Cross-correlation spectroscopy applied to the investigation of barrier discharges in N2/O2 mixtures at atmospheric pressure

The techniques of spatially resolved cross-correlation spectroscopy (CCS) and current pulse oscillography were used to carry out systematic investigations of the barrier discharge (BD) in the binary gas mixtures N-2/O-2 at atmospheric pressure. In the case of the BD filamentary mode, which is characterized by the formation of microdischarges (MDs) of short duration, the spatio-temporal distributions of the BD radiation intensities were recorded for the spectral bands of the 0-0 transitions of the 2(nd) positive (lambda = 337 nm) and 1(st) negative system of molecular nitrogen (lambda = 391 nm). The velocities of the cathode-directed ionising waves as well as the effective lifetimes of the excited states N-2((CIIu)-I-3)(v'=0) and N-2(+)(B(2)Sigma(u)(+))(v'=0) were evaluated from the CCS data. The two-dimensional optical scanning of the MD channel (in axial and radial directions of the MD) was carried out for the BD operated in the gas mixture consisting of 6 vol.% Of 02 and 94 vol.% of N-2. In the middle of gap, the MD channel diameter was found to be about 0.3 mm and to expand towards both electrodes. On the dielectrics, outward propagating discharges were observed. In pure nitrogen the diffuse mode of barrier discharge was investigated. Surprisingly, under the conditions studied, the transition to the filamentary mode already starts for O-2 admixtures to nitrogen of > 400 ppm. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim