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The purpose of this research is to investigate the luminescence and scintillation properties of mixed halide scintillators K2LaBr5-xIx. The crystals of K2LaBr5-xIx:2% Ce (x = 0, 1, 2) have been synthesized by high-temperature solid-phase method and grown by vertical Bridgman method. The crystals are measured by X-ray induced luminescence spectra, optical transmittance photoluminescence spectrum, photoluminescence decay time, and pulse height spectrum. Under the UV and X-ray excitation, all of the crystal samples have typical Ce3+ double peaks corresponding to the energy level shifts of 5d1→2F5/2 and 5d1→2F7/2, with emission centers ranging from 350 to 400 nm. The photoluminescence decay time of the three crystals of K2LaBr5-xIx: Ce is about 20 ns. Under 662 keV γ-rays excitation from a 137Cs source, the energy resolution is 8.2%, 15% and 10% (FWHM), respectively. [ABSTRACT FROM AUTHOR]

According to the spectra of stationary X-ray excited luminescence (XEL) of BaF2: Eu nanophosphors at 80 and 294 K, it was revealed that the thermal annealing of fine-grained nanoparticles (d = 35 nm) in the range of 400–1000°C, which is accompanied by an increase of their sizes in the range of 58–120 nm, does not result in effective changes of the charge state of Eu3 + → Eu2 + activator, in contrast to CaF2: Eu nanoparticles. The maximum light output of X-ray excited luminescence of BaF2: Eu nanophosphors in the 590 nm emission band of Eu3+ ion was observed at an annealing temperature of 600°C with the average size of nanoparticles 67 nm. The subsequent growth of annealing temperatures, especially in the range of 800–1000°C, causes decrease in the light output of X-ray excited luminescence due to the increase of defect concentration in the lattice as a result of sharp increase of nanoparticle sizes and their agglomeration. In BaF2: Eu nanoparticles of 58 nm size, according to the thermostimulated luminescence (TSL) spectrum, transformation of Eu3+ → Eu2+ under the influence of long-time X-ray irradiation was revealed for the peak of 151 K. Thus, X-ray excited luminescence spectra of BaF2: Eu nanophosphors are formed predominantly due to the emission of Eu3+ ions, while emission of Eu2+ ions is observed in the TSL spectra. [ABSTRACT FROM AUTHOR]

YPO4 phosphors doped with trivalent ion Pr3+ were prepared by sol-gel method and treated with different doses of gamma radiation, from 0.25 MGy to 4 MGy. Effects of radiation on morphology, structure and luminescent properties were analyzed. Also, the influence of radiation on the change in the color of the samples was examined. The color efficiency of powders was evaluated by colorimetric analysis (CIE and L * a * b system). It has been observed that powders change color under the influence of radiation, i.e. they pass from white to pinkish red. Also, it has been determined that the radiation affects morphology change, as the particle size increases with increasing of the radiation dose. With the increase in the radiation dose, the emission intensity of samples decreases. The structure remains almost unchanged after irradiation, and the intensity constantly decreases with increasing of dose. [ABSTRACT FROM AUTHOR]

In undoped and Ce 3+ -doped LaCl 3 EPR has been detected in the X-ray luminescence (XL-EPR) in K-band (25 GHz) at 1.5 K. Two excited triplet states with different EPR parameters and spectral shapes could be separated, both triplet states have been attributed to "out-of-plane" self-trapped excitons (STE) in LaCl 3 . No EPR signals of V K centres (self-trapped holes) could be detected in undoped or Ce 3+ -doped LaCl 3 after X-irradiation at low temperatures. X-irradiation of undoped LaCl 3 creates also an EPR spectrum which can be tentatively attributed to F-type defects. The scintillation mechanism is discussed. [ABSTRACT FROM AUTHOR]

Radio-, photo- and thermo-luminescence were measured for two sets of PbWO 4 single crystal samples doubly doped with Mo and Nb 5+ /Ta 5+ ions. Pentavalent ion codoping of PbWO 4 :Mo enhances the radioluminescence intensity to the level exceeding that of BGO scintillator. However, it introduces a new trapping level, which is reflected by the intense thermoluminescence-glow-curve peak around 100 K. This trapping center is probably responsible for the increased occurrence of slow decay components in such doubly doped PbWO 4 . [ABSTRACT FROM AUTHOR]

Using electron spin resonance (ESR) and thermally stimulated luminescence (TSL) three different electron traps based on regular W sites perturbed by oxygen vacancies have been identified in PbWO 4 . Analysis of ESR spectra parameters ( g -factor values and principal axes orientations) has shown that revealed centers are (WO 3 ) - vacancy containing complex anions associated with a defect in Pb sublattice: (WO 3 ) - -A Pb complexes. One of the centers (W 1 ) is thermally stable up to 350-370 K, while the other two (W 2 and W 3 ) only to 270-290 K. Above these temperatures trapped electrons become free and recombine with localized holes, giving rise to TSL glow peaks at T\approx 323\,\hbox{K} and 365\,\hbox{K} . Using the initial rise method the 323\,\hbox{K} TSL peak-shape was fitted allowing the first order recombination kinetic that gives trap parameters E = 0.88\,\hbox{eV} and s\simeq 5\ast 10^{12}1/\hbox{s} . [ABSTRACT FROM AUTHOR]