Description of Two-Particle One-Hole Electronic Resonances Using Orbital Stabilization Methods.

Two-particle one-hole (2p-1h) resonances are elusive to accurate characterization, their decay to the neutral state being a two-electron process. Although in limited cases, single reference methods can be used, a proper description of a 2p-1h resonant state entails a multiconfigurational treatment of the reference wavefunction. In this work, we test the performance of the orbital stabilization method to characterize the 2p-1h resonances found in water and benzene. We employ a set of two multireference approaches, namely, the restricted active space self-consistent field and the multireference configuration interaction, as well as the single reference method equation of motion for electron attachment coupled-cluster with singles and doubles, in the case of benzene. We further explore the resonant channel mixing in benzene between the B shape resonance and 2p-1h resonance, a phenomenon which has been explored quite often in experimental studies.