Single-reference electron propagator calculations on vertical ionization energies of ozone

Vertical ionization energies of ozone are calculated with electron propagator methods that employ a single reference configuration. Reference determinantal wavefunctions are defined by Hartree–Fock orbitals or by approximate Brueckner orbitals from a coupled-cluster wavefunction. An accurate description of the lowest 2A1, 2B2 and 2A2 cationic states requires retention of terms in the superoperator Hamiltonian matrix that have been safely neglected in calculations on the ionization energies of typical, closed-shell molecules.