Effect of water target on the discharge and nitric oxide (NO) generation in a cold argon plasma jet

This study aims to investigate the influence of the water target on nitric oxide (NO) production in a cold argon plasma jet, with the free jet and the glass target as the reference cases. Laser-induced fluorescence is employed to obtain spatially and temporally resolved measurements of ground state NO density. Near the gas–liquid interface, a significant enhancement of the NO density is observed, attributed to both increased energy injection and elevated OH concentration resulting from water vapor. Analysis based on the estimation of NO reaction rates indicates that the reaction between OH and N becomes an important pathway for NO formation when a water target is present. The long persistence of OH radicals during a discharge cycle allows them to fully exert their role in NO generation. These results highlight the significant role of target-induced effects in plasma chemistry and demonstrate the importance of the liquid surface in NO generation in cold plasma applications.