Formation of N2(B, v′) levels in N2, N2/Ar and N2/He reduced pressure late afterglows

The emission spectrum of nitrogen and of mixtures of nitrogen with noble gases (Ar, He) was studied and relative vibrational intensities of the nitrogen first positive (N 2 1+) system (N 2 ( B , v ′ ) → N 2 ( A , v ′′ ) + hν ) recorded between 570 and 1040 nm in the afterglow of a flowing microwave discharge at 8 Torr. In this region, N 2 ( B , v ′ ) relative populations were deduced from the recorded spectra and absolute N-atom concentrations measured by NO titration. Absolute N-atom densities were also obtained by TALIF, showing a good agreement between the two diagnostic methods. From this data, rate coefficients for the N-atom recombination in specific N 2 ( B , v ′ ) vibronic levels were obtained in N 2 and in mixtures of N 2 with Ar or He. Additionally, concentrations of N 2 ( A ), N 2 ( X , v = 12–13) molecules and of N 2 + ions were also deduced from band intensity ratios in the transition region between the pink and the late afterglows. Graphical abstract