Rydberg levels in carbon monoxide

Configuration interaction functions built from occupied and unoccupied LCAO-MO-SCF orbitals calculated for the 1Σ+ ground state of CO using a large basis set have been used to calculate Rydberg excited levels of 1Σ+, 3Σ+, 1Π, and 3Π symmetry. A comparison of our results with experimental data on the energy levels of Rydberg series which converge to the 2Σ+ ground state of CO+ indicates that the states E 1Σ+ and F 1Π may need re-examination; the former may be 1Π symmetry, the latter 1Π or 1Σ+. A correspondence is made between Mulliken's population analysis of our functions and the quantum defect which is deduced using the simple Rydberg formula. © 1964.