bluuebunny/crossref_metadata_2025 huggingface dataset:
Specific peptides identified by mass spectrometry in placental tissue from pregnancies complicated by early onset preeclampsia attained by laser capture dissection
Authors: de Groot Christianne J. M. , Güzel Coşkun , Steegers‐Theunissen Régine P. M. , de Maat M. , Derkx Pieter , Roes Eva‐Maria , Heeren Ron M. A. , Luider Theo M. , Steegers Eric A. P.
Published: March 2007

Preeclampsia is a common pregnancy‐specific syndrome that is diagnosed by the appearance of both increased blood pressure and proteinuria. Preeclampsia is associated with significant fetal and maternal morbidity and mortality. Although the etiology of preeclampsia is unknown, it is evident that abnormal placentation and trophoblast metabolism plays an important role. We therefore analyzed, identified, and verified specific proteins of villous trophoblast and villous stroma in small numbers of microdissected cells (approximately 125 cells) from seven placentas of women with pregnancies complicated by preeclampsia (cases) and seven uncomplicated pregnancies (controls). Tryptic peptide profiling by MALDI‐TOF MS was used for comparison and identification of significantly expressed peptides. The data were analyzed by ClinProTools (Bruker Daltonics) and by principal component analysis. Subsequently, a subset of placental tissues were homogenized and separated on a NanoLC system to obtain sequencing information (MS/MS spectra).

We identified specific peptide patterns in the different cell types: villous stroma and trophoblast cells and differences in these cells of placentas from women with pregnancies complicated by early compared to late onset preeclampsia (<34 and >34 wk gestation, respectively) and controls. Principal component analysis revealed significant differences between the groups. The comparison with placental tissue after preterm delivery with unknown cause revealed that placental peptide patterns in early onset preeclampsia could not be explained by preterm delivery per se. Subsequently, specific, discriminating proteins for early onset preeclampsia compared to controls were identified including calcyclin, surfeit locus protein, and choriomammotropin A precursor. The expression of calcyclin was verified in early onset preeclamptic placental sections by immunohistochemistry. These data suggest that in early onset preeclampsia trophoblastic choriomammotropin regulation is abnormal, possibly through abnormal calcyclin expression and regulation.
Photochemical reactions of small mixed alkali‐metal particles in KCl
Authors: Okada T.
Published: March 2007

When the additively colored KCl crystals containing small amounts of Na+ ions are annealed at 370 K, there appears the absorption band attributable to the mixed small colloidal‐particles consisting of K°‐ and Na°‐atoms. We have also found that the thermal annealing of KCl crystals including these mixed K°‐ and Na°‐colloidal particles results in the production of both the K° metal particles and the F centres situating at the normal sites. The optical bleaching of the F centres in the crystals including the colloidal particles is found to be led to produce the isolated FA and M centres. The consideration is also given on the destruction process of the mixed colloidal particles. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence of YAB:Er single crystal
Authors: Földvári I. , Beregi E. , Solarz P. , Dominiak‐Dzik G. , Ryba‐Romanowski W. , Watterich A.
Published: March 2007

Luminescence spectra of YAB:Er crystals were studied in the ultraviolet‐visible region and in the 10–300 K temperature range. The dominant Er3+‐emission belonged to the 4S3/2 → 4I15/2 transition (18000–18500 cm–1). Its Stark components were assigned and found to be consistent with those derived from the absorption spectra. The lifetime of the luminescence was determined as a function of temperature and Er‐concentration, and the decay kinetics was analyzed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computer modelling of intrinsic and substitutional defects in LiNbO3
Authors: Araujo R. M. , Lengyel K. , Jackson R. A. , Valerio M. E. G. , Kovács L.
Published: March 2007

Lithium niobate is a material with many important technological applications due to its diverse physical properties. Using a recently derived interatomic potential, intrinsic defect energies have been calculated leading to conclusions about the defect properties of the material that are compared with experimental conclusions. The incorporation of dopant ions into the structure is also considered, and solution energies are calculated, which enable predictions to be made about which ions are most easily added, and which solution energy schemes are favoured energetically. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescent spectroscopy of lead tungstate crystals doped with europium ions
Authors: Chukova O. , Nedilko S. , Scherbatskyi V.
Published: March 2007

