Time-resolved study of pulsed Ar–N2 and Ar–N2–H2 microwave surfaguide discharges using optical emission spectroscopy

Abstract

Pulsed surfaguide microwave discharges operating at 2.45 GHz in several Ar–N2 and Ar–N2–H2 gas mixtures are studied using optical emission spectroscopy. Time-resolved measurements of Ar, N2, , N, and H emission lines are presented. The gas temperature, and N2 rotational and vibrational temperatures are also analyzed. Various discharge conditions, dependent on the applied power, discharge pressure, nitrogen and hydrogen content are examined. Time-resolved measurements confirm that N2 dissociation in the discharge depends mainly on the presence of nitrogen ions (dissociative recombination). Gas temperature is found to be a power-dependent parameter, whereas vibrational temperature is mainly determined by nitrogen content and by the presence of H2 in the mixture. Our data show that a negligible (∼0.2%) addition of H2 dramatically changes the N2 dissociation mechanism, as well as the time evolution of the emission lines during the pulse. These effects are explained by the disappearance of generation due to the quenching of the N2(A) metastable level by molecular hydrogen.