrossRefGoogle Scholar
  3. 3.
    Colm T. Whelan, R. J. Allan, H. R. J. Walters, and X. Zhang, (e,2e), effective charges, distorted waves and all that!, in: (e,2e) and Related Processes, Colm T. Whelan. H. R. J. Walters, A. Lahmam-Bennani. and H. Ehrhardt, eds., Kluwer Academic Publisher, (1993).Google Scholar
  4. 4.
    Clementi and Roetti, Roothan-hartree-rock atomic wavelunctions. Atomic Data and Nuclear - Data Tables, 14: 177, (1974).ADSCrossRefGoogle Scholar
  5. 5.
    J.B. Furness and 1.E McCarthy, Semiphenomenological optical model for electron scattering on atoms. J. Phys. B,6:2280, (1973)_Google Scholar
  6. 6.
    X. Zhang, Colin T. Whelan, and H. R. J. Walters, (c,2e) cross sections for ionization of helium in coplanar symmetric geometry. J. Phys. B, 23: L509, (1990).ADSCrossRefGoogle Scholar
  7. 7.
    L. Frost, P. Freinstein, and M. Wagner. 200cV coplanar symmetric (e,2e) on helium: a sensitive test of reaction models. J. Phys. B, 23: 1. 715, (1990).ADSCrossRefGoogle Scholar
  8. 8.
    T. R6se1, C. Dupré, J. Ruder, A. Duguet, K. Jung, A. Lahmam-Bennani, and H. Ehrhardt. Coplanar symmetric (e,2e) cross sections on helium and neon. J. Phys. B. 23: 3059, (1991).Google Scholar
  9. 9.
    Colm T. Whelan, X. Zhang, and H. R. J. Walters. in: Proceedings . of the European (bn/erenee on (e,2e) and related processe.v, G. Stelani, ed., CNR Rome, (1990).Google Scholar
  10. 10.
    J. Rasch, Cohn T. Whelan, and H. R. J. Walters.. in preparation, (1996). Google Scholar
  11. 11.
    H. R. J. Walters, X. Zhang, and Colm T. Whelan. Directions in (e,2e) and related processes, in: (e,2e) and Related Processes, Colm T. Whelan, H. R. J. Walters, A. Lahmam-Bennani. and H. Ehrhardt. eds., Kluwer Academic Publisher, (1993).Google Scholar
  12. 12.
    Colm T. Whelan, R. J. Allan, J. Rasch, H. R. J. Walters, X. Zhang, J. Ruder, K. Jung, and H. Ehrhardt, Coulomb three-body effects in (e,2e) collisions: The ionization of H in coplanar symmetric geometry. Phvs. Rev. A, 50: 4394, 11994 ).Google Scholar
  13. 13.
    J. Ruder, J. Rasch, K. Jung, Colm T. Whelan, H. Ehrhardt, R. J. Allan. and H. R. J. Walters, Coulomb three-body effects in low energy impact ionisation of H(1 s). Phys. Bev. A, 53: 225. (1996).Google Scholar
  14. 14.
    F. Rouet, R. J. Tweed, and J. Langlois, The effect of target atom polarisation and waver unction distortion in (e,2e) ionisation of Hydrogen. J. Phr.v. B, 29: 1767, (1996).ADSCrossRefGoogle Scholar
  15. 15.
    S.J. Ward and J.H. Macek, Wave functions for contiuum states of charged Iiagnreírls. Phys. Rer. A, 49. (1994).Google Scholar
  16. 16.
    J. Botero and J.H. Macek, Threshold angular distributions of 62.2e) cross sections of helium atoms. Phis. Rev. Lett., 68: 576 - 579, (1992).ADSCrossRefGoogle Scholar
  17. 17.
    M. Brauner, J.S. Briggs. and H. Klar, Triply-differential cross sections for ionisation of hydrogen atoms by electrons and positrons. J. Phys. B. 22: 2265 - 87, (1989).ADSCrossRefGoogle Scholar
  18. 18.
    G.H. Wannier, The Threshold Law for Single Ionization of Atoms or Ions by Electrons. Phvs. Rev., 90: 817 - 825, (1953).ADSzbMATHCrossRefGoogle Scholar
  19. 19.
    J. Berakdar and J. S. Briggs, Interference effects in (e,2e)-differential cross sections in doubly symmetric geometry. J. Phys. B, 27: 4271, (1994).ADSCrossRefGoogle Scholar
  20. 20.
    F. Gélébart and R. J. Tweed, Absolute cross sections for 100eV electron impact ionisation of helium in a symmetric energy-sharing geometry. J. Phvs. B, 23: L641, (1990).Google Scholar
  21. 21.
    A. Pochat, X. Zhang, C. T. Whelan, H. R. J. Walters, R. J. Tweed, F. Gélébart, M. Cherid, and R. J. Allan, Absolute low-energy experimental cross sections for (e,2e) processes on helium. Phys. Rev. A, 47: 3483, (1993).ADSCrossRefGoogle Scholar
  22. 22.
    J. Rasch, M. Zitnik, L. Avaldi, CoIm T. Whelan, G. Stefani, R. Camilloni, R. J. Allan, and H. R. J. Walters, A theoretical/experimental investigation of the triple differential cross-sections for electron impact ionisation of Kr(4p) and Xe(5p) at I keV impact energy. submitted to Phys. Rev. A, (1996). Google Scholar
  23. 23.
    J. Rasch.(e,2e) processes with neutral atom targets. PhD thesis, University of Cambridge, (1996). Google Scholar

Copyright information

© Springer Science+Business Media New York 1997

Authors and Affiliations

  • J. Rasch
    • 1
  • Colm T. Whelan
    • 1
  • R. J. Allan
    • 2
  • H. R. J. Walters
    • 3
  1. 1.Department of Applied Mathematics and Theoretical PhysicsUniversity of CambridgeCambridgeEngland
  2. 2.Daresbury LaboratoryWarringtonEngland
  3. 3.Department of Applied Mathematics and Theoretical PhysicsThe Queen’s University of BelfastBelfastEngland

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