Production of N ₂ ( A ³ Σ u ⁺ ) in the Low-Pressure Dielectric-Barrier (Ozonizer) Discharge

Several reports in the literature imply that extremely large number densities of metastable nitrogen molecules may be found in the effluents of dielectric-barrier (ozonizer) discharges in flowing nitrogen. We have constructed a dielectric-barrier discharge which operates at 1 to 10 kV in flowing nitrogen or nitrogen mixtures with either argon or helium at total pressures between 0.3 and 6 Torr. Spectroscopic observations in the afterglow of this discharge indicate that virtually all observed excitation between 200 and 850 nm results from discharge streamers. All emissions are quenched upon adding a grounded loop downstream from the discharge. The absence of NO gamma-band emission when NO is added downstream from the grounded loop indicates that N 2 ( A) number densities in the afterglow are below 10 5 molecules cm −3 , some ten orders of magnitude below previous estimates.