An ab initio study of RbO, CsO and FrO (X (2)Sigma(+); A (2)Pi) and their cations (X (3)Sigma(-); A (3)Pi)

High-level [RCCSD(T)] ab initio calculations are employed to generate sets of data from which spectroscopic constants for the title species could be d erived. For O, the standard aug-cc-pV5Z (no h) basis set was employed, whil e for the metal atoms an effective core potential combined with a large, fl exible valence basis set was used. Calculated ionization energies for the m etal atoms, and the calculated electron affinity of O suggest that both typ es of basis set are performing well. The calculated constants are, in gener al, in good agreement with previous experimental and theoretical studies, w here available. A simple ionic model is employed to obtain ionization energ ies, and the resulting values are compared to those calculated at the RCCSD (T) level, as well as previous experimental values. Finally, dissociation e nergies of the title species are also calculated.