Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

The production of singlet delta oxygen (O-2(a(1)Delta(g))) is of growing interest for many applications. We report on the measurement of O-2(a(1)Delta(g)) and ozone (O-3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O-2(a(1)Delta(g)) production. Different O-2(a(1)Delta(g)) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as- produced and measured O-2(a(1)Delta(g)) densities are discussed. The flow rate also allows for control of the O-2(a(1)Delta(g)) to O-3 density ratio in the effluent from 0.7 to conditions of pure O-3.