Vibrational excitation of N₂⁺(B, nu ) in He-N₂pulsed RF discharges

The authors study the excitation of N 2 + (B, nu ) in a RF pulsed discharge in low-N 2 -content He-N 2 mixtures. The decay of the ion B state density and its vibrational distribution are measured by means of time resolved emission spectroscopy of the first negative system. The Langmuir probe technique is also applied to the measurement of the electron energy distribution function. It is found that, in the conditions of the experiment, the Penning reaction with He(2 3 S) metastable is the most important excitation source of N 2 + (B, nu ). A non-Boltzmann N 2 (X, nu ) vibrational distribution is then deduced from the ion B state one.