A theoretical study of the ground state and lowest excited states of PuO^0/+/+2 and PuO₂^0/+/+2

The ground and excited states of neutral and cationic PuO and PuO ₂ have been studied with multiconfigurational quantum chemical methods followed by second order perturbation theory, the CASSCF/CASPT2 method. Scalar relativistic effects and spin-orbit coupling have been included in the treatment. As literature values for the ionization energy of PuO₂ are in the wide range of ∼6.6 eV to ∼10.1 eV, a central goal of the computations was to resolve these discrepancies; the theoretical results indicate that the ionization energy is near the lower end of this range. The calculated ionization energies for PuO, PuO⁺ and PuO₂ ⁺ are in good agreement with the experimental values.