The structural and luminescence properties of Lu x Y 1 − x BO 3 solid solutions doped with Ce 3+ or Eu +3 have been investigated. It has been found that the solid solutions crystallize in the vaterite phase with a lutetium concentration x < 0.5. For a higher lutetium concentration x , the solid solutions contain an additional calcite phase with a content less than 5 wt %. The luminescence spectra are characterized by intensive impurity emission under excitation with the synchrotron radiation in the X-ray and ultraviolet spectral ranges. It has been shown that, as the lutetium concentration x in the Lu x Y 1 − x BO 3 : Ce 3+ solid solutions increases, the emission intensity smoothly decreases, which is associated with a gradual shift of the Ce 3+ 5 d (1) level toward the bottom of the conduction band, as well as with a decrease in the band gap. It has been established that, in the Lu x Y 1 − x BO 3 : Eu 3+ solid solutions with intermediate concentrations x , the efficiency of energy transfer to luminescence centers increases. This effect is explained by the limited spatial separation of electrons and holes in the solid solutions. It has been demonstrated that the calcite phase adversely affects the luminescence properties of the solid solutions.

It is shown that the light output of ZnxMg1-xWO4 solid solutions has a maximum at x = 0.5 under X-ray excitation. Excitation spectra of exciton emission under vacuum ultraviolet excitation also show the increase of the probability of exciton creation by the geminate e-h pairs for the intermediate values of x. Numerical simulation of the relaxation of hot electrons and holes demonstrates that the observed effects are due to the decrease of the mean distance between thermalized charge carriers. (C) 2014 Elsevier B.V. All rights reserved.

The intensity of undulator radiation, distortion of the spectrum, and the broadening of spectral lines of a planar undulator with a constant component of the magnetic field on its axis are studied using the technique of generalized special functions. Based on the obtained mathematical solutions, it is shown how the choice of certain values of the undulator parameters makes it possible to decrease the distortions of its radiation spectrum. The dependence of distortion of the spectral lines on the number of periods, the magnetic field, and other undulator parameters is determined analytically. The broadenings of the spectral lines caused by homogeneous and inhomogeneous effects produced by the constant-field components in undulators are compared. The possibility of the influence of the Earth’s magnetic field on the radiation of an undulator with a large number of periods is analyzed.

This paper reports on the results of an investigation into the luminescence properties of yttrium and lutetium borates, as well as the Y0.35Lu0.65BO3 solid solution, under excitation with the synchrotron radiation in the X-ray and ultraviolet spectral ranges. It has been shown that there exists an intrinsic luminescence band in the ultraviolet spectral range 260–270 nm due to the luminescence of self-trapped excitons. It has been found that the kinetic characteristics of this band depend on the density of the exciting synchrotron radiation. A number of luminescence bands have been observed in the long-wavelength range due to the presence of defects in the crystal structure of borates. It has also been shown that the energy transfer to impurity centers has a recombination nature and can also occur through impact ionization of defects. It has been revealed that, for the solid solution, the excitation efficiency of the luminescence of defects increases under interband excitation, which can be associated with the limited separation of the components of an electron-hole pair as a result of short-range order disturbance in the structure of the solid solution.

Charge carrier trapping centers have been studied in molybdates CaMoO4, SrMoO4 and PbMoO4 with the scheelite crystal structure as well as in ZnMoO4, which crystallize in a-ZnMoO4 structural type. The trap parameters such as activation energies and frequency factors have been determined. It is shown for the first time that both electrons and holes are trapped by the elements of regular crystal structure in ZnMoO4. The effect of the charge carrier trapping on luminescence properties is demonstrated. Potential influence of the traps on the scintillation process is discussed. (C) 2013 Elsevier B.V. All rights reserved.

