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Coupling between positron-atom scattering channels above the first inelastic threshold
P G Coleman1, N Cheesman, E R Lowry
1Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom.
Physical Review Letters
|June 13, 2009
Summary
Positron scattering on argon and xenon shows a step-like increase at positronium formation energy. This suggests a virtual positronium state, differing from theoretical predictions of cusp-like behavior.
Area of Science:
- Atomic and Molecular Physics
- Quantum Scattering Theory
- Positron-Atom Interactions
Background:
- Elastic scattering cross sections are fundamental in atomic physics.
- Theoretical models predicted cusp-like behavior in positron scattering near inelastic thresholds.
- Positronium formation is a key inelastic process.
Purpose of the Study:
- To experimentally determine positron scattering cross sections for argon and xenon.
- To investigate the behavior of elastic scattering near the positronium formation threshold.
- To compare experimental findings with theoretical predictions.
Main Methods:
- Experimentally measured elastic scattering cross sections.
- Utilized positron scattering experiments on noble gas targets (argon, xenon).
- Analyzed scattering data at energies corresponding to the first inelastic threshold.
Main Results:
- Observed a distinct steplike increase in elastic scattering cross sections.
- This feature was more pronounced in xenon than in argon.
- The observed behavior deviates from theoretically predicted cusp-like features.
Conclusions:
- The steplike increase suggests the presence of an intermediate virtual positronium state.
- This virtual state appears to enhance the elastic interaction probability.
- Experimental results challenge existing theoretical models for positron scattering near thresholds.
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