Ar-N2O Microwave Plasmas and Afterglows Sustained at Atmospheric Pressure

Abstract In this study, Ar– $$\:{\text{N}}_{2}\text{O}$$ 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 $$\:{\text{N}}_{2}\text{O}$$ decomposition. The addition of $$\:{\text{N}}_{2}\text{O}$$ 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 $$\:{\text{N}}_{2}\text{O}$$ concentration results in suppression of the discharge filamentation, as well as to an increase in gas temperature, that exceeds 3000 K above 1.5% $$\:{\text{N}}_{2}\text{O}$$ . Spectroscopic and thermometric analyses confirmed effective $$\:{\text{N}}_{2}\text{O}$$ 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 $$\:\text{A}\text{r}$$ , $$\:\text{N}$$ , $$\:\text{O}$$ , $$\:\text{N}\text{O}$$ , $$\:\text{O}\text{H}$$ , and $$\:\text{N}\text{H}$$ 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– $$\:{\text{N}}_{2}$$ plasmas and postdischarges. In addition, mass spectrometry suggests $$\:{\text{N}}_{2}\text{O}$$ decomposition preferentially takes place through nitrogen-oxygen bond breaking, yielding $$\:{\text{N}}_{2}$$ , $$\:{\text{O}}_{2}$$ , and $$\:{\text{N}\text{O}}_{\text{x}}$$ products at the gas exhaust.