The variations of the spectra introduced by states derived from a singly occupied d-type orbital led us to consider four types of OCCs. The molecular analog of the atomic 2 P → 2 S transition was deemed not promising (see Section III A in the SI). Among the low-lying states we considered the transitions between the first excited and the ground states, separately for q ν i ν f sum q 00 0.916 0.9165 q 01 0.082 0.9985 q 02 0.000 0.9987 q 03 0.000 0.9989