Spectral‐luminescent properties of the lead tungstate crystals doped with the Eu3+ ions were investigated in a wide temperature range at different excitation and registration wave lengths. The spectra consist of both weak wide nonstructural bands of the matrix emission and narrow spectral lines caused by inner f‐f electron transitions in the impurity Eu3+ ions. The analysis and interpretation of spectral lines observed in excitation and luminescence spectra have shown formation of at least two different types of luminescent centers on the basis of the Eu3+ ions in the PbWO4 crystals. These two types of centers are considered as caused by arrangement of the impurity Eu3+ ions in Pb sites as well as in W sites of the host matrix. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison between models of insulator and semiconductor thin films islanding
Authors: Lallet François , Dauger Alain , Olivi‐Tran Nathalie
Published: March 2007

The synthesis of self‐organized quantum dots (QD's) can be achieved through bottom up layer by layer deposition processes as chemical vapor deposition (CVD) or physical vapor deposition (PVD). However, QD's may also be synthesized via sol‐gel route, which involves a spontaneous evolution from thin films to discrete QD's without further deposition. The aim of the paper is to discuss and compare the physical phenomena involved in QD's formation which initiate from thin film surface roughening between PVDCVD and sol‐gel synthesis approaches. We propose two simple physical models which are relevant to explain the fundamental differences between those methods. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge evolution of F2 centers being in different spin states
Authors: Lisitsyna L.
Published: March 2007

Time‐resolved pulse spectrometry methods have been used to study the processes of formation and destruction of F2, F2+, F2– color centers in the time range from 10 ns to 0.1s after irradiation by the electron nanosecond pulse in LiF crystals. It has been found that the direction charge evolution of F2 center under radiation depends on the spin state it is in. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanism of radiation‐induced defects in SiO2: The role of hydrogen
Authors: Salh Roushdey , Fitting H.‐J.
Published: March 2007

Hydrogen related defects in anhydrous “dry”, hydrated “wet” and hydrogen implanted amorphous silicon dioxide (a ‐SiO2) layers are investigated using cathodoluminescence (CL) technique in a wave length range 200–800 nm at specimen temperatures between room and liquid nitrogen temperature. Particular defect centers have been identified including the non‐bridging oxygen hole center (NBOHC) associated with the red luminescence at 650 nm (1.9 eV) and the oxygen deficient centers (ODCs) with the blue (460 nm; 2.7 eV) and UV band (290 nm; 4.3 eV). An additional luminescence band Y in the green‐yellow region has been clearly detected in hydrogen‐implanted as well as in oxygen‐deficient samples. The red luminescence shows quite different CL dose behavior in wet and hydrogen‐treated samples due to dissociation and re‐association of mobile hydrogen and oxygen from and to the NBOHC. The yellow luminescence at 580 nm (2.1 eV) is discussed in terms of radiolytic water dissociation as well as of ODC's in form of small silicon aggregates in the silica matrix. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cathodoluminescence from mixed KTaO3‐KNbO3 crystals
Authors: Kibar R. , Nunn P. J. T. , Townsend P. D. , Wang Y. , Boatner L. A.
Published: March 2007

Cathodoluminescence spectra are shown for a sequence of mixed crystals of KTaO3:KNbO3. The luminescence emission bands are broadly similar across the spectrum from 250 to 850 nm, although their relative strengths are sensitive to composition and temperature. A UV band near 330 nm is only well resolved in some compositions and a broad line near 700 nm may arise from Cr ions. The presence of low temperature phase transitions within the crystals is evidenced by intensity steps and spectral changes of the cathodoluminescence. Hysteresis is seen, as are domain effects and electric field shifts of the transition temperatures. The cathodoluminescence of the surface material reveals more transitions than are reported from earlier bulk studies. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Orientation dependence of the ion beam and cathodoluminescence of albite
Authors: Garcia‐Guinea J. , Finch A. , Can N. , Hole D. , Townsend P.
Published: March 2007

Ion beam induced luminescence and cathodoluminescence of albite produce unexpected differences between (010) and (001) aligned samples. The emission spectra are modified by temperature and different components change in their relative intensity as a result of excitation by different ion beams of H+, H2+ and He+. A consideration of processes which can induce the orientation dependence and the role of excitation density that influences the component features are both discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defects induced in bioglass by gamma radiation for dosimetric purposes
Authors: Da Costa Z. M. , Melo Adeilson P. , Giehl J. M. , Ludwig V. , Pontuschka W. M. , Caldas Linda V. E.
Published: March 2007

