DISSOCIATIVE IONIZATION OF H-2, N2, AND O2 BY ELECTRON-IMPACT

The data obtained by Rapp, Englander-Golden, and Briglia [J. Chem. Phys. 42, 4081 (1965)] on the dissociative-ionization fractions and cross sections for electron impact on H-2, N2, and 02 molecules have been reanalyzed. Trajectories of the atomic ions produced in the crossed electric and magnetic fields within their target cell were computed as functions of ion energy and angular distribution, leading to a determination of how their ion-collection efficiencies depended on these parameters. Relative ion-energy and angular distributions as functions of incident electron energy from a variety of experimental studies were then incorporated into the calculations to yield total collection efficiencies, to be compared with the value of 40% estimated during the original measurements. For 100-eV electrons, the comparisons indicate that the reported dissociative-ionization fractions and cross sections should be increased by about 15% for N2 and 02 targets, but by almost 70% for H-2 targets, with all corrections increasing markedly at lower electron energies.