Kinetics of $A^3\Sigma_u^+$ state of molecular nitrogen in inductively-coupled nitrogen plasmas

This paper discusses the loss kinetics of the metastable $A^3\Sigma_u^+$ state of molecular nitrogen in inductively- coupled nitrogen plasmas. The loss frequency of the $A^3\Sigma_u^+$ state was evaluated from its density and the production rate. The density of the $A^3\Sigma_u^+$ state was measured by diode laser cavity ringdown absorption spectroscopy. The production frequency was estimated by evaluating the rate coefficients for electron impact excitation to the $A^3\Sigma_u^+$, $B^3\Pi_g$, and $C^3\Pi_u$ states. In the evaluations of the rate coefficients, we took into account the variation of the electron temperature, which was estimated on the basis of optical emission intensities. The variation of the loss frequency, which was evaluated from the balance between the production and loss frequencies, suggested the quenching loss of the $A^3\Sigma_u^+$ state in the gas phase. However, the loss frequency of the $A^3\Sigma_u^+$ state according to the rate coefficients of quenching processes known to date (${\rm N}_2(A^3\Sigma_u^+) + {\rm N}(^4S) \rightarrow {\rm N}_2 (X^1\Sigma_g^+) + {\rm N}(^2P)$, ${\rm N}_2(A^3\Sigma_u^+) + {\rm N}_2(A^3\Sigma_u^+) \rightarrow {\rm N}_2(B^3\Pi_g) + {\rm N}_2(X^1\Sigma_g^+)$, and ${\rm N}_2(A^3\Sigma_u^+) + {\rm N}_2 (A^3\Sigma_u^+) \rightarrow {\rm N}_2(C^3\Pi_u) + {\rm N}_2(X^1 \Sigma_g^+)$) are smaller than the diffusion loss frequency. Further investigations are necessary to identify the dominant loss process of ${\rm N}_2(A^3\Sigma_u^+)$ in nitrogen plasmas.