Some dosimetric properties of the glass system 50P2O5·30‐40CaO·20‐10Na2O mol% were studied applying the thermoluminescence technique. The glass samples were powdered, and were pressed with Teflon™ in the proportion 1:2 to produce pellets. The glow curves of the pellets presented three peaks at 130 °C, 215 °C and 270 °C, respectively. The TL response reproducibility presented a maximum coefficient of variation lower than 10%. The calibration curve is linear between 1.0 Gy and 1 kGy. Minimum detection limits were also determined. The gamma radiation dose response and the thermal stability of the materials were studied with the purpose to establish the best conditions of the present bioglass system for use in gamma ray TL dosimetry. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical spectra of Tm3+‐doped YAl3(BO3)4 single crystals
Authors: Cavalli E. , Jaque D. , Leonyuk N. I. , Speghini A. , Bettinelli M.
Published: March 2007

Flux grown YAl3(BO3)4 (YAB) crystals doped with Tm3+ have been characterised by optical spectroscopy techniques. The absorption and emission spectra in the UV‐VIS‐NIR region have been measured at 10 and 298 K. The visible emission decay profiles have been measured at room temperature. The low temperature spectra have been used to obtain the energy level scheme of the optically active ion in YAB. The Judd‐Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra in order to evaluate the intensity parameters, the branching ratios and the radiative lifetimes of the emitting states. These have been compared with the experimental values. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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

LiNbO3: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

Thermoluminescence (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

It 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

Thermoluminescence (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

The 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

Time‐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

Transparent 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

This 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

In 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

Phosphorescence 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

In 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

Al 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

Swift 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

In 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

Needle 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

Raman 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

We 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

We 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

In 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

Permanent 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

The 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

We 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

The 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

Mineral 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

Excitation 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

The 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)
Ionic and electronic defects in a‐BaTiO3 thin films studied by transient and steady state conductivity measurements
Authors: El Kamel F. , Gonon P. , Yangui B. , Jomni F.
Published: March 2007

Conduction mechanisms in BaTiO3 films deposited at low temperatures on Cu‐electrodes have been investigated in transient and steady regimes as a function of temperatures and electric field. This work aims to identify possible defects which govern the leakage current. Electrical measurements reveal that Space Charge Limited Current (SCLC) constitutes the main leakage mechanism in both the transient and the steady regimes. Based on the theory of SCLC, two types of defects can be detected. At higher temperatures, oxygen vacancies constitute the main defects which migrate across the film to generate an ionic leakage current. Diffusion of these defects is thermally activated with an activation energy around 1 eV. Moreover, at lower temperatures the J ‐E measurements reveals the presence of a discrete set of shallow traps at 0.45 eV below the conduction band with an effective density of 4 × 1022 m–3. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron‐phonon interaction in Er and Dy doped YAl3(BO3)4 single crystals
Authors: Mazzera M. , Baraldi A. , Capelletti R. , Beregi E. , Földvári I.
Published: March 2007

In the present work high resolution Fourier Transform spectroscopy is applied to monitor the electron‐phonon (e–‐ph) interaction in YAB single crystals doped with trivalent Er and Dy ions. The electron‐phonon coupling is analysed by monitoring the shape, width, and position of the zero‐phonon lines induced by Er3+. The shift and broadening with temperature increasing are discussed in the framework of the two‐phonon Raman scattering. The e–‐ph interaction is revealed even by the presence, in the absorption spectra of Er and Dy doped YAB crystals, of new weak lines attributed to vibronic transitions. The energy separations between the vibronic and the ZP lines are compared with IR‐active modes measured on YAB crystals. Boron isotopic effects are also put in evidence. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High resolution absorption spectroscopy on rare earth doped insulating materials: BaY2F8 and YAl3(BO3)4 single crystals and sol‐gel silica glasses
Authors: Baraldi A. , Capelletti R. , Magnani N. , Mazzera M.
Published: March 2007

The electronic energy transitions occurring in rare earth (RE) ions within the intraconfigurational 4f shell give rise at low temperature to very narrow absorption lines. Even if the shielded 4f shells are weakly coupled with the surrounding, the RE electronic configuration represents a very sensitive probe for the crystal field at the impurity site. Temperature dependent high‐resolution absorption measurements can then provide a deep insight into the local crystal field and into the ion interaction with the host lattice.

