Population of N2 (B 3Πg) by N2 (A3Σu+) during the nitrogen afterglow

Abstract

The time dependence of the intensity of various emission bands during the decay period of plasmas produced in pure nitrogen was measured using the stationary afterglow method. Two processes involving the ${\mathrm{N}}_2{\mathrm{\hspace{0.17em}(A}}^3{\Sigma }_u^{+})$ metastable molecule were found to populate the N₂ (B ³Π_g) state during the nitrogen afterglow. The first process is the energy pooling reaction ${\mathrm{N}}_2{\mathrm{\hspace{0.17em}(A}}^3{\Sigma }_u^{+}\mathrm{)+}{\mathrm{N}}_2{\mathrm{\hspace{0.17em}(A}}^3{\Sigma }_u^{+}\mathrm{)\; \to }{\mathrm{N}}_2{\mathrm{\hspace{0.17em}(B}}^3{\Pi }_g\mathrm{)+}{\mathrm{N}}_2{\mathrm{\hspace{0.17em}(X}}^1{\Sigma }_g^{+})$ , which also populates the N₂ (C ³Π_u) and ${\mathrm{N}}_2{\mathrm{\hspace{0.17em}(C\prime }}^3{\Pi }_u)$ states. An approximate value for the reaction rate constant for this process was found to be ${\text{(1.1}}_{\text{−0.5}}^{\text{+2}}{\text{)× 10}}^{\text{−9}}\hspace{0.17em}{\mathrm{cm}}^3\hspace{0.17em}{\sec }^{\text{−1}}\hspace{0.17em}\mathrm{per\; molecule}$ . Strong evidence was found that N₂ (B ³Π_g) is also populated by the reaction ${\mathrm{N}}_2{\mathrm{\hspace{0.17em}(A}}^3{\Sigma }_u^{+}\mathrm{)+}{\mathrm{N}}_2^{*}\mathrm{\hspace{0.17em}(X)\to }{\mathrm{N}}_2{\mathrm{\hspace{0.17em}(A}}^3{\Sigma }_u^{+}\text{,\hspace{0.17em}v′>7)+}{\mathrm{N}}_2\mathrm{(X)\to }{\mathrm{N}}_2{\mathrm{\hspace{0.17em}(B}}^3{\Pi }_g\mathrm{)+}{\mathrm{N}}_2\mathrm{\hspace{0.17em}(X)}$ , where ${\mathrm{N}}_2^{*}\mathrm{\hspace{0.17em}(X)}$ is a vibrationally excited ground state nitrogen molecule. The population of the N₂ (B ³Π_g) energy state by recombination of nitrogen atoms was also observed.