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The crystalline structures of the ternary halides M2BaX4 (M=Cs, Rb; X=Br, Cl), and their luminescence when doped with Eu2+ ions, are reported. These compounds crystallize with the Th3P4 body-centered cubic structure, where the Rb or Cs and Ba cations randomly occupy the Th sites in a 2:1 ratio. The Cs2BaCl4 and Rb2BaCl4 diffraction patterns show a small rhombohedral distortion from this cubic structure, which is accentuated when the compounds are prepared with excess alkali halide. When doped with divalent europium, each compound shows intense photoluminescence with a single emission band centered between 423 and 441 nm. We also find a significant photostimulated luminescence (PSL) effect in all four compounds, with an efficiency of up to 7% relative to the well-known x-ray storage phosphor BaFBr:Eu2+. The PSL effect in Rb2BaBr4 is enhanced by off-stoichiometry preparation or by fluorine doping. Attempts to prepare the related compounds MBa2X5 in single-phase form were unsuccessful. The PSL relative effic...

Previous work has demonstrated that fluorophosphate (FP) glasses doped with trivalent samarium (Sm3+) can be used as a dosimetric detector in microbeam radiation therapy (MRT) to measure high radiation doses and large dose variations with a resolution in the micrometer range. The present work addresses the use of intense optical radiation at 405 nm to erase the recorded dose information in Sm3+-doped FP glass plates and examines the underlying physics. We have evaluated both the conversion and optical erasure of Sm3+-doped FP glasses using synchrotron-generated high-dose x-rays at the Canadian Light Source. The Sm-ion valency conversion is accompanied by the appearance of x-ray induced optical absorbance due to the trapping of holes and electrons into phosphorus-oxygen hole (POHC) and electron (POEC) capture centers. Nearly complete Sm2+ to Sm3+ reconversion (erasure) may be achieved by intense optical illumination. Combined analysis of absorbance and electron spin resonance measurements indicates that the optical illumination causes partial disappearance of the POHC and the appearance of new POEC. The suggested model for the observed phenomena is based on the release of electrons during the Sm2+ to Sm3+ reconversion process, the capture of these electrons by POHC (and hence their disappearance), or by PO groups, with the appearance of new and/or additional POEC. Optical erasure may be used as a practical means to erase the recorded data and permits the reuse of these Sm-doped FP glasses in monitoring dose in MRT.

Fluorophosphate and fluoroaluminate glasses doped with trivalent samarium were evaluated as sensors of x-ray radiation for microbeam radiation therapy at the Canadian Light Source using the conversion of trivalent Sm3+ to the divalent form Sm2+. Both types of glasses show similar conversion rates and may be used as a linear sensor up to ∼150 Gy and as a nonlinear sensor up to ∼2400 Gy, where saturation is reached. Experiments with a multi-slit collimator show high spatial resolution of the conversion pattern; the pattern was acquired by a confocal fluorescence microscopy technique. The effects of previous x-ray exposure may be erased by annealing at temperatures exceeding the glass transition temperature Tg while annealing at TA

We report the photoluminescence and x-ray luminescence of lanthanum-stabilized cubic barium chloride with europium (Eu2+) doping, of general composition Ba1−x−yEuyLaxCl2+x. X-ray diffraction patterns confirm that the material adopts a cubic fluorite structure for x=0.125 and 0

We have performed numerical simulations to determine the modulation transfer function for glass ceramic x-ray imaging plates where the image readout is by a scanned laser beam. We focus, in particular, on the role of the effective scattering length in determining the width of the modulation transfer function, covering a range of scattering lengths describing very opaque to very transparent glass ceramics. We find that the shape of the modulation transfer function is, in general, bimodal, with a broad contribution from the laser beam width, and superimposed a narrow one from scattering. The overall width of the modulation transfer function reaches a minimum when the scattering length is comparable with the beam width, and so scattering lengths either much greater or less than the beam width, corresponding to either strongly scattering or highly transparent glass ceramics, give the best expected spatial resolution. However, for a practical range of scattering parameters, transparent glass ceramics are predi...

The effects of ultraviolet (UV) irradiation on the optical absorption, optically stimulated luminescence (OSL), and thermoluminescence (TL) properties of RbCdF3:Mn2+ are reported. There is a UV induced optical absorption at ∼4 eV, together with OSL and TL that are attributed to a distribution of carrier traps, as well as isolated or disconnected traps. We show that the time-integrated OSL for samples with different Mn2+ concentrations is correlated with the UV-induced change in the absorption coefficient, which we attribute to a higher trap concentration in samples with high Mn2+ concentrations. The UV-induced changes in the optical properties can be completely bleached, which leads to the possibility of holographic storage. We show that stable and rewritable thick Bragg gratings can be made in RbCdF3:Mn2+ single crystals after UV irradiation at 254 nm where the gratings were made by two beam interference at 364 nm.

We report the results of optical transmission, photoluminescence (PL), and radio-luminescence measurements on x ray, γ ray, and UV irradiated RbCdF3:Mn2+ single crystals with different Mn2+ concentrations. There is a radiation-induced increase in the optical absorption and PL intensity that correlates with the Mn2+ concentration. This suggests that the defect center that gives rise to the observed effect is associated with the Mn2+ ions. We propose that the defect center is an F-center where an electron is trapped at a fluorine vacancy situated near but not adjacent to the Mn2+ site. The PL intensity for UV (240–270nm), x-ray (

We report the results from a study of europium-doped fluorochlorozirconate glasses that have been thermally processed to induce nucleation and crystallization of BaCl2 crystallites. The resulting glass ceramics show a photostimulated luminescence (PSL) effect with a conversion efficiency which is up to 80% of that found in the commercial crystalline x-ray storage phosphor material BaFBr:Eu2+. Thermal processing for 20 min in the range 240–260 °C produces small (∼6–11nm) hexagonal BaCl2 crystallites, while temperatures in the range 270–290 °C lead to the formation and growth of larger (∼15–100nm) orthorhombic BaCl2 crystallites, as well as additional unidentified phases. We observe only weak PSL from glass ceramics containing hexagonal BaCl2 (∼0.1% conversion efficiency compared to BaFBr:Eu2+ at room temperature), but orthorhombic phase crystallites give rise to a much larger relative efficiency that increases with particle size, and reaches ∼80% for 100 nm diameter particles. The PSL is attributed to the ...