Examples of high resolution Fourier transform spectroscopy measurements performed both on crystalline materials (namely fluoride and borate single crystals) and on sol‐gel silica glasses containing nanocrystals are provided and discussed. Correlated analysis based on experimental data and crystal‐field calculations is presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect structure behaviour in metal halides
Authors: Levy Mark R. , Patel Ankoor , Stanek Christopher R. , McClellan Ken , Grimes Robin W.
Published: March 2007

Defects in halide materials have been investigated using atomistic scale computer simulation. These defects are important in controlling a number of key materials properties. Rare‐earth halides (REX3 with X= F, Cl, Br, I) are currently being considered as scintillator hosts. Here we begin by investigating the fluorides (REF3). These materials undergo an experimentally observed structural change as a function of RE cation radius. We have reproduced this structural variation with an atomistic model. In order to optimise scintillator properties, the intrinsic defect mechanisms need to be assessed as such defects act as performance limiting trap sites. The predictions made are interpreted as a function of the host cation radius in order to reveal structural trends. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High resolution FT absorption study of holmium doped yttrium aluminum borate single crystals
Authors: Baraldi A. , Földvári I. , Capelletti R. , Magnani N. , Mazzera M. , Beregi E.
Published: March 2007

High resolution FT spectroscopy has been applied to investigate a YAB: Ho3+ (1 mol%) single crystal, grown by the top‐seeded flux method, in the wave number 4000–25000 cm–1 and temperature 9–300 K ranges, respectively. The complex Ho3+ (4f10) non‐Kramers ion transitions from the ground 5I8 to the excited 5I7, 5I6, 5I5, 5I4, 5F5, 5S2, 5F4, 5F3, 5F2, 3K8, 5F1 + 5G6, and 5G5 manifolds were analyzed. The low‐temperature high resolution spectra of the investigated manifolds show for many electronic transitions hyperfine structures related to the Ho3+ nuclear magnetic moment. The experimental data are fitted by a single ion Hamiltonian and the crystal field parameters are obtained. The results are compared with those previously published for other rare earths in the same matrix. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of structural evolution in Ce‐ and Nd‐doped aluminoborosilicate glasses under β‐irradiation
Authors: Malchukova E. , Boizot B. , Petite G. , Ghaleb D.
Published: March 2007

The structural changes in aluminoborosilicate glasses under β‐irradiation as a function of rare earth oxide content and the dose have been studied using Electron Paramagnetic Resonance (EPR) and luminescence spectroscopies. The EPR measurements at helium temperature (4 K) showed that β‐irradiation affects valence state of cerium ions. According to concentration and dose dependences, the line with g ∼ 2.89 can be attributed to paramagnetic Ce3+ ions resulting from Ce4+ reduction under irradiation. The effect of CeO2 content leads to the modifications of the EPR signal of defects at helium and the change in the relative proportion of electron and hole defects with the increase of the cerium doping level at room temperature. We observed also a decrease of the defect concentration as a function of the Nd doping into these glass compositions but by two orders less than for Ce‐doped samples. Exposure to irradiation induced the appearance of a non‐resolved EPR band in the region of defects. We can assume that possible dipolar interaction between Nd3+ ion and hole can result in not typical EPR resonance shape of paramagnetic defects at g ∼ 2. Moreover, estimation of the ratio between splitted components of the 4F3/2 – 4I9/2 transition depending on the irradiation dose showed that dose increase leads to increase of this ratio suggesting that the nearest environment of Nd ions is expected to be changed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New aspects of light‐induced charge transport in potassium tantalate crystals doped by copper and iron
Authors: Badalyan A. G. , Azzoni C. B. , Galinetto P. , Mozzati M. C. , Jastrabik L. , Rosa J. , Hrabovsky M. , Syrnikov P. P. , Trepakov V. A.
Published: March 2007

