On the OH density distribution in an atmospheric pressure plasma interacted with liquid cathode*

The interaction of plasmas with liquids enables the generation of a broad spectrum of reactive species in the liquid phase mediated by a significant amount of species and energy transfer at the gas-liquid interface.

 

In this work, we studied spatially and temporally resolved gas-phase OH density distribution and changes in discharge morphology in the positive DC pulsed plasma interacting with liquid cathode using 2D laser-induced fluorescence (LIF) and Thomson scattering, respectively.

 

We found that the plasma contracted and OH density depleted in the core of the plasma with higher coupled discharge energy. This phenomenon coincided with both an increase in electron density and temperature. While the findings are consistent with a thermal effect, we will discuss the potential role of detachment in this process. The OH depletion in the core of the discharge is attributed to the electron impact dissociation of OH. Additionally, enhanced evaporation near the liquid even for sub-microsecond pulses was found. An analysis of the energy transfer from gas phase plasma to the liquid was made, which considered ion flux, exothermic neutral reactions, and heat flux. The calculations suggest the important contribution of ions to the total energy transfer to the solution.