Complexes: Electronic Spectra and Mechanism 

The observation of 2 or 3 peaks in the electronic spectra of d², d³, d⁷ and d⁸ high spin octahedral complexes needs additional treatment involving electron-electron interactions. By using the Russell-Saunders (LS) coupling scheme, these free ion configurations provide rise to F ground states that in octahedral and tetrahedral fields are split into terms designated through the symbols A_2(g), T_2(g) and T_1(g). 

To get the energies of these terms and the transition energies among them is beyond the requires of introductory level courses and is not enclosed in general textbooks. A listing of some of them is given here as an Appendix. What is essential is an understanding of how to make use of the diagrams, created to show the energy levels, in the interpretation of spectra.