Electron binding energies and how it relates to activator luminescence and bonding in compounds

Methods and models to determine the vacuum referred binding energy (VRBE) of electrons in luminescence impurity states and in host band states are briefly reviewed. Special attention is focussed on how electron bonding within anion ligands of the host compound and bonding between luminescence center and those ligands affect VRBEs, electronic properties, and luminescence properties. The chemical shift of 4f-electron VRBE, the centroid shift of 5d-electron VRBE and the Coulomb repulsion energy U for Eu appear strongly correlated with bonding and one may predict one from the other. Also conduction band and valence band energies of different compounds can be compared with each other and with reference to the common vacuum energy level. How that provides new insight in luminescence properties will be addressed. All models were derived from lanthanide spectroscopy. First results on the VRBE in transition metal impurities with single d-electron states are also reviewed.