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

Low-energy electron collisions with the X 3 Σ g - ground state and a 1 Δ g and b 1 Σ g +, the Herzberg states (c 1 Σ u - , A' 3 Δ u , and A 3 Σ u +), and B 3 Σ u - excited states of the O 2 molecules are studied using the fixed-nucleus R -matrix method. Integral elastic scattering and electronic excitation cross sections from the X 3 Σ 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 B 3 Σ 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 X 3 Σ g - ground state, the O 2 - 2 Π u resonance makes a dominant contribution to the (de-)excitation cross sections from the a 1 Δ g , b 1 Σ g + , and the Herzberg states. The magnitude of the de-excitation cross sections at the location of the 2 Π 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.