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Positron - hydrogen and positronium - proton scattering at intermediate and high energies

Ratnavelu, K., Mitroy, J. and Stelbovics, A.T. (1996) Positron - hydrogen and positronium - proton scattering at intermediate and high energies. Journal of Physics B: Atomic, Molecular and Optical Physics, 29 (13). pp. 2775-2796.

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Positron scattering from atomic hydrogen is studied at energies ranging from 4 to 100 Ryd using the close-coupling approach and cross sections from both the - H and Ps - p entrance channels are reported in a basis comprising 1s, 2s and 2p states of the hydrogen and positronium atoms. Comparative studies with widely used approximation methods such as the first Born, unitarized Born and second Born approximations are presented. With the exception of elastic scattering for the Ps(1s) - p entrance channel, it was found that on-shell approximations such as the first Born and the unitarized Born approximations are reasonably accurate for collisions not involving particle transfer provided the energy is sufficiently high. Rearrangement collisions on the other hand are dominated by off-the-energy-shell scattering and the accurate approximation at high energies is the second Born approximation. Further, the effects of positronium channels on the direct reactions are investigated and we conclude that the positronium formation channels can be omitted for energies greater than 20 Ryd. Elastic scattering in the Ps(1s) - p entrance channel is seen to be unique, the high-energy behaviour of the phase shifts is different from any other quantum system.

Publication Type: Journal Article
Murdoch Affiliation: Centre for Atomic, Molecular and Surface Physics
School of Mathematical and Physical Sciences
Publisher: Institute of Physics
Copyright: 1996 The Authors
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