https://doi.org/10.1351/goldbook.C01248
A distribution of the electrons of an atom or a @M03986@ over a set of one-electron wavefunctions called @O04317@, according to the Pauli principle. From one configuration several states with different multiplicities may result. For example, the ground electronic configuration of the oxygen molecule (O2) is: \(1\sigma _{\text{g}}^{2}\), \(1\sigma _{\text{u}}^{2}\), \(2\sigma _{\text{g}}^{2}\), \(2\sigma _{\text{u}}^{2}\), \(1\pi _{\text{u}}^{4}\), \(3\sigma _{\text{g}}^{2}\), \(1\pi _{\text{g}}^{2}\) resulting in the \(^{3}\Sigma _{\text{g}}\), \(^{1}\Delta _{\text{g}}\) and \(^{1}\Sigma _{\text{g}}^{+}\) multiplets.