Electron-impact cross sections of atomic oxygen

Abstract

We report electron-impact-induced emission cross sections forthe 2p4 3P–3s 3So(130.4 nm), 2p4 3P–3d 3Do(102.7 nm), 2p4 3P–3s′ 3Do(98.9 nm) and 2p4 3P–3s′′ 3Po(87.8 nm) transitions of atomic oxygen. Measurements were made using amagnetically confined electron beam in collision with atomic oxygen produced byan extended microwave discharge source in a crossed-beam arrangement. A 0.2 mvacuum ultraviolet diffraction spectrometer was used to record the emission. Theabsolute excitation functions of these transitions were determined by normalizing tothe O I (130.4 nm) cross section produced by dissociative excitation of O2at 100 eV impact energy (Noren et al 2001a Geophys. Res. Lett. 28 1379). A60-state model of the O I electron reaction structure has been used to extract theexcitation cross sections from the experimental measurements. The modelprocess establishes analytic collision strengths to the asymptotic limit.