An ab initio study of RbO, CsO and FrO (X2Σ+; A2Π) and their cations (X3Σ−; A3Π)

High-level [RCCSD(T)] ab initio calculations are employed to generate sets of data from which spectroscopic constants for the title species could be derived. For O, the standard aug-cc-pV5Z (no h) basis set was employed, while for the metal atoms an effective core potential combined with a large, flexible valence basis set was used. Calculated ionization energies for the metal atoms, and the calculated electron affinity of O suggest that both types of basis set are performing well. The calculated constants are, in general, in good agreement with previous experimental and theoretical studies, where available. A simple ionic model is employed to obtain ionization energies, and the resulting values are compared to those calculated at the RCCSD(T) level, as well as previous experimental values. Finally, dissociation energies of the title species are also calculated.