Resonant collisions of electrons with O2 via the lowest-lying 2Πg state of O2−

Abstract

We report the results of an ab initio study of resonant vibrational excitation of molecular oxygen by electron impact at low energies where the lowest-lying ${}^{2}{\mathrm{\ensuremath{\Pi}}}_{g}$ resonant state of ${\mathrm{O}}_{2}^{\ensuremath{-}}$ dominantly contributes to the cross sections. The contribution of this resonance to the dissociative electron attachment cross section is also determined and the origin of its unusual oscillations is discussed. Calculations were performed within the nonlocal resonance model describing the nuclear dynamics of ${\mathrm{O}}_{2}^{\ensuremath{-}}$ after electron capture into the resonant state. The model was constructed using potential-energy curves obtained with standard quantum-chemical methods and eigenphase sums from the fixed-nuclei $R$-matrix calculations of electron scattering off ${\mathrm{O}}_{2}$. The effect of the spin-orbit interaction is taken into account when determining the potential-energy curves of the molecular negative ion. The vibrational excitation cross sections are compared with other available theoretical and experimental results.