bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of Mg doping on the Raman spectra of LiNbO3 crystals
Authors: Lengyel K. , Kovács L. , Péter Á. , Polgár K. , Corradi G. , Bourson P. 
Published: March 2007

AbstractLiNbO3:Mg crystals doped with 0‐8 mol% Mg with stoichiometric, intermediate and congruent compositions were systematically investigated by Raman spectroscopy in backscattering y(zx)y and y(zz)y geometries. The halfwidths of E(TO3) – E(TO9) and A1(TO1) – A1(TO4) bands, which have a significant composition dependence for undoped LiNbO3 crystals, show only weak Mg‐concentration dependence below the photorefractive threshold. This is a consequence of the counteracting effect of the decreasing amount of Nb ions at Li‐ion sites (NbLi) and increasing amount of Mg ions at Li‐ion sites (MgLi). The halfwidths of these bands, however, increase linearly with growing Mg content for samples above the threshold, irrespective of the Li/Nb ratio. The same effect was observed in the Mg dependence of the position and halfwidth of the two‐phonon band at about 689 – 705 cm–1. The change in the Mg concentration dependence of these parameters at a given Li/Nb ratio determines the same threshold value as that concluded from IR and UV spectroscopic measurements. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High temperature thermoluminescence of BaFCl:Eu2+ X‐ray storage phosphor
Authors: Secu C. E. , Secu M. , Predoi D. 
Published: March 2007

AbstractThermoluminescence (TL) of Eu2+‐doped BaFCl polycrystalline powders X‐ray irradiated at room temperature show several TL peaks at 364 K, 408 K, 470 K, 524 K and 646 K. Thermally activated recombination processes responsible for TL have been studied using complementary techniques as TL and its bleaching, diffuse reflectance, X‐ray excited luminescence (XL) and photostimulated luminescence (PSL). Experimental results indicate that F(Cl–) centres are the dominant electron trap centres, the Eu2+‐trapped hole aggregate centres playing the role of recombination centres. The 470 K and 646 K TSL glow peaks are assigned to the recombination inside the triple aggregates (Eu2+ ‐ hole centre ‐ F(Cl–) centre). The remaining 408 K and 524 K TL peaks are tentatively assigned to recombination between F centres and double aggregates (Eu2+ ‐ hole centre). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect characterization methodology in sintered functional spinels with PALS technique
Authors: Balitska V. , Filipecki J. , Ingram A. , Shpotyuk O. 
Published: March 2007

AbstractIt is shown that extended free‐volume defects in sintered functional spinels can be well characterized with positron annihilation lifetime spectroscopy, provided obtained data are treated in terms of unified multi‐channel positron annihilation model involving both positron trapping and ortho‐positronium decay modes. Crystallographical specificity of spinel structure reflects in the shortest lifetime component, while the middle component corresponds to vacancy‐like defects near grain boundaries. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoluminescence and optically stimulated luminescence of gamma‐irradiated mineral zircon
Authors: Secu M. , Vainshtein D. , Turkin A. A. , den Hartog H. W. 
Published: March 2007

AbstractThermoluminescence (TL) manifested by gamma‐irradiated mineral zircon has shown a strong TL peak at about 165 °C which is due to recombination of electrons and Dy3+ related shallow hole traps. After they have been removed by a short preheat we have observed two TL peaks at 300‐320 °C and ≈420 °C, which are mainly due to recombination of electrons and Tb3+ related hole traps centres yielding its characteristic luminescence. The experimental results indicate that optically stimulated luminescence (OSL) is due to luminescent emission of Tb3+ ions and [SiO4]4– groups. The deep traps related to the 420 °C TL peak contribute to the Tb3+ related OSL. The deep traps related to the 300‐320 °C TL peak contribute to OSL associated with the luminescent emission of [SiO4]4– groups. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of γ‐irradiation on the optical properties of a‐Ag7.5 (Sb0.3Ge0.1Se0.6)92.5 thin film
Authors: Salem A. M. , H.Moustafa S. , Marzouk S. Y. 
Published: March 2007

