The characterization of radio-frequency discharge using electrolyte solution as one electrode at atmospheric pressure

Atmospheric pressure discharges driven by radio-frequency source were generated using electrolyte solution as one electrode. The electron density calculated from the Stark broadening of H-beta (486.1 nm) was in the order of 10(15) cm(-3) and showed a parabolic shape with the pH value of the solution. The simulated gas temperature increased from 950 to 2750 K as the input power increased from 12 to 40 W. We found that the plasma exposure was accompanied with the acidification of the solution electrode; it was ascribed to the dissolution of nitrogen-related compounds, such as HNO2, HNO3 and NxOy which originate from the oxidation of nitrogen in air. Also, solute atom line emission was observed in the plasma zone and evaporation was demonstrated to play an important role in the solute transport.