Electron-Impact Excitation and Ionization of Atomic Oxygen

Abstract

We utilize the analytic atomic independent-particle model (IPM) of Green, Sellin, and Zachor to calculate generalized oscillator strengths (GOS) and total cross sections for excitation and ionization of atomic oxygen. First we average over the experimental energy levels within a multiplet to arrive at single-particle levels. Then we adjust the two parameters of the IPM potential so that it accurately characterizes the ground state and 15 lowest excited states. Using the wave functions so obtained, and assuming the Born approximation and the $\mathrm{LS}$-coupling scheme, we calculate absolute GOS and cross sections for excitation to these levels, and for ionization with incident energies up to 1000 eV and secondary electron energy up to 200 eV. We obtain an analytic representation of the excitation GOS as a function of the momentum transfer. We also obtain an analytic representation of the energy differential cross section for ionization as a function of the energies of the incident and secondary electrons. Comparison is made with available experimental data and other calculations.