AbstractThe amorphous behaviour of Ag7.5(Sb0.3Ge0.1Se0.6)92.5 chalcogenide thin film deposited at room temperature on glass substrates by thermal evaporation process at vacuum pressure ∼10–3 Pa was examined using X‐ray and electron diffraction techniques. The elemental chemical composition of thin film deposited on carbon stub was investigated via energy dispersive spectroscopy. The optical transmission and reflection spectra of as‐deposited films and those exposed to different γ‐doses were recorded at room temperature within the wavelength range 600‐2500 nm. The dispersion of the refractive index for such films can be described in terms of the single‐oscillator Wemple‐DiDomenico model. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tunneling recombination processes in PbWO4 crystals
Authors: Fabeni P. , Kiisk V. , Krasnikov A. , Nikl M. , Pazzi G. P. , Sildos I. , Zazubovich S. 
Published: March 2007

AbstractTime‐resolved emission and excitation spectra and luminescence decay kinetics were studied at 160‐300 K for undoped and Mo‐doped PbWO4 crystals under XeCl (4.02 eV), N2 (3.67 eV) and KrF (5.0 eV) pulsed excimer laser excitation. The G(II) emission was found to be responsible for the slow (µs‐ms) luminescence decay. Under excitation or after irradiation in the exciton region (Eexc = 4.02 eV), this emission accompanies the monomolecular tunneling recombination in genetic pairs of electron and hole centers produced at the photo‐thermally stimulated decay of localized excitons, which occurs without release of free charge carriers. Under excitation or after irradiation in the host lattice (Eexc = 5.0 eV) and defect‐related (Eexc = 3.67 eV) regions, the bimolecular tunneling recombination takes place in chaotic pairs of the electron and hole centers created at the trapping of optically released free charge carriers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical and optical properties of undoped and In‐doped ZnO thin films
Authors: Caglar Mujdat , Caglar Yasemin , Ilican Saliha 
Published: March 2007

AbstractTransparent conducting undoped and indium‐doped zinc oxide (ZnO) thin films have been deposited by the spray pyrolysis method at 350 °C substrate temperature. X‐ray diffraction spectra of the films have shown that the films are polycrystalline and hexagonal wurtzite in structure. The average optical transmittance of 1% indium‐doped ZnO thin films was over 84% in the visible range. The direct band gap value of the undoped ZnO film was calculated. Electrical conductivity measurement of Ag‐ZnO:In‐Ag structures have been carried out using the two‐probe method in dark, in the range of temperature from 90 to 320 K. The conductivity of undoped and indium‐doped ZnO films increases with increase in temperature. The incorporation of indium in the ZnO film enhanced the conductivity. The conductivity of 1 at.% In‐doped film is higher than undoped ZnO at room temperature. The activation energies Ea values in the range of 90‐320 K temperatures were also determined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of pure and Cr3+ doped BGO ceramic scintillators
Authors: de Mello A. C. S. , Santana G. C. , Jackson R. A. , Macedo Z. S. , Moreira S. G. C. , Valerio M. E. G. 
Published: March 2007

AbstractThis paper reports the production and characterisation of BGO scintillators doped with Cr3+. Single phase Bi4Ge3O12 in pure state and containing up to 1% of the Cr3+ was produced via a solid state route and its luminescent properties were investigated (absorption and emission spectra and radioluminescence). When excited at 200‐230 nm, pure BGO ceramics exhibit a wide photoluminescent band emission centred at 500 nm, assigned to Bi3+ internal transitions. For the doped samples under the same excitation, this wide band was superposed by the emission peaks of the dopant. Computer modelling was employed to help to understand the Cr3+ ‐ doping process in the BGO matrix. The incorporation of the Cr3+ dopant was modelled considering substitution at either Bi3+ or Ge4+ sites. A range of possible charge compensation schemes were devised and the corresponding reactions were used to calculate the energetically optimal defect. The predicted symmetry of the Cr3+ dopant was used to understand the optical properties of the material. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transition dipole interaction of pair SH– ions in KCl
Authors: Afanasiev Alexander D. , Kuznetsov Andrey V. 
Published: March 2007

