Temporal variations in NO, N2O, and NO2 generation in filament-induced atmospheric plasmas

Abstract

Ultra-short pulse lasers generate filaments in air, inducing changes in molecular concentration and the formation of new molecules. However, our understanding of the specific chemical reactions triggered by these filaments remains limited. This study aimed to investigate the NxOy species produced by femtosecond laser filaments in a sealed chamber. We employed mid-infrared laser spectroscopy to analyze the resulting products over the reaction time. The research revealed that filament plasma generates NO, N2O, and NO2. Notably, N2O was detected for the first time in filament plasmas generated in the air. The production of NxOy species depends on the initial pressure and is influenced by factors such as plasma properties and molecular collisions. We measured the equilibrium concentrations of NO, N2O, and NO2 under atmospheric conditions, finding them to be 67, 38, and 518 ppm, respectively. Furthermore, comparative experiments conducted in zero air illustrated significantly higher concentrations of NO and NO2 under identical pressure conditions, indicating a significant negative impact of other air molecules on the generation of these species. These findings provide valuable insight into the understanding of filament-induced atmospheric chemical reactions and the generation of NxOy species.