The temperature dependence of the yellow glow from active nitrogen

Abstract

A discharge flow/shock tube has been used to investigate the change in emission, in the temperature range 300–1200 K, for the ν= 6, 10, 11 and 12 levels of N₂(B³Π_g) in discharged nitrogen. For each level the emission decreased with temperature and empirical equations are given to describe the behaviour. The results are interpreted qualitatively in terms of the Thrush mechanism modified to include the N₂(W³Δ_u) state. The general decrease is attributed to the fall in the third-order recombination rate constant; the detailed differences between levels are correlated with the varying energy spacings between the vibrational levels of the N₂(B³Π_g) and N₂(W³Δ_u) states. A second peak in the emission traces, attributed to the early arrival of the contact surface, is observed at much longer times than those during which the main measurements are made. It is observable only because of the inverse temperature dependence of the emission and so our experimental methods offer a unique way of studying contact surface and boundary layer processes.