AbstractIn this work all vibrational transitions up to the second overtone of pair SH– ions in KCl were calculated. The interaction of the identical molecules, which are characterized by “exact” resonance (pairs n SH––n SH, n is a mass number) were researched. The “inexact” interaction (within pairs n SH––m SH–, m ≠ n) was also considered. In both cases the problem was to find wavenumbers and selection rules of vibrational bands from experimental data for single SH– ions in KCl. It was supposed that the dipole moment function is a linear function of the vibrational coordinate. Morse potential function was used as a model of internuclear interaction within SH– ions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phosphorescence of SiO2 optical fibres doped with Ce3+ ions
Authors: Veronese I. , Fasoli M. , Martini M. , Moretti F. , Vedda A. , Loi G. , Mones E. 
Published: March 2007

AbstractPhosphorescence emitted by a new dosimetric system based on a SiO2 optical fibre doped with Ce3+ ions was investigated. The defects in the matrix that, acting as electron traps, originate the phosphorescence signal were studied by means of thermally stimulated luminescence in the temperature interval 313‐533 K. A continuous trap distribution with activation energies extending from 0.8 to 1.5 eV was observed. On the basis of these findings, the temperature dependence of the shape of isothermal phosphorescence decay was analysed and the corresponding spectrum was compared with that of radioluminescence. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principles modelling of defects in advanced nuclear fuels
Authors: Kotomin E. A. , Mastrikov Yu. A. , Zhukovskii Yu. F. , Van Uffelen P. , Rondinella V. V. 
Published: March 2007

AbstractIn this paper we present and discuss the results of first first‐principle modelling of point defects in nitride nuclear fuels. Calculations have been performed using the VASP computer code combined with supercells containing up to 250 atoms. The effective atomic charges, the electronic density redistribution, atomic displacements around U and N vacancies and their formation energies are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanostructured metal/oxide coatings
Authors: Muktepavela F. , Bakradze G. , Stolyarova S. 
Published: March 2007

AbstractAl based nanocomposite coatings on Cu and glass substrates were obtained in the conditions of severe shear stresses by deformation scheme similar to that of friction. Structure, composition and micromechanical properties were investigated using AFM, XRD, SIMS, electron, optical microscopy and precision microindentation techniques. Coatings are characterized by the high microhardness and good adhesion to the substrates. This is determined by the formation of nanostructured Al‐oxide composite stabilized by the presence of oxidized interlayers, which are barriers for the grain growth and intermetallic phase formation. The annealing in vacuum leads to the development of oxygen redistribution processes on interphase boundaries in coatings according to the metal‐oxygen interaction thermodynamics. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Swift heavy ion induced effects in LiF thin films
Authors: Kumar M. , Singh F. , Khan S. A. , Tripathi A. , Gupta A. , Avasthi D. K. , Pandey A. C. 
Published: March 2007

AbstractSwift heavy ions induced effects on optical (color centers), structural and surface (electronic sputtering and morphology) modifications, in nano‐grains LiF thin films were studied by glancing angle X‐ray diffraction, optical absorption, photoluminescence and elastic recoil detection analysis techniques. Our results show that grain size and irradiation temperature play a crucial role in materials modifications as a function of fluence for the selected ion beam parameters. Also for the first time, lamellae formation was observed in LiF thin films after a high fluence irradiation of 5 × 1013 ions/cm2 at liquid nitrogen temperature with 120 MeV Ag ions irradiation under grazing incidence (∼10°). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of ultra‐heavily damaged NaCl
Authors: den Hartog H. W. , Sugonyako A. V. , Vainshtein D. I. , Turkin A. A. , Sulyanov S. N , Kheiker D. M. , Dorovatovskii P. V. 
Published: March 2007

AbstractIn this paper we present the progress made to (i) characterize the defect state of ultra‐heavily damaged rock salt samples with up to more than 20 at% Na colloids, which had been irradiated with 0.5 MeV electrons at 100 ºC up to 104 MGy (1000 GRad), and (ii) understand their physical properties. The explanation of the observations, made by means of a variety of experimental techniques, is not trivial and often the results obtained with different experimental techniques lead to conflicting interpretations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic order in TM‐doped TiO2 single crystals
Authors: Mozzati Maria Cristina , Galinetto Pietro , Azzoni Carlo Bruno , Sangaletti Luigi , Speghini Adolfo , Bettinelli Marco 
Published: March 2007

