Kinetic and Spectroscopic Constraints on the Origin of the N2 Afterglow

The large transition probability (10−1 to 10−2) for curve crossing such as that which occurs in N2 pre-dissociation, N2 (3B) ⇆N2(5Σ), guarantees that the rotationally hot members of the 12th vibrational level of the B state (3B(12))* will always be in equilibrium with free N atoms without the intervention of a third body. A kinetic scheme is suggested for these species that includes rotational and vibrational quenching in competition with electronic quenching. Fast rotational quenching gives rise to pseudoequilibrium population of normal B(12)3 species. The equilibrium constant KB for 2N⇆N2(2B(12)) is estimated at 10−1.2 liter/mole = 10−22.9 cc/particle at 300°K with a negative activation energy of − 2.2 kcal/mole, in good accord with recent data. Using 105.0±0.3 sec−1 as the measured radiative rate constant of the 12-8 transition yields an absolute emission intensity for this band of 102.9±0.3 liter/mole·sec = 10−17.9±0.3 cc/molecule·sec, again in good accord with observation. It appears from this that the 11th, 10th, and 9th vibrational levels are populated by successive collisional deactivation of the 12th level. This collisional deactivation is in competition with electronic quenching.