Detection of N$_{2}$(A$^{3}\Sigma ^{+}_{u})$ metastable in DBD discharge by OODR-LIF spectroscopy*

The N$_{2}$(A$^{3}\Sigma ^{+}_{u})$ metastable has been detected for first time in dielectric barrier discharge at atmospheric pressure in N$_{2}$ and N$_{2}$-O$_{2}$ gas mixtures by Optical-Optical Double Resonance --Laser Induced Fluorescence spectroscopy (OODR-LIF). The DBD discharge occurs over a thin ceramic plate on which one metallic electrode comb structured is deposited. The second electrode is a full deposit on the back of the plate external to the chamber. The N$_{2}$(A) OODR-LIF detection takes place by one laser photon tuned on the (3,0) band of N$_ {2}$(FPS) and a second one on the (2,3) band of N$_{2}$(SPS) as described in previous papers[1]. The fluorescence signal of (2,1) band of SPS is measured. The measurement is time resolved in the radiofrequency cycle (11KHz) of applied voltage and space resolved in the discharge gap. N$_{2}$(A) metastable LIF signal varies in the voltage cycle as well as with the distance (1 - 5 mm) above the surface of comb electrode. It is significantly quenched as a few percentage of O$_{2}$ is added to N$_{2}$. [1] G. Dilecce, P.F. Ambrico, S. De Benedictis, PSST (on line July 2005)