Time-resolved study of pulsed Ar–N 2 and Ar–N 2 –H 2 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, 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 (∼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 generation due to the quenching of the N 2 ( A ) metastable level by molecular hydrogen.