. The calculations were performed with the bond length RC-O = 1.1621 Å . The bound state orbitals were computed using an aug-cc-pVTZ basis using MOLPRO with a valence complete-active-space self-consistent field (VCASSCF) description of the ground state keeping the C(1s) and O(1s) core orbitals doubly occupied in all configuration state functions. In the photoionization calculation, the initial state was represented by a configuration interaction wave function with the three core orbitals doubly occupied and including up to quadrupole excitation into the weakly occupied orbitals from the VCASSCF calculation. The initial Σ 𝑔 + 1 state used to compute the dipole matrix elements was then obtained using triple excitations into the weakly occupied orbitals. In the scattering calculations, the ionization potentials for the four ion states were adjusted to agree with experimental values of 13.78 eV, 17.31 eV, 18.08 eV, and 19.39 eV for the 𝑋 ̃, 𝐴 ̃, 𝐵 ̃, and 𝐶 ̃ states, respectively . The resulting cross sections contained a number of autoionizing resonance structures, which were analyzed by fitting the line shapes to Fano profiles to extract the position and the width of each autoionization resonance.