¥ÏËÕÓËÌ £ÎÂAEËÏËÓÑÄËÚ ÒÓËAEÂÄÂÎ ÑÚÇÐß ÃÑÎßÛÑÇ ÊÐÂÚÇÐËÇ ÒÑÒÑÎÐÇÐËá ÃËÃÎËÑÕÇÍË ¯ªªÁ ¶ ÐÇÑÃØÑAEË-ÏÞÏË ÉÖÓÐÂÎÂÏË Ë ÍÐËÅÂÏË.¥.£.³ÍÑÃÇÎßÙÞÐ ÒÑ AEÑ-ÅÑÄÑÓÈÐÐÑÔÕË Ô ÓÖÍÑÄÑAEÔÕÄÑÏ ±¤µ ( ÊÂÕÇÏ ®ËÐÔÓÇAE-ÏÂÛÂ) ÑÓÅÂÐËÊÑÄÂÎ ÍÑÏÒÎÇÍÕÂÙËá ËÐÑÔÕÓÂÐÐÞØ ÉÖÓÐÂ-ÎÑÄ Ë ÍÐËÅ AEÎâ ÃËÃÎËÑÕÇÍË ËÐÔÕËÕÖÕ Ê ÔÚÈÕ ÄÂÎáÕÐÞØ ÔÓÇAEÔÕÄ àÕËØ ÑÓÅÂÐËÊÂÙËÌ.³ÑÔÕÂÄÎÇÐËÇ ÔÒËÔÍÑÄ, ÐÇÑÃØÑ-AEËÏÞØ AEÎâ ÊÂÍÂÊ ÉÖÓÐÂÎÑÄ Ë ÍÐËÅ, ÑÐ ÒÑÓÖÚËÎ ª.³.ºÂ-ÒËÓÑ Ë ÓÇÅÖÎâÓÐÑ ÑÃÔÖÉAEÂÎ ÄÔÇ ÄÑÊÐËÍÂÄÛËÇ ÄÑÒÓÑÔÞ.¥ÏËÕÓËÌ £ÎÂAEËÏËÓÑÄËÚ ÄÔÇÅAE ÔÚËÕÂÎ, ÚÕÑ ÄÑÒÓÑÔÞ ÑÓÅÂÐËÊÂÙËË ÐÂÖÚÐÑÌ ÓÂÃÑÕÞ Ë ÖÚÇÃÐÑÅÑ ÒÓÑÙÇÔÔ AEÑÎ-ÉÐÞ ÓÇÛÂÕßÔâ Ô ÒÓÑâÄÎÇÐËÇÏ ËÐËÙËÂÕËÄÞ Ë ÐÂÒÑÓËÔÕÑ-ÔÕË Ä AEÑÔÕËÉÇÐËË ÒÑÔÕÂÄÎÇÐÐÑÌ ÙÇÎË,  ×ÑÓÏÂÎßÐÞÇ ÄÑÒÓÑÔÞ AEÑÎÉÐÞ ÕÂÍÉÇ ÓÇÛÂÕßÔâ ØÑÓÑÛÑ, ÐÑ ÃÇÊ ÒÓÑ-âÄÎÇÐËâ ËÊÎËÛÐÇÌ ÒÑÔÒÇÛÐÑÔÕË.•ÂÓÂÍÕÇÓÐÞÌ ÒÓËÏÇÓ.£ 1957 Å. ¯ª ¶ª-2 ÃÞÎ ÒÇÓÇËÏÇÐÑÄÂÐ Ä ¯ªªÁ ¶. £ ÔÄâÊË Ô àÕËÏ ÒÑ ËÐËÙËÂÕËÄÇ ÒÂÓÕËÌÐÑÅÑ ÃáÓÑ (ÚÎÇÐÑÏ ÍÑÕÑÓÑÅÑ ÃÞÎ ³.¯.£ÇÓÐÑÄ) ³.¯.£ÇÓÐÑÄÞÏ Ë ÑAEÐËÏ ËÊ ÂÄÕÑÓÑÄ ÐÂÔÕÑâÜÇÌ ÔÕÂÕßË (¦.¡.²ÑÏÂÐÑÄÔÍËÏ) ÃÞÎ ÒÑAEÅÑÕÑÄÎÇÐ ÒÓÑÇÍÕ ÐÑÄÑÅÑ ÒÑÎÑÉÇÐËâ Ñà ËÐÔÕËÕÖÕÇ, ÑAEÑÃÓÇÐÐÞÌ áÓËAEËÚÇÔÍËÏ ÑÕAEÇÎÑÏ ®¤µ

