Luminescence of calcium tungstate crystals

Abstract

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.

Cryogenic scintillators in searches for extremely rare events

“…Therefore the luminescence properties of the crystals under interest have been investigated most extensively. The earlier studies have been done mainly using ultraviolet, x-ray or particle excitation [25,26,[30][31][32][33][34][35][36][37]. The results of investigations using timeresolved techniques under excitation with VUV synchrotron radiation [38][39][40], pulsed UV [41,42] and x-ray sources [43,44] have been published recently.…”

“…Tungstate and molybdate crystals have a long history of practical application as phosphors, laser hosts and scintillators [25][26][27][28][29][30]. In such applications the luminescence properties of the materials are of particular importance, and this resulted in a large number of previous research works.…”

“…At high energy the x-ray excitation (E ex > 10 3 eV) spectrum shows structureless broad band emission centred at 2.9 eV with a pronounced extension towards lower energies. This band is due to the electronic transitions of the charge transfer type within the (WO 4 ) 2− anion complex and is interpreted as an emission of self-trapped molecular excitons [30,33,34].…”

Thermally and optically stimulated processes in X-irradiated scheelite type crystals

“…This variety of similar electron centres seems to be one reason for the differences in spectral composition of the first glow peak. Considering the large Stokes shift in the luminescence of these materials [12], we expect remarkable relaxation effects in the thermoluminescence process too. For the CaW0, : Pb sample we are discussing here, the EPR results indicate ( M O O~)~-to be the recombination centre.…”

Textured silicon calorimetric light detector

“…An external 60 Co source (main photon lines at 1.17 MeV and 1.33 MeV) was used to stimulate scintillating light from the CaWO 4 (peak of emission ≈ 440 nm, FWHM ≈ 100 nm [15]). …”