Direct experimental measurement of electron impact ionization‐excitation branching ratios: 2. Angular distribution of secondary electrons from N2 at 100 eV

Abstract

The coincidence ionization experiment used previously to measure ionization‐excitation branching ratios for the X ²Σg+, A ²Πu, and B ²Σu+ states of N2+ at a fixed secondary electron emission angle of 74° has been modified to allow the secondary emission angle to be scanned. Angular distributions of electrons which have excited the three available electronic states of the N2+ ion have been measured at 100 eV. For the small, primary electron scattering angles where most ionization events occur the distribution for the X ²Σg+ state is found to have a peak at 57° with respect to the incident beam direction, while that for the A ²Πu state has a broad peak near 75°. The distribution for the much less intense B ²Σu+ state is intermediate between the two. The partial branching ratios deduced for the 74° fixed angle case have been corrected to reflect the more accurate partial branching ratios obtained by integrating the secondary electron angular results. The corrected values for the X ²Σg+ A ²Πu, and B ²Σu+ states are 0.56±0.05, 0.35±0.03, and 0.09±0.02, respectively. These results show that the A ²Πu state branching ratio is much smaller than deduced from a number of previous studies