Accurate multireference configuration interaction calculations of the 24 Λ-S states and 60 Ω states of the BO+ cation

Abstract The potential energy curves were calculated for the 24 Λ-S states correlating with the lowest four dissociation channels of the BO + cation. The potential energy curves were also computed for the 60 Ω states generated from the 24 Λ-S states. Calculations were made for internuclear separations from 0.08 to 1.05 nm using the CASSCF method, which was followed by the icMRCI approach with the correlation-consistent basis sets. Core–valence correlation, scalar relativistic and basis extrapolation were accounted for. Of the 24 Λ-S states, only three states (2 5 Π, 1 5 Σ − , and 2 5 Σ − ) were found to be repulsive; only the 1 5 Δ state was found to be a very weakly-bound state; and the E 1 Π, 2 3 Π, and 1 5 Π states were found to be very strong bound. In addition, the B 1 Σ + and 3 1 Σ + states have double wells by the avoided crossing between the two states. The a 3 Π, 1 3 Σ − , and 2 3 Σ − states are inverted with the spin–orbit coupling effect included. The spectroscopic parameters were determined and the vibrational properties of several Λ-S states were predicted. Comparison with available experimental data shows that the methodology employed is highly accurate for this system.