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

The data obtained by Rapp, Englander-Golden, and Briglia [J. Chem. Phy s. 42, 4081 (1965)] on the dissociative-ionization fractions and cross sections for electron impact on H-2, N2, and 02 molecules have been r eanalyzed. Trajectories of the atomic ions produced in the crossed ele ctric and magnetic fields within their target cell were computed as fu nctions of ion energy and angular distribution, leading to a determina tion of how their ion-collection efficiencies depended on these parame ters. Relative ion-energy and angular distributions as functions of in cident electron energy from a variety of experimental studies were the n incorporated into the calculations to yield total collection efficie ncies, to be compared with the value of 40% estimated during the origi nal measurements. For 100-eV electrons, the comparisons indicate that the reported dissociative-ionization fractions and cross sections shou ld 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 ele ctron energies.