Positron and Electron Differential Elastic Cross - Measurements for Neon, Argon, Krypton, Xenon and Methane.

Relative elastic differential cross sections are measured for 5 to 300 eV positrons and electrons scattering at angles ranging from 30^circ to 134^circ for helium, neon, argon, krypton, xenon, and methane in an atom and positron crossed beam experiment. Near the argon positronium (Ps) formation threshold (9.0 eV) and neon Ps formation threshold (14.8 eV) good agreement is seen with available positron calculations. Above the Ps formation thresholds, significant differences arise between experiment and theory which are attributed to absorption effects of Ps formation on the elastic scattering channel. Good agreement is found with prior electron work.