Evidence for channel-coupling effects in positron scattering by sodium and potassium atoms

Abstract
In this letter we present measurements of total cross sections for 1-10 eV positrons scattered from sodium (Na) atoms. Comparisons of these measurements and other recent measurements of total and positronium (Ps) formation cross sections for positron-Na and potassium (K) scattering by our group with the close-coupling approximation calculations by Hewitt et al. (1993) provide rather clear evidence that coupling effects between Ps formation and other scattering channels are playing a very important role in positron scattering by Na and K.