Plasma-Induced Excitation and Electron Density Characterization in Atmospheric Cyclonic Discharges via Stark Broadening Spectroscopy

This study introduces the spectroscopic diagnostic approach for characterizing key energetic parameters—electron density and electronically excited temperature—in cyclonic plasma operating at atmospheric pressure. Employing Stark broadening analysis, electron densities were quantitatively determined from the Hα (656.1 nm) and Ar I (696.54 nm) emission lines in both pure argon (Ar) and argon–water (Ar/H2O) plasmas. The emission line profiles were deconvoluted to isolate Stark contributions, revealing spatially resolved plasma densities: surface electron density derived from Hα broadening (0.38 × 1015 cm–3) and bulk electron density from Ar I broadening (2.26 × 1015 cm–3). Electronically excited temperatures were evaluated using the Boltzmann plot method, yielding values of approximately 5153.74 K (Ar) and 7196.54 K (Ar/H2O). This methodology enables precise spatial diagnostics of energetic electron populations in chemically active, high-pressure discharges and provides critical insights into plasma-assisted excitation and ionization processes relevant to advanced high-energy chemical applications, such as radical generation, molecular fragmentation, and plasma discharge chemistry.