Stark broadening and shift of hydrogenic and non-hydrogenic lines for the electron density determination in pulsing discharges in contact with liquids

Pulsed discharges in contact with liquids have found many applications in various fields such as degradation of hazardous contaminants in water, bio decontamination, agriculture, combustion and chemical synthesis. The expansion of these discharges urges the development and validation of fast, simple and non-intrusive methods for the diagnostics for the sake of discharge optimization and the identification of action mechanisms. Optical emission spectroscopy is a traditional method that may meet all mentioned requirements. In the present article, spectroscopic methods based on the Stark broadening and shift of hydrogenic and non-hydrogenic lines for the determination of the electron densities above 1016 cm−3 are summarized and tested. Methods based on the hydrogen Balmer alpha and beta lines are elaborated and commented on. Also, the use of argon, oxygen and nitrogen lines for the electron concentration measurements is proposed and the appropriate relations and parameters are given. All proposed methods are tested and compared using self-pulsing discharge with liquid electrodes in argon and air. Finally, the validity of the temporally unresolved measurements and the two-fit method are commented on.