Identification of higher order clusters in charge compensated materials using three-body energy transfer

Alkaline earth fluoride crystals doped with trivalent lanthanide ions exhibit defect clustering at relatively low dopant concentrations. The ions within these clusters can efficiently exchange energy with each other. These energy transfer processes are used to correlate the sites observed for one ion with those observed for another. Three-body energy transfer has been isolated in CaF2:Tb3+, Yb3+ where up-conversion cannot be achieved with normal two-body energy transfer. Only trimers or higher order clusters contribute to this up-conversion and the spectral features corresponding to these clusters can therefore be identified.