Abstract
The excitation of the 3s'' 3P° and 2s2p 53P° autoionizing states of OI by electron impact on atomic oxygen has been studied. Absolute cross section values from threshold to 300 eV have been obtained for the 3s'' 3P° state. Limited emission cross section data for the 2s2p 53P° and other partially radiating autoionizing states were also obtained at an impact energy of 100 eV. These results suggest that the excitation of the OI autoionizing states account for ≈33% of the total O + total ionization cross section at 40 eV under optically thin conditions and that the cross section ratio, σ( 4S)/σ( 2D + 2P), has been underestimated substantially in earlier theoretical work. Electron-impact excitation of the 3s'' 3P° and 2s2p 53P° states in an optically thick medium enhances the effective total ionization cross section for atomic oxygen by ≈15% and increases the specific O +( 4S) production rate by ≈25% with important implications for O + ion chemistry in gaseous discharges and planetary ionospheres.
Published Version
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