On the measurement of N2(A3 sigma+u) metastable in N2 surface-Dielectric Barrier Discharge at atmospheric pressure

The N2(A3Ru sigma+µ) metastable has been investigated in an AC surface dielectric barrier discharge (surface-DBD) at atmospheric pressure in N2 by Optical-Optical Double Resonance-Laser Induced Fluorescence spectroscopy (OODR-LIF) and by Optical Emission Spectroscopy (OES). The discharge is single-side produced by metallic stripes (comb-like electrode on a dielectric layer). The OODR-LIF measurements have been carried out in space afterglow above the plasma layer. The measurement was time resolved during the AC high voltage cycle and space resolved around the metallic/dielectric stripes. The space afterglow N2(A) density does not evidence significant variation in the voltage cycle. The density is higher above the dielectric strip than on the metallic one. N2(A) density in the space afterglow has been estimated to be about 1011 cm-3. The plasma layer, not accessible by OODR-LIF, has been investigated by OES through NO-Gamma and Herman infrared bands. The estimated N2(A) maximum density in the plasma layer is higher than 1012 cm-3.