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 31-30 2 eV electrons scattered by atomic hydrogen using a beam-transmission technique. Atomic hydrogen obtained from a radio frequency (rf) discha rge source flows into an aluminium scattering cell maintained at about 150 K to minimize recombination. Absolute total cross sections are ob tained by making relative measurements for positrons and electrons sca ttering from Hz and a known mixture of H and Hz, and then normalizing the measurements for positron-H-2 scattering to prior absolute measure ments. Our total cross section measurements for positrons and electron s scattering from H are found to be merged to within 5% for energies f rom 31 to 302 eV.