The emission spectra of a column of a direct-current discharge in open air which is performed between two tap-water electrodes (two tap-water flows) are studied in the 240–450 nm spectral range. A comparison of the values of spectral emissivities is made between experimental spectra and the calculated spectra. The emission spectrum calculation is made for four molecules, N2, O2, NO and OH that are present in air plasma. The first part of this paper focuses on building the spectra calculation; the required data are detailed. In the second part, rotational, vibrational and excitational temperatures are determined with the Boltzmann distribution assumed on the quantum states. For that purpose, a comparison of the modelled spectra and the experimental spectra is made in the different parts of the discharge column.

Discharge with liquid non-metallic electrodes P Andre, Yu Barinov, G Faure et al. -Experimental investigations of emission spectrum of a discharge with two liquid non-metallic (tap-water) electrodes in air at atmospheric pressure P Andre, Yu A Barinov, G Faure et al. Abstract. A simple design of a plasma discharge set up, providing a stationary flow of nonequilibrium atmospheric-pressure plasma is proposed. The non-equilibrium state of plasma is maintained by using a cathode with a weakly conducting liquid like tap water. The anode is formed with a cooled metal ring-shaped inserted in a dielectric barrel. This assembly is fixed at ~ 1 cm above the water surface. The velocity of the air flow through the anode hole may be changed from 0 m/s up to ~ 10 m/s. The studied discharge in the open air gap between the tap water surface and the anode ring is powered by direct current I ~ 0.1 A. The voltage on the air gap is ≥ 1 kV. Measurements of current-voltage characteristics at different flow velocities were carried out. Spectra of radiation of the discharge column and the torch above the anode were measured. The measurement results were compared with the results of radiation spectra modeling for non-equilibrium plasma of humid air. The comparison made possible to determine the characteristics of plasma. The characteristics of the plasma depending on the speed of the airflow and the current are studied.