MEASUREMENTS OF TOTAL CROSS-SECTIONS FOR POSITRONS AND ELECTRONS COLLIDING WITH ATOMIC-HYDROGEN

We have measured total cross sections for 5-302 eV positrons and 31-302 eV electrons scattered by atomic hydrogen using a beam-transmission technique. Atomic hydrogen obtained from a radio frequency (rf) discharge source flows into an aluminium scattering cell maintained at about 150 K to minimize recombination. Absolute total cross sections are obtained by making relative measurements for positrons and electrons scattering from Hz and a known mixture of H and Hz, and then normalizing the measurements for positron-H-2 scattering to prior absolute measurements. Our total cross section measurements for positrons and electrons scattering from H are found to be merged to within 5% for energies from 31 to 302 eV.