NONDISSOCIATIVE SINGLE IONIZATION OF MOLECULAR-HYDROGEN BY ELECTRON AND POSITRON-IMPACT

We present experimental results for impact ionization of molecular hyd rogen by electrons and positrons for the range of impact energies from threshold to about 2 keV (0.4-2 keV for e(-)). Our electron data agre e with the most recent ones measured by others. When we compare our po sitron results to earlier published single ionization cross sections w e find significant differences for impact energies from threshold to a bout 100 eV with the new cross sections being substantially smaller. I n the present study an effort has been made to discriminate against fa lse signals caused by positronium formation and other effects.