Valence Excited States of BeO

SCF wavefunctions have been computed for the lowest 3Π and 1Π states of BeO at a number of different internuclear separations. The calculations were carried out with a carefully chosen basis set composed of 24 Slater functions. The calculated 1Π—3Π separation is very small; 923 cm−1. The spectroscopic constants and a number of one electron molecular properties for the two states are found to be very similar. This behavior is explained by the strong lone-pair characteristic of the 5σ orbital in these two states. In matching the perturbations observed in the spectrum of the singlet system, it was found that the above calculated results are consistent with the a 3Π state being one of the states that cause the ``unknown'' perturbations reported by Lagerqvist and co-workers.