Electronic excitation as a resonant process: e⁻O₂collisions

A multichannel effective range theory (ERT) of the electron impact electronic excitation via a shape resonance is presented and applied to the excitation of the a1 Delta g and b1 Sigma +g states of O2 through the O2-2 Pi g shape resonance. All the parameters required for the ERT treatment are extracted from an ab initio calculation on the O2-(2 Pi g) system. The X3 Sigma -g, a1 Delta g and b1 Sigma +g O2 states can be considered as parents of the X 2 Pi gO2- resonance and the corresponding multichannel structure is analysed. Although the O2-(2 Pi g) resonance is very narrow (8*10-5 eV) and located at very low energy (0.09 eV) at the O2 equilibrium position, it dominates the electronic excitation process in the few eV energy range. Theoretical results are presented in the 0-12 eV energy range and compared with previous experimental and theoretical results.