Laboratory studies of the mechanism of the oxygen airglow

Abstract

Two mechanisms have been proposed for the formation of the excited atomic oxygen atoms O( 1 S) that are responsible for the 557.7 nm auroral emission for the 90-100 km level of the Earth’s atmosphere. Chapman’s involves triple encounters between ground state atoms of oxygen, the other (Barth’s) involves their excitation by collisions with electronically excited molecules: O * 2 + O( 3 P) → O 2 + O( 1 S). Kinetic studies have been made of emission by O 2 ( 1 S) and by O 2 (A 3 ∑ + u , A' 3 ∆ u and c 1 ∑ - u ) in the oxygen airglow and its quenching by additives. These exclude the Chapman mechanism and support the Barth mechanism with O* 2 = O 2 (A 3 ∑ + u ), but require a significant degree of vibrational excitation ( v > 4) in the O* 2 species.