AbstractNeedle shaped single crystals of TM‐doped rutile TiO2 (TM = Cr, Mn, Fe, Co, Ni, Cu), grown in a sodium tetraborate melt with the flux method, are analysed in their structural and optical properties with a multi‐technique approach. The ferromagnetic behaviour, observed up to room temperature, overlapping the prevailing expected paramagnetism, is investigated by means of static magnetization measurements performed at different temperatures and magnetic fields. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Raman study of the superionic behaviour of CaF2 crystals containing trivalent lanthanide ions
Authors: Mujaji Marjorie , Comins J. D. 
Published: March 2007

AbstractRaman scattering studies of the T2g mode in an undoped CaF2 crystal and in CaF2 crystals separately doped with 10% of Tb3+, Tm3+ and Nd3+ ions as well as 10% to 20% of La3+ ions, in the temperature range 295 K – 1400 K, are presented. The linewidth (FWHM) of the T2g peak is found to increase almost linearly with temperature, up to the transition onset temperature of ∼1025 K for the undoped and between 850 K and 975 K for the 10% doped crystals. Thereafter linewidth increases are steeper in all cases. Further, as the temperature of each sample is raised, the peak position drifts to lower energies. The 15% and 20% La3+‐ doped samples show the same behaviour as for 10% except for slightly lower transition temperature and peak energy. Interstitial F– ions and lattice distortions are responsible for these effects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of Eu3+ and Ce3+ codoping on the relaxation of Er3+ in silica‐hafnia and tellurite glasses
Authors: Mattarelli M. , Montagna M. , Zampedri L. , Bouazaoui M. , Capoen B. , Turrell S. , Ferrari M. , Righini G. C. 
Published: March 2007

AbstractWe studied the spectroscopic properties of Er3+/Ce3+‐codoped tungsten‐tellurite glasses, obtained by melt‐quenching, and of Er3+/Eu3+‐codoped silica‐hafnia waveguides obtained by sol‐gel technique. The study of de‐excitation dynamics of the 4I11/2 and 4I13/2Er3+ states show that Ce3+ and Eu3+ codoping is effective in favoring the population feeding of the 4I13/2Er3+ level. Europium codoping also affects the 4I13/2Er3+ radiative efficiency. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural inhomogeneity of Ge‐doped amorphous SiO2 probed by photoluminescence lifetime measurements under synchrotron radiation
Authors: Agnello S. , Buscarino G. , Cannas M. , Messina F. , Grandi S. , Magistris A. 
Published: March 2007

AbstractWe report a study of the photoluminescence (PL) time decay of the B‐type center, characterized by an optical absorption band peaked at ∼5.2 eV and two related PL bands peaked at ∼3.2 eV and ∼4.3 eV, in sol‐gel Ge‐doped a‐SiO2 under excitation by synchrotron radiation. Measurements were carried out by excitation in UV and in vacuum‐UV (VUV), and were performed in the temperature range from 8 K up to 300 K in order to isolate the effects of the intersystem‐crossing process, proposed to link the two emission bands of the center. Repeating the time decay measurement at several emission energies falling inside the 4.3 eV band, we have observed a variation of the PL decay lifetime with spectral position. The estimated lifetime decreases by more than 25% on increasing emission energy both at high and at low T. The results are interpreted as a fingerprint of the inhomogeneity of the centers and suggest that this method is a direct tool to probe the environment effects on the optical properties of point defects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
TL, ESR and reflectance in natural diopside crystal
Authors: Cano N. F. , Watanabe S. , Mittani J. C. R. , Ayta W. E. F. , Blak A. R. 
Published: March 2007

AbstractIn this paper, results on thermoluminescence (TL) as well as electron spin resonance (ESR) and reflectance of Brazilian diopside samples are presented. The behaviour of the TL centres, ESR signal and reflectance bands under irradiation and heat treatments are examined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Permanent bleaching of F2 color centers in lithium fluoride under UV light illumination
Authors: Vincenti M. A. , Kalinowski H. J. , Montereali R. M. 
Published: March 2007

AbstractPermanent bleaching of F and F2 color centers in gamma irradiated lithium fluoride crystals has been obtained under low power, CW laser illumination at 244 nm. Optical absorption and photoluminescence measurements reveal a selective change in the concentrations of these kinds of electronic defects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometry and ordering of defects in non‐stoichiometric rutile
Authors: Koudriachova M. 
Published: March 2007

