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In this work the researched results of the spectral characteristics of the luminescence and the thermostimulated luminescence curves of Y2O3 and Y2O3:Eu ceramic materials at the X-ray excitation in the 85-295 K range were generalized. Considering the features of Y2O3 crystal structure and the possibility of the formation of the short-lived and stable hole and electron centers of V- and F-type by the ionizing radiation X-ray luminescence spectrum of ceramics at 85 K is fitted into the elementary Gaussian shape bands with the maxima near 3.40, 3.06, 2.67, 2.33, 2.09, and 1.91 eV. The main 3.40 and 3.06 eV bands of the luminescence are caused by the self-trapped excitons of (YO6)9- complex, when the cation is localized in the field of the trigonal (C3i) and monoclinic (C2) symmetries. The emission at 2.67 eV and the weak bands in the 1.65-2.61 eV region are considered as the radiation of excitons localized on the anion vacancies and the electron centers of F-type (F+, F and F-). The thermoluminescence of Y2O3 in the 186 and 204 K main peaks range is connected with the thermal destruction of the self-trapped states of O- ions that located in the field of the trigonal and monoclinic symmetries. The activator bands caused by 5D → 7Fj electronic transitions in Eu3+ are only observed in the X-ray and thermostimulated luminescence spectra of Y2O3:Eu ceramics. It was assumed that both at the X-rays irradiation and an optical excitation in the band of the charge transfer of Y2O3:Eu sample the energy goes to Eu3+ through (Eu2+O-) complexes (states) of the charge transfer. [ABSTRACT FROM AUTHOR]

In this work the researched results of the spectral characteristics of the luminescence and the thermostimulated luminescence curves of Y2O3 and Y2O3:Eu ceramic materials at the X-ray excitation in the 85-295 K range were generalized. Considering the features of Y2O3 crystal structure and the possibility of the formation of the short-lived and stable hole and electron centers of V- and F-type by the ionizing radiation X-ray luminescence spectrum of ceramics at 85 K is fitted into the elementary Gaussian shape bands with the maxima near 3.40, 3.06, 2.67, 2.33, 2.09, and 1.91 eV. The main 3.40 and 3.06 eV bands of the luminescence are caused by the self-trapped excitons of (YO6)9- complex, when the cation is localized in the field of the trigonal (C3i) and monoclinic (C2) symmetries. The emission at 2.67 eV and the weak bands in the 1.65-2.61 eV region are considered as the radiation of excitons localized on the anion vacancies and the electron centers of F-type (F+, F and F-). The thermoluminescence of Y2O3 in the 186 and 204 K main peaks range is connected with the thermal destruction of the self-trapped states of O- ions that located in the field of the trigonal and monoclinic symmetries. The activator bands caused by 5D → 7Fj electronic transitions in Eu3+ are only observed in the X-ray and thermostimulated luminescence spectra of Y2O3:Eu ceramics. It was assumed that both at the X-rays irradiation and an optical excitation in the band of the charge transfer of Y2O3:Eu sample the energy goes to Eu3+ through (Eu2+O-) complexes (states) of the charge transfer. [ABSTRACT FROM AUTHOR]

The luminescent properties of CdWO4:Tb,Li crystals have been investigated at 10 K in the region 4-25 eV using synchrotron excitation. It is shown that besides the intrinsic matrix luminescence the number emission lines due to electron f-f-transitions in Tb3+ ions are eficiently excited at near-edge region of the fundamental absorption (Eexc = 4:1 eV). The weak recombination luminescence of terbium impurity on the background of intensive matrix luminescence is observed under excitation in the region of fundamental absorption (Eexc = 5:4 and 13.8 eV). It is shown that the luminescence spectrum of the matrix is a superposition of three elementary bands 2.07, 2.47, and 2.73 eV. The nature of emission bands is discussed. [ABSTRACT FROM AUTHOR]

We have studied the effect of lead dopant on the optical absorption, photoluminescence, and x-ray luminescence spectra, and the scintillation characteristics of CdI2 at room temperature. The crystals for the study were grown by the Stockbarger-Bridgman method. Activation of CdI2 from the melt by the compound PbI2 leads to the appearance in the absorption spectra in the near-edge region of an activator band at 395–405 nm, which is interpreted as an A band connected with electronic transitions from the 1S0 state to the 3P1 levels in the Pb2+ ion. For x-ray excitation, CdI2:Pb2+ crystals with optimal dopant concentration (∼1.0 mol%) are characterized by a light yield with maximum in the 570–580 nm region that is an order of magnitude higher than for CdI2 crystals in the 490–500 nm band. For α excitation, the radioluminescence kinetics for cadmium iodide is characterized by a very short (∼0.3 nsec) rise time and fast decay of luminescence, with τ1 ≈ 4 nsec and τ2 = 10–76 nsec. Depending on the conditions under which the crystals were obtained, the fast component fraction is 95%–99%. The crystal is characterized by a similar scintillation pulse in the case of excitation by x-ray pulses. The radioluminescence pulse shape for CdI2:Pb in the decay stage is predominantly exponential, with luminescence decay time constants τ1 ≈ 10 nsec and τ2 = 200–250 nsec. This system is characterized by low afterglow, at the level for the Bi4G3O12 scintillator. We have demonstrated the feasibility of using CdI2:Pb as a scintillator for detecting α particles. [ABSTRACT FROM AUTHOR]

