Correlation of temperature fields and OH radical distributions in a gliding arc plasma

Abstract Gliding arc discharges offer a promising pathway for sustainable, electrified chemical conversion, but their complex, transient nature presents significant diagnostic challenges. Understanding the interplay between key reactive species, such as the hydroxyl (OH) radical, and the underlying temperature field is crucial for optimizing plasma chemistry, yet remains difficult to measure experimentally. This work addresses this challenge through simultaneous, single-shot structured laser illumination Rayleigh thermometry (SLIRT) and OH planar laser-induced fluorescence, quantitatively mapping both temperature and OH distributions within an atmospheric pressure air gliding arc. A key aspect of this work is the accurate determination of gas temperature via SLIRT, which requires accounting for the strong temperature dependence of the gas composition and the effective Rayleigh scattering cross-section. This correction was achieved using an iterative procedure based on local chemical equilibrium calculations, significantly refining the temperature measurement from an apparent peak near 4000 K to a corrected true temperature. The results reveal a hot, OH-depleted core with gas temperatures reaching approximately 3100 K, surrounded by a ring-like OH distribution peaking at 1500 K. This distinct spatial separation is explained by a combination of thermal and non-thermal effects: the hot core acts as a source for OH via H 2 O dissociation, while efficient non-thermal electron-impact reactions within the plasma channel create a localized sink with atoms and excited species. This integrated diagnostic approach, incorporating the rigorous temperature correction, provides unambiguous, spatially correlated data essential for validating kinetic models and advancing the understanding of non-equilibrium plasma chemistry.