 Tanabe–Sugano diagram

A plot of many-electron ligand-field term energies relative to the ground state against a normalized ligand-field strength. Axes commonly use $E/B$ and ${\Delta }_o/B$, with the ratio of other interelectronic parameters stipulated. A change of ground-state term can create a break in the plotted reference.

The Tanabe–Sugano diagram is a graphical representation used in the field of coordination chemistry and solid-state chemistry to illustrate the energy levels of electronic states in transition metal complexes. It is particularly useful for understanding the effects of ligand field splitting on the d-orbitals of transition metal ions as they interact with ligands.