Total scattering cross sections have been measured in the same apparatus for positrons and electrons of well-defined energies (0.35-100 eV) colliding with krypton and xenon using a beam-transmission technique. The positron total cross sections are largest at the lowest energies studied, and decrease in a manner very similar to the elastic scattering cross-section calculations by Schrader and by McEachran et al. The total cross sections for positron-krypton, xenon collisions experience abrupt changes in their slope at the respective positronium-formation thresholds indicating that positronium formation may be an important contributor to the total cross section above the formation threshold. The present electron measurements are in good agreement with the recent measurements of Wagenaar. Estimates of potential errors in the present measurements due to incomplete discrimination against small-angle forward elastic scattering are made.

• Received 18 October 1979

DOI:https://doi.org/10.1103/PhysRevA.22.1872