Studies of the Nitrogen Yellow Afterglow at Low Pressures

The visible emission from the $B^3{\Pi }_g$ state of molecular nitrogen caused by the recombination of atoms has been studied in a fast flow system over the pressure range 35–1000 mtorr. Both N₂ and argon have been used as major third bodies, and investigations have been made at a number of different wavelengths. In the case of the pure nitrogen system, the results clearly show the change from second‐order to third‐order kinetics as the total pressure is decreased. Half‐quenching pressures are calculated and are in accord with the idea that electronic quenching is the main means of deactivation of the ${}^{3}B$ state. When argon is the major third body, the light emission is still pressure dependent at 1 torr, and considerably higher half‐quenching pressures are calculated. Several reaction mechanisms which might account for the observations are discussed.