Precise measurements of positron-helium total cross sections from 0.6 to 22 eV
- 1 April 1985
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review A
- Vol. 31 (4) , 2171-2179
- https://doi.org/10.1103/physreva.31.2171
Abstract
New precise measurements for positron-helium absolute total cross sections have been performed over the energy range from 0.6 to 22 eV. A high-resolution time-of-flight spectrometer with a straight flight tube and weak axial magnetic field was designed to achieve effective reduction of forward-scattering errors. Observed results around the Ramsauer-Townsend minimum are close to the theoretical results by Campeanu and Humberston, and the remaining slight discrepancies are fully explained by taking account of incomplete discrimination against forward scattering. The results for the energy region excluding the vicinity of the minimum have been obtained with a few percent overall errors, and they are in excellent agreement with some theoretical results. The sources of systematic errors associated with the use of an axial magnetic field are clearly assessed.Keywords
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