AbstractThe geometry of point defects in TiO2–x rutile has been investigated using periodic density functional calculations. A reconstruction of the vacancy site with a neighbouring Ti4+‐ion displaced to an interstitial site was predicted to be thermodynamically favourable. A similar reconstruction of an interstitial site does not lead to a lower energy. Energies of various ordered patterns of the defects were compared, including that in the shear planes. A particular favourable ordering was found in the (132) shear planes for O‐vacancies and in the (121) shear planes for Ti‐interstitials. Comparison of the defect formation energies revealed that in highly non‐stoichiometric rutile Ti‐interstitials are more stable than O‐vacancies. However, the difference between the formation energies decreases rapidly as rutile becomes more stoichiometric, indicating that at a very low defect concentrations O‐vacancies may be the majority type defect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical absorption induced by UV laser radiation in Ge‐doped amorphous silica probed by in situ spectroscopy
Authors: Messina F. , Cannas M. , Boscaino R. , Grandi S. , Mustarelli P. 
Published: March 2007

AbstractWe studied the optical absorption induced by 4.7 eV pulsed laser radiation on Ge‐doped a‐SiO2 synthesized by a sol‐gel technique. The absorption spectra in the ultraviolet spectral range were measured during and after the end of irradiation with an in situ technique, evidencing the growth of an absorption signal whose profile is characterized by two main peaks near 4.5 eV and 5.7 eV and whose shape depends on time. Electron spin resonance measurements performed ex situ a few hours after the end of exposure permit to complete the information acquired by optical absorption by detection of the paramagnetic Ge(1) (GeO4)– and Ge‐E' (≡Ge•) centers laser‐induced in the samples. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluoride crystals growth and color center production by high intensity ultra short laser pulses
Authors: Baldochi S. L. , Courrol L. C. , Samad R. E. , Ranieri I. M. , Gomes L. , de Freitas A. Z. , Vieira N. D 
Published: March 2007

AbstractThe production of stable color centers in fluoride crystals (BaLiF3) by ultrashort high intensity laser irradiation was investigated. A comparison between the optical properties of color centers produced in samples grown by different methods was done. We were able to observe absorption bands at 260, 420, 632, 386 and 480 nm attributed to F, F2, F2+, F3 and F3+ centre, as the ones produced on these crystals by electron‐irradiation. The formation of these defects in BaLiF3 is strongly related to the crystal growth conditions. The higher crystalline order favors the formation of larger clusters. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of optically‐stimulated luminescence of zircon
Authors: Turkin A. A. , Vainshtein D. I. , Hartog H. W. den 
Published: March 2007

AbstractMineral zircon, ZrSiO4, belongs to a class of materials that can be used as a chronological tool in geology and archaeology for measurements of the natural radiation dose and the sample age by optical methods. The model of optically stimulated luminescence developed earlier is used to investigate the applicability of the single‐aliquot regenerative‐dose method (SAR) for dating with zircon. Various implementations of the SAR method are considered and practical recommendations are formulated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inter‐ and intraconfigurational luminescence of trivalent rare earth ions doped into strontium fluoride crystals under vacuum ultraviolet excitation
Authors: Ivanovskikh Konstantin , Pustovarov Vladimir , Smirnov Andrey , Shulgin Boris 
Published: March 2007

AbstractExcitation spectra for intra‐ (4fn → 4fn) and interconfigurational (4fn–15d → 4fn) radiative transitions of trivalent rare earth ions doped into SrF2 crystals have been investigated using VUV synchrotron radiation. The intra‐centre and band‐to‐band excitation mechanisms are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A crystal‐field study of erbium oxide and fluoride
Authors: Magnani N. , Baraldi A. , Buffagni E. , Capelletti R. , Mazzera M. , Brovelli S. , Lauria A. 
Published: March 2007

AbstractThe energy levels belonging to the three lowest J multiplets of the Er3+ ion in Er2O3 and ErF3 were determined by means of high‐resolution optical absorption spectroscopy. A crystal‐field analysis of these data by means of Newman's Superposition Model was performed, allowing to determine intrinsic parameters which are quite consistent with other oxides and fluorides and to check the validity of the transferability postulate within these compounds. The possibility to use these data to analyze crystalline nanophases in glasses is briefly discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)