The process of energy transfer to the emission centers is studied in ZnWO4 and ZnWO4:Mo single crystals in the temperature range 10–300K. A numerical simulation describing the process is presented; the temperature dependence of energy transfer efficiency to the intrinsic emission centers in ZnWO4 is shown to be defined by the modification of Onsager sphere radius. A competitive role of radiative relaxation channel related to the impurity of molybdenum is studied in ZnWO4:Mo. It is shown that below 60K the energy transfer to the MoO6 emission centers by free charge carriers terminates due to the self-trapping of holes at WO6 complexes.

Luminescent properties of magnesium tungstate were investigated. Two samples of MgWO4 single crystals grown by different methods were studied. Only intrinsic luminescence attributed to exciton emission was detected for the both samples and. It was shown that the temperature dependence of the low-energy edge in the excitation spectra obeys Urbach rule. Steepness coefficient that was deduced from this dependence indicates self-trapping of excitons in MgWO4. The absence of cation d states in the valence band is a distinctive feature of MgWO4 that is shown to be manifested in the luminescence excitation spectra.

The luminescence, reflection, and luminescence excitation spectra of two-component Ca1 − x Sr x F2:Ce3+ (0.05 mol %) (x = 0.14, 0.25, 0.4, 0.6, and 0.75) have been studied at room temperature and T = 8 K. It is shown that the luminescence bands (upon 130-eV photon excitation) in the range of 200 to 400 nm are attributed to singlet and triplet self-trapped exciton luminescence and to 5d-4f transitions in Ce3+.

The processes of the excitation energy transfer to the emission centers have been investigated for calcium tungstate crystals taking into account features of the electronic structure of valence band and conduction band. The calculations of the electronic structure of host lattice CaWO4 were performed in the framework of density functional theory. The underestimation of the bandgap value in the calculations has been corrected according to the experimental data. Luminescence of two samples grown using Czochralski (cz) and hydrothermal (ht) techniques were studied. Intrinsic emission band related to excitons, self-trapped on WO4 complexes has been observed for the both samples while the additional low-energy emission band related to the defects of crystal structure has been observed only for (ht) sample indicating the enhanced concentration of the defects in the sample. It was shown that the features of the conduction band electronic structure are reproduced in the excitation spectrum of intrinsic luminescence only for the (ht) sample while for (cz) sample the correlation is absent. The enhanced role of the competitive channels in the process of excitation energy transfer to intrinsic emission centers in (ht) sample is responsible for the observed difference.

Electron thermalization and electron-hole recombination in scintillating crystals is simulated with and without account for Coulomb field created by a hole using both analytical estimations and Monte-Carlo approach. The Monte-Carlo simulation is performed both for crystals with one and two branches of longitudinal optical phonons to check the role of additional branches of these phonons. The results of numerical simulation show that the account for Coulomb field at all stages of the thermalization and capture significantly increases the probability of the geminate electron-hole binding in case of high values of optical phonon energies.

The influence of fluorine doping on the luminescent properties of lead tungstate, PbWO4, a scintillating material used in high-energy physics, was studied. Two series of crystals that were grown by the Czochralski method in two different laboratories were investigated. It was shown that the luminescent properties of the fluorine-doped samples were similar although those of the undoped PbWO4 samples from the different series differed significantly. It was concluded that this was associated with the formation of WO3F complexes in the fluorine-doped PbWO4 crystals.