Dissociative Ionization by low energy Electron Impact. Energy Distribution and Appearance Energy of Doubly Ionized Fragments from N2 and O2.

Ion energy distributions and threshold energies are measured for the appearance of N2+ from N2. To our knowledge the same data are measured for the first time on O2+ from O2. For both ions a thermal peak is observed in the ion energy distribution having an onset at (61.1+/-0.5) eV and (60.5+/-0.8) eV for the N2+ ion and the O2+ ion respectively. The appearance energy of higher energetic ions is measured and interpreted.