Near-Threshold Ionization of He and H{sub 2} by Positron Impact
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
The single ionization cross sections for He and H{sub 2} by positron impact have been measured in the first few eV above threshold and found to exhibit a different energy dependence from the corresponding electron results. If the data, between 1 and 3eV above threshold, are fitted by a power law, exponents of 1.99{plus_minus}0.19 and 1.70{plus_minus}0.11 are obtained for He and H{sub 2}, respectively. This agrees qualitatively with extensions of the Wannier theory in that the exponent is larger than for electron impact. The quantitative disagreement with the predicted value of 2.65 might indicate that the range of validity of this theory is smaller than expected. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 286979
- Journal Information:
- Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 7 Vol. 77; ISSN 0031-9007; ISSN PRLTAO
- Country of Publication:
- United States
- Language:
- English
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