SINGLE AND DOUBLE-IONIZATION OF NEON, KRYPTON AND XENON BY POSITRON-IMPACT

Measurements of the single (sigma(i)(+)) and the ratio of double to si ngle (R-2) ionization cross sections for positron impact on neon, kryp ton and xenon are presented from near threshold to 1000 eV. By multipl ying the R-2 values of each target by the appropriate sigma(i)(+), new data for the corresponding double (sigma(i)(2+)) ionization cross sec tions have also been obtained. The ratio between positron and electron sigma(i)(+) maxima is generally seen to be lower for higher target at omic number, as expected from the static interaction between the proje ctile and undistorted target. Comparison with available data suggests that Ps formation accompanied by the production of singly or doubly ch arged ions is a significant channel in positron-atom scattering.