Effect of voltage polarity on the plasma-liquid interactions

This letter reports on how voltage polarity affects the plasma-liquid interactions. Unique electrical characteristics are observed because of the conductive and dielectric nature of the electrolyte, which may control the accumulation and dispersion of surface charges over the liquid. Depending on the voltage polarity, distinct spatio-temporal images of the optical emissions are observed; subject to a positive voltage, sodium emissions after evaporation are observed only at the interface, while the sodium emissions are gradually transported to the discharge region because of the motion of the sodium cations in the direction of the electric field during the negative voltage phase. Changing the duty ratio clearly shows that the phenomenon is affected by the voltage polarity.