Ab initio potential curves for the and states of : Existence of a double minimum

We report ab initio calculations of the X 2 Σ u + and B 2 Σ g + states of the Be 2 + dimer. Full valence configuration interaction calculations were performed using the aug-cc-pVnZ basis sets and the results were extrapolated to the CBS limit. Core–core and core–valence effects are included at the CCSDT/MTsmall level of theory. Two local minima, separated by a large barrier, are found in the expected repulsive B 2 Σ g + state. Spectroscopic constants have been calculated and good agreement is found with the recent measurements of Merritt et al. Bound vibrational levels, transition moments and lifetimes have also been calculated.