R-Matrix Calculation of Electron Collisions with Molecular Oxygen in Its Electronically Excited States

Low-energy electron collisions with the X³Σ_g- ground state and a¹Δ_g and b¹Σ_g+, the Herzberg states (c¹Σ_u^-, A'³Δ_u, and A³Σ_u+), and B³Σ_u^- excited states of the O₂ molecules are studied using the fixed-nucleus R-matrix method. Integral elastic scattering and electronic excitation cross sections from the X³Σ_g^- ground state overall agree well with the available experimental and theoretical results. The electronic (de-)excitation cross sections for the electron impact with the Herzberg states and the B³Σ_u^- state are reported. The value of elastic cross sections for the six excited states decreases with the increment of electron energy, except for the resonance peaks. As the case of excitation from the X³Σ_g^- ground state, the O₂^{- 2}Π_u resonance makes a dominant contribution to the (de-)excitation cross sections from the a¹Δ_g, b¹Σ_g⁺, and the Herzberg states. The magnitude of the de-excitation cross sections at the location of the ²Π_u resonance from the Herzberg states to the ground state is about 2 to 8 times those of the excitation cross sections for the corresponding excitation transitions. These results should be significant for models of oxygen plasma and the dynamics of the Herzberg states of molecular oxygen in the earth's atmosphere.