Total-scattering cross-section measurements for intermediate-energy positrons and electrons colliding with Kr and Xe

Total-scattering cross sections have been measured in the same apparatus for positrons and electrons colliding with krypton and xenon in the energy range from 20 to 800 eV with the use of a beam-transmission technique. The unusual shapes of the peaks in the $e^{+}$-Kr and $e^{+}$-Xe total-cross-section curves suggest the possibility that inelastic processes may be contributing significantly to the respective total cross sections in those peaks. A distinct shoulder exists in the $e^{-}$-Xe total-cross-section curve in the vicinity of 20 eV, followed by a rapid decrease with the electron results dropping below the corresponding positron results in the energy range from 40 to 90 eV. This crossing of the curves at these energies is some-what anomalous compared to the situation for the other inert gases, where the electron results remain higher than the positron results. Estimates are made of potential experimental errors, including that associated with incomplete discrimination against small-angle forward scattering.