Luminescence of calcium tungstate crystals

Fluorescence, excitation, and pulsed fluorescence measurements have been made on a single crystal of CaWO4 over a wide temperature range. The temperature dependences of the integrated fluorescence intensities and lifetimes were obtained for different excitation wavelengths. A sharp increase in the fluorescence lifetimes is observed below about 75°K and zero-phonon lines can be observed. These results are used to formulate a model for the tungstate luminescent center based on the WO42− ion in a crystal field of S4 symmetry. Energy migration and impurity trapping effects are also discussed.