Kinetics of pulsed DC discharge in N$_{2}$/O$_{2}$/N$_{x}$O$_{y}$ mixtures studied by quantum cascade laser absorption spectroscopy

In this work we study the kinetics of NO, NO$_{2}$ and N$_{2}$O in a pulsed low pressure ($\sim $1.3 mbar) DC discharge in N$_{2}$ and N$_{2}$/O$_{2}$ using \textit{in-situ} QCLAS absorption. Gas mixture of 1{\%} NO, NO$_{2}$ or N$_{2}$O in pure N$_{2}$ or air is exposed to a single plasma pulse (1-10ms, 25-150 mA). In pure N$_{2}$ plasma, NO and NO$_{2}$ are destroyed completely within few ms after the beginning of the pulse. In air plasma NO$_{2}$ is transformed into NO while NO concentration reaches a steady state. N$_{2}$O destruction in both cases is 10 times slower while N$_{2}$O in the discharge undergoes strong vibrational excitation. Vibrational relaxation of N$_{2}$O in the post-discharge occurs within several 10s of ms, indicating the presence V-V$^{\mbox{'}}$ transfer from N$_{2}$(v). In this way one can use N$_{2}$O as an indicator of the excitation of IR inactive N$_{2}$ and follow the relaxation of vibrational temperature of N$_{2}$. Laser absorption measurements are strongly influenced by the effect of gas heating, so measurements of T$_{g}$ using N$_{2}$ (2$^{+})$ emission are underway.