VIBRATIONAL DISTRIBUTION OF N2(-EV ELECTRON-IMPACT ON N-2() A(2)PI(MU) FROM 100)

Measurements of the electron excitation of the Meinel band system of N 2+ produced by electron impact on N2 have been hampered by the long li fetime of the N2+ A 2PI(u) upper state, the spectroscopically inconven ient near-infrared region where the bands are located, as well as over lap by the N2 first positive system. In the present work, an experimen t in which the scattered projectile electron and the low-energy second ary electron are detected in coincidence was used to allow the vibrati onal distribution of the A 2PI(u) State produced by 100-eV electron im pact on N2 to be determined directly in excitation without the need fo r optical measurements. The coincidence energy loss spectrum was measu red for a typical secondary electron energy of 5 eV over a range of se condary electron ejection angles. The results of a band contour analys is show that the population of the v'=0-5 vibrational levels is consis tent with that predicted by the Frank-Condon factors for ionization of N2 to the N2+ A 2PI(u) state.