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

Pulsed surfaguide microwave discharges operating at 2.45 GHz in several Ar-N-2 and Ar-N-2-H-2 gas mixtures are studied using optical emission spectroscopy. Time-resolved measurements of Ar, N-2, N-2(+), N, and H emission lines are presented. The gas temperature, and N-2 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 N-2 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 H-2 in the mixture. Our data show that a negligible (similar to 0.2%) addition of H-2 dramatically changes the N-2 dissociation mechanism, as well as the time evolution of the emission lines during the pulse. These effects are explained by the disappearance of N-2(+) generation due to the quenching of the N-2(A) metastable level by molecular hydrogen.