Electron-impact studies of atomic oxygen: I. Differential and integral cross sections; experiment and theory

We report both experimental and theoretical differential and integral excitation cross sections of atomic oxygen corresponding to the 2s 2 2p 4 3 P→3s 3 S (130.4 nm), 2s 2 2p 4 3 P→3d 3 D (102.7 nm), 2s 2 2p 4 3 P→3s' 3 D (98.9 nm) and 2s 2 2p 4 3 P→3s'' 3 P (87.8 nm) transitions at 30, 50, and 100 eV electron-impact energies. Experimental measurements have been made in the angular range from 0° to 25° with a conventional electrostatic electron energy-loss spectrometer. The atomic O differential cross sections (DCSs) were put on an absolute scale by normalization to the O 2 DCS values of Johnson and Kanik (2001). Extrapolation of the measured results to larger angles was performed using theoretical calculations as a guide, and integral cross sections were derived. Theoretical calculations based on the R -matrix method, along with other available experimental data, have been compared with the current experimental results.