Ar-N2O Microwave Plasmas and Afterglows Sustained at Atmospheric Pressure

In this study, Ar– \:N₂O discharges sustained by a surfatron device operated at atmospheric pressure were investigated to elucidate their physicochemical behavior and potential for reactive oxygen and nitrogen species (RONS) generation through \:N₂O decomposition. The addition of \:N₂O to an argon plasma led to a shortening of the plasma column and the appearance of a diffuse afterglow region that extends to long distances (> 50 cm). Increasing \:N₂O concentration results in suppression of the discharge filamentation, as well as to an increase in gas temperature, that exceeds 3000 K above 1.5% \:N₂O . Spectroscopic and thermometric analyses confirmed effective \:N₂O dissociation and the formation of RONS in the discharge. The afterglow, characterized by long-lived metastables and excited argon, nitrogen, and oxygen species, exhibited progressively decreasing temperatures, reaching below 100 °C. Optical emission analysis in this zone revealed rich \:Ar , \:N , \:O , \:NO , \:OH , and \:NH spectra, from which dissociation pathways and kinetic mechanisms have been proposed. A simplified kinetics scheme to elucidate the behavior of these plasmas is proposed, and the results are compared to those obtained with Ar– \:N₂ plasmas and postdischarges. In addition, mass spectrometry suggests \:N₂O decomposition preferentially takes place through nitrogen-oxygen bond breaking, yielding \:N₂ , \:O₂ , and \:NOₓ products at the gas exhaust.