Mechanistic insights into air discharge mode transition: Revealing the indispensible roles of N_{2}(v) and N_{2}O_{5}.

Abstract

The phenomenon of discharge mode transition in air plasmas, which refers to the selective production of reactive species under different external conditions, has been a longstanding issue and has regained major attention recently due to emerging plasma applications. In this letter, we present a novel kinetic model that incorporates both vibrational N_{2} kinetics and N_{2}O_{5} dissociation reactions in plasma chemistry. This model describes the experimental results of discharge mode transition self-consistently, which has not been achieved before. It is found that both power- and temperature-triggered discharge mode transitions are directly induced by the enhanced recombination of NO and NO_{2} to quench O and O_{3}. Two distinct pathways for NO and NO_{2} production are identified: high discharge powers sustaining the excitation of N_{2} to high vibrational levels and elevated gas temperature accelerating N_{2}O_{5} dissociation. Essentially, both species are indispensable for enabling discharge mode transition, as their absence leads to significant deviations in transition dynamics. These results explain the origin and kinetics of discharge mode transition and contribute to further advancing plasma applications.