The standard and anomalous crystal-field spectra of Eu3+

The crystal-field (CF) spectra of Eu3+ in various inorganic crystalline phases are summarized based on previous investigations. A majority of experimental results can be well interpreted using a standard CF model. However, there are cases in which the spectroscopic properties and fluorescence dynamics of Eu3+ cannot be interpreted within the framework of the standard model. A particularly interesting system is Eu3+ doped into microcrystals of a charge-unbalanced host such as BaFCl. For Eu3+:BaFCl, one Eu3+ site (Site I) exhibits normal CF splitting and its energy levels and fluorescence intensity are similar to most other normal systems ever reported. A standard CF fitting has been performed for Site I. However, Eu3+ at a distorted site (Site II) is of anomalous fluorescence dynamics and CF splitting which are significantly different from those of Site I. In the metastable state of 5D0, Eu3+ ions at Site II also exhibit unusual temperature-dependent lifetime.