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In the paper the results of investigations of X-ray excitation spectra, thermostimulated luminescence and the influence of light illumination on the thermoluminescence glow curves of pure and Tb-doped PbWO4 crystals are presented. It is suggested that the F--centres are formed in PbWO4 crystals at filling oxygen vacancies near Pb3+ ions to three electrons under X-ray irradiation at 90 K. The nature of 108 K thermostimulated luminescence peak is connected with the [(WO3 + F-)-Pb3+] associations. It was established that thermal or optical destruction of this peak leads to appearance of the radiative transitions of excitons localized near the [(WO3 + F)-Pb2+] complex centres. [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]

In this paper spectroscopic investigations of Gd3Ga5O12 (GGG) polycrystals, containing Cr3+ and intentionally doped with Pr3+ of concentrations 0.5, 1 and 1.5 mol% are presented. We have measured the steady state luminescence and luminescence excitation spectra, as well as the time resolved spectra and luminescence kinetics. The main goal was to investigate the excitation energy transfer from lattice to impurity and between impurities. We found that relative intensity of Cr3+ and GGG lattice luminescence decreased when material was doped with Pr3+. On the other hand, time resolved spectroscopy and luminescence decay measurements showed that the Cr3+ and GGG lattice luminescence decays were independent of Pr3+ content. The lifetime of Pr3+ luminescence related to ¹D2→³H4 and ³P0→³H4 transitions decreased with concentration of Pr3+, which was attributed to the concentration luminescence quenching. No energy transfer between GGG lattice defects and Cr3+, and Pr3+ ions was observed. We proposed the model of radiative recombination of electron and hole, which took place through three independent pathways: by GGG host emission that peaked at 12750 cm-1, by Cr3+ luminescence that peaked at 15400 cm-1, and by Pr3+ luminescence. [ABSTRACT FROM AUTHOR]

This study explores the impact of managed care on the substance abuse service system by reviewing the current status of the programs that were among the elite service providers in 1988. A survey was conducted assessing the status of the one hundred centers touted as the 100 best treatment centers for alcoholism and drug abuse (Sunshine& Wright, 1988). Findings include the following: Almost a third of these centers (31%) are no longer providing services, the majority of the programs who reported data continue to provide services primarily at a residential level of care (92%); however occupancy rates have dropped, the number of annual inpatient admissions have risen, and the length of treatment episodes has significantly decreased. In 1988, almost all (97.5%) facilities adhered to the 28-day treatment regiment, as evidenced by average treatment episodes of 26 days or longer. However, in 2001, the majority of programs (57.5%) reported treatment episodes of 25 days or less. While these facilities represent a fraction of the number of facilities that provide substance abuse services, they do exemplify elite programs that should be insulated from economic troubles, and help to document the changes that have occurred in the delivery system. Awareness of these changes is important for every social worker that advocates for substance abuse services.