Ts. Stein et al., MEASUREMENTS OF POSITRON SCATTERING BY HYDROGEN, ALKALI-METAL, AND OTHER ATOMS, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 143(1-2), 1998, pp. 68-80
Recent developments in measurements of total and positronium (Ps) form
ation cross sections for positrons (in the energy range of 1-300 eV) s
cattered by hydrogen, alkali metal, and other atoms are reviewed. Meas
urements and calculations of total and Ps formation cross section (Q(P
s)'s) for positrons scattered by hydrogen atoms are in very good agree
ment, and for the most part there is also good agreement for sodium, p
otassium, and rubidium atoms, but there is a puzzling discrepancy betw
een measured and recently calculated Q(Ps)'s for sodium. Preliminary m
easurements of Q(Ps)'s for Mg show a very rapid rise to a large maximu
m 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 ener
gy. It appears that structure observed in e(+)-Ar and Kr Q(Ps) measure
ments may be related to capture of inner-subshell electrons. (C) 1998
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