Single and double ionization of neon, krypton and xenon by positron impact

Measurements of the single and the ratio of double to single ionization cross sections for positron impact on neon, krypton and xenon are presented from near threshold to 1000 eV. By multiplying the values of each target by the appropriate , new data for the corresponding double ionization cross sections have also been obtained. The ratio between positron and electron maxima is generally seen to be lower for higher target atomic number, as expected from the static interaction between the projectile and undistorted target. Comparison with available data suggests that Ps formation accompanied by the production of singly or doubly charged ions is a significant channel in positron - atom scattering.