We systematize earlier and new data on the effect of oxygen and hydrogen impurities on recombination processes in CaI2 crystals by jointly examining their roentgeno-, thermo-, and photostimulated luminescence spectra. The 90-K emission spectra of CaI2 crystals are shown to consist of at least five bands. The 395-nm emission is assumed to be due to radiative decay of (HI)* heteronuclear excitons. The 520-nm luminescence is attributable to iodine-vacancy-bound anion excitons. The thermostimulated luminescence peaks observed in the temperature range 90–150 K are due to the thermal dissociation of V k and H hole centers. The 90-K photostimulated luminescence of CaI2-based crystals is shown to be excited in the electronic stage of the recombination process. [ABSTRACT FROM AUTHOR]

The roentgenoluminescence spectra, temperature-dependent activator luminescence, optically stimulated luminescence, and the effect of IR irradiation on the yield and spectral composition of the low-temperature roentgenoluminescence and thermoluminescence curves of the Y3Al5O12:Ce3+ scintillator have been studied in the temperature range 85–295 K. The results, coupled with earlier data, suggest that the Ce3+ ions in the garnet crystal studied form Ce3+ p hole centers and increase the concentration of electronic F −-centers responsible for the IR stimulation band at 940 nm. The reduction in roentgenoluminescence yield on cooling Y3Al5O12:Ce3+ to below 230 K is due to the significant localization of excited carriers at defects, which show up in thermoluminescence peaks and optical stimulation spectra. The low-temperature Ce3+ luminescence in Y3Al5O12:Ce3+ seems to result from the recombination of activator-bound excitons. [ABSTRACT FROM AUTHOR]

Luminescent properties of PbI[sub 2] and PbI[sub 2]: 0.5 mol % MnCl[sub 2] crystals under X-ray or N[sub 2]-1aser excitation are studied experimentally. The measurements are performed at temperatures ranging from 85 to 295 K. For PbI[sub 2] crystals under laser excitation, spectral bands with peaks near 495 and 512 nm, respectively, are observed at 85 K. With X-ray excitation at the same temperature, luminescence is observed in the 515- and 715-nm bands. The doping decreases the intensity in the 515-nm band, increases it for longer wavelengths, and shifts the highest peak to 700 nm. At 85 K, the doping has an insignificant effect on the excitation energy accumulated by trapped electrons. Certain PbI[sub 2] crystals also exhibit a peak in a region of 580-595 nm. This peak becomes much higher if the crystal is treated with an N[sub 2] laser at room temperature or if it is heated to 450485 K. As the measurement temperature rises from 85 to 295 K, luminescence intensity decreases considerably. With X-ray excitation at room temperature, the yield of PbI[sub 2]: Mn luminescence peaked at 660 nm for doped crystals is about three times larger than the yield peaked at 555 nm for nondoped crystals. The spectral curves and underlying radiative processes are discussed. [ABSTRACT FROM AUTHOR]

Thermo- and photostimulated luminescence of CaI[sub 2] : Tl and CaI[sub 2] : Pb scintillation crystals under optical and X-ray excitation is studied. It is shown on the basis of the results obtained with account for the data of studies of photo- and X-ray -luminescent properties of these scintillators that T1[sup +] and Pb[sup 2+] ions form complex capture centers with host defects. These centers are responsible for the thermostimulated luminescence in the temperature range of 150-295 K, and the centers of charge carrier trapping are spatially separated from the centers of recombination emission. An assumption is made that thermo- and photostimulated luminescence of CaI[sub 2] : Tl and CaI[sub 2] : Pb crystals under optical excitation is observed mainly due to the delocalization of charge carriers from hydrogen-containing centers responsible for the excitation band at 236 nm and the photoluminescence of CaI[sub 2] with a maximum at 395 nm. The luminescence of CaI[sub 2] : Tl crystals in the 510-nm band and CaI[sub 2] : Pb crystals in the 530-nm band is determined by the radiative decay of near-activator excitons. [ABSTRACT FROM AUTHOR]