Abstract
Recent developments in measurements of total and positronium (Ps) formation cross sections for positrons (in the energy range of 1–300 eV) scattered by hydrogen, alkali metal, and other atoms are reviewed. Measurements and calculations of total and Ps formation cross section ( Q Ps's) for positrons scattered by hydrogen atoms are in very good agreement, and for the most part there is also good agreement for sodium, potassium, and rubidium atoms, but there is a puzzling discrepancy between measured and recently calculated Q Ps's for sodium. Preliminary measurements of Q Ps's for Mg show a very rapid rise to a large maximum value less than 2 eV above the Ps formation threshold energy (0.8 eV) which may be related to the proximity of that threshold to zero energy. It appears that structure observed in e +–Ar and Kr Q Ps measurements may be related to capture of inner-subshell electrons.
Published Version
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