Chemical factors regulating free alkali metal atoms in the upper atmosphere

In contrast to dayglow and twilight emissions, which result from resonant scattering by free alkali metal atoms, the nightglow emission is probably due to chemical reaction of alkali metal compounds. It is proposed that recombination of atomic nitrogen on a metal salt particle in a dust layer is a possible mechanism leading to emission by alkali metal atoms. Weak emission from the first negative band system of N2+ may be observed concurrently. Studies on bulk meteoritic material suggest that, because of the, high recombination coefficients observed, a layer of meteoritic dust at about 90 km would greatly perturb the atomic-particle density near this altitude.