Quenching of metastable states of atomic and molecular oxygen and nitrogen

Abstract

The quenching (or deactivation) of metastable states by atmospheric particles is studied by means of a combination of laboratory and observational data. The observational data come mainly from recent rocket measurements of the dayglow. The laboratory results of Kvifte and Vegard are considered in detail, and it is found that the quenching coefficients of O₂ for both metastable states of atomic oxygen are very small. The strong atmospheric quenching of the O red lines ( ¹D state) is found to be produced by N₂, with a coefficient approaching the gas‐kinetic value. The auroral data that gave a lower quenching rate disagree with the dayglow results and must be rejected; the difficulty is traced to contamination of low‐altitude spectra by light from higher altitudes. Only less detailed treatment of other atoms, molecules, and ions can be made; however, some conclusions are possible. Quenching coefficients seem to range from large to very small in a totally unpredictable fashion. Quenching by electrons is important in only a few special cases. The quenching of vibrationally excited O₂ and N₂ is slow enough so that significant concentrations can be built up, especially for N₂ in aurora.