Electron-impact cross sections of atomic oxygen

We report electron-impact-induced emission cross sections for the 2p(4) P-3-3s (3)Sdegrees (130.4 nm), 2p 4 P-3-3d (3)Ddegrees (102.7 nm), 2p(4) P-3-3s' (3)Ddegrees (98.9 nm) and 2p(4) P-3-3s 3Pdegrees (87.8 nm) transitions of atomic oxygen. Measurements were made using a magnetically confined electron beam in collision with atomic oxygen produced by an extended microwave discharge source in a crossed-beam arrangement. A 0.2 m vacuum ultraviolet diffraction spectrometer was used to record the emission. The absolute excitation functions of these transitions were determined by normalizing to the O I (130.4 nm) cross section produced by dissociative excitation Of O-2 at 100 eV impact energy (Noren et al 2001 a Geophys. Res. Lett. 28 1379). A 60-state model of the O I electron reaction structure has been used to extract the excitation cross sections from the experimental measurements. The model process establishes analytic collision strengths to the asymptotic limit.