Electron-impact excitation/emission and photoabsorption cross sections important in the terrestrial airglow and auroral analysis of rocket and satellite observations

The UV line intensities appearing in the spectra of terrestrial auroral and airglow observational data by rockets and high altitude satellites contain important diagnostic information on energy input taking place into the thermosphere. The intensities of the observed emissions are dependent on the atomic and molecular cross sections for both electrons and photons. UV extinction weakens the emission intensity along the line-of-sight to the spacecraft and is determined by the absorption cross sections of the principal constituents: O₂, N₂[] and O. An accurate knowledge of both excitation (emission) and photoabsorption cross sections of the dominant atmospheric molecular gases (O₂ and N₂) is needed for the analysis and interpretation of rocket and satellite observations of airglow and auroral emissions. The absorption cross sections of O₂ and N₂ are difficult to measure since they are highly structured in the UV from predissociation of Rydberg and valence states. The aim of this article is to focus upon certain outstanding issues concerning the available experimental excitation (emission) and photoabsorption cross section data primarily in the far UV (FUV) spectral region. These cross sections are important to terrestrial airglow and auroral observations of N₂ and O UV emission fluorescence and to critically review the available data. (C) 2000 Elsevier Science Ltd. All rights reserved.