On the measurement of N2(A3Σu+) metastable in N2 surface-dielectric barrier discharge at atmospheric pressure

The N-2(A(3)Sigma(+)(u)) metastable has been investigated in an AC surface dielectric barrier discharge (surface-DBD) at atmospheric pressure in N-2 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 N-2(A) density does not evidence significant variation in the voltage cycle. The density is higher above the dielectric strip than on the metallic one. N-2(A) density in the space afterglow has been estimated to be about 10(11) cm(-3). The plasma layer, not accessible by OODR-LIF, has been investigated by OES through NO gamma and Herman infrared bands. The estimated N-2(A) maximum density in the plasma layer is higher than 10(123) cm(-3).