UV–NIR spectroscopy of air plasma in transverse arc discharge

Spectroscopic characterization of a specific case of the atmospheric pressure air plasma in the transverse arc discharge of high voltage was done. Within the spectrum of wavelengths from 200 to 1100 nm all remarkable emissions were monitored, and all excited atomic lines of N, O, H and molecular bands of NO, N2, O2, OH, CN were identified. Using relative intensities of analytical CuI lines (a product of the electrode emission) and N2 (C3Πu−B3Πg) 2+-system bands (a dominating component of the plasma-forming gas), the temperature of electronic excitation of free atoms, Texc, and the temperatures of excitation of vibrational and rotational states of molecules, TV and TR, were determined. It was found that there is no local LTE in this arc discharge air plasma during its space/time evolution, and effects of strong non-isothermality have a place.