Pink afterglow in nitrogen-argon mixtures

The nitrogen pink afterglow was studied by optical emission spectroscopy in the DC flowing regime at a total gas pressure of 700 Pa and at the discharge current of 120 mA. The discharge was created in a Pyrex tube of 13 mm i.d. using nitrogen and argon of 99.999% purity with additional purification by Oxiclear columns and liquid nitrogen traps. The area ±3 cm around the observation point had to be cooled down to liquid nitrogen wall temperature in order to allow the study of the reactor wall temperature effect on the post-discharge. The maximum pink afterglow emission in pure nitrogen at ambient wall temperature was observed at a decay time of 6 ms. When the argon percentage in the gas mixture was increased the pink emission maximum was shifted to the later decay times. Simultaneously, the intensity of the pink afterglow decreased and at a 1:1 nitrogen-argon ratio the effect disappeared. Similar effects were also observed when the discharge tube wall around the observation point was cooled down to liquid nitrogen temperature. The argon atomic lines were only observed during the post-discharge at the highest argon concentration at a low wall temperature. The kinetic model showed that the pink afterglow quenching was connected to the decrease of the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$v\!\!-\!\!v$\end{document} and pooling processes efficiency.