Photoelectron excitation of atomic-oxygen resonance radiation in the terrestrial airglow

Abstract

Recent laboratory measurements of the absolute cross sections for the excitation of the O I (3S) resonance state by electron impact on O and O2 when combined with in situ measurements of the photoelectron energy distribution from 120 to 300 km show that photoelectron impact is the principal excitation mechanism for λ1304-A resonance radiation in the dayglow; dissociative excitation of O2 is found to play a minor role. The laboratory measurements indicate that the 3S state is strongly populated by cascade processes and imply that the O I(3p3P → 3s3S; λ8446 A) transition should be a prominent dayglow emission feature. These experiments also show that the excitation of atomic oxygen by low-energy electron impact cannot account for the λ1304- or 1356-A emission observed in the tropical ultraviolet airglow.