The light‐induced charge transport process in as grown and thermally treated in oxygen atmosphere nominally pure KTaO3 (KTO) single crystals and KTO doped by Cu (KTO:Cu) and Fe (KTO:Fe) were studied by electron paramagnetic resonance (EPR). A sizeable increasing of the EPR signal of Cu2+ centers and reducing for Fe3+ centers was observed under UV illumination (365nm) in the oxidized KTO:Cu and KTO:Fe crystals respectively. This effect is considered as a sequence of the light induced charge exchange between Cu+ and Cu2+, and between Fe3+ and Fe2+ centers. Correlation between temperature dependencies of the EPR signals and photoconductivity was found and discussed too. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase composition and crystallinity of thin lead titanate films
Authors: Sidorkin A. A. , Nesterenko L. P. , Smirnov G. L. , Smirnov A. L. , Ryabtsev S. V.
Published: March 2007

Lead titanate thin films with high and stable ferroelectric properties were obtained by plasma‐enhanced magnetron sputtering of pure metals. Effects of crystallites orientation, a substrate and grain boundaries on macroscopic ferroelectric properties of thin films were discussed. It was shown, that strong mechanical stresses, related to different thermal expansion of the film and the substrate materials, render determining influence on crystallites orientation in the film and lead to formation of mechanically clamped non‐ferroelectric layers in the vicinity of interfaces. The use of Al2O3 as substrate material enables the formation of higher quality PbTiO3 films, as compared to the films on the traditional silicon substrates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relaxation emission of electrons and photons from rare‐gas solids: correlation and competition between TSL and TSEE
Authors: Savchenko E. V. , Khyzhniy I. V. , Gumenchuk G. B. , Ponomaryov A. N. , Bondybey V. E.
Published: March 2007

Correlation studies of thermally stimulated luminescence (TSL) and thermally stimulated exoelectron emission (TSEE) from solid Ar pre‐irradiated with an electron beam are presented. Measurements were performed using different heating modes – step‐wise heating and heating with a constant rate. Influence of pre‐existing defects and dose effect on TSL and TSEE are considered. TSEE active layer is estimated. Correlation between TSL and TSEE phenomena pointing to the common primary process – release of electrons from the same kind of traps, is clearly demonstrated. Competition between TSL and TSEE is discussed. It was found that TSEE predominates at low temperatures and in the range of sublimation. Long time irradiation suppressed the total yield of exoelectrons. The part of chemiluminescent reactions in relaxation cascades is elucidated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photon‐stimulated charge recombination and exoelectron emission from pre‐irradiated solid Ar
Authors: Gumenchuk G. B. , Bludov A. M. , Belov A. G. , Ponomaryov A. N. , Bondybey V. E. , Savchenko E. V.
Published: March 2007

Spatially separated stable charge centers – self‐trapped holes, trapped electrons, dopant ionic centers and radicals were generated in an Ar matrix doped with Xe and N2 by a low energy electron beam. A combination of the cathodoluminescence (CL) with the photon‐stimulated luminescence (PSL) and photon‐stimulated exoelectron emission (PSEE) methods was used to monitor center formation and selected relaxation channels – charge recombination reactions and exoelectron emission. PSEE from pre‐irradiated Ar samples was registered simultaneously with N line emission. Vacuum ultraviolet (VUV) intrinsic and extrinsic recombination luminescence from pre‐irradiated samples has been detected to confirm the suggested relaxation path of the stored energy. An afterglow of the N line can be considered as an internal source of photons which releases electrons from the traps and being a triggering mechanism of relaxation processes: (i) – exoelectron emission, (ii) – radiative recombination of charge species. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Soft X‐ray excitation of luminescence in wide bandgap crystals doped with rare‐earth ions
Authors: Meltchakov E. , Vidal B. , Kamenskikh I. , Vasil'ev A. N. , Belsky A. , Dujardin C. , Nannarone S. , Pedio M. , Giglia A. , Mahne N. , Coreno M. , de Simone M. , Danailov M.
Published: March 2007

Luminescence excitation spectra of wide bandgap oxide crystals were measured in the soft X‐ray range of excitation (300–750 eV) at the BEAR beamline of the electron storage ring Elettra (Trieste). We give a special attention to changes of the light yield in the vicinity of the absorption K‐edge of oxygen. The excitation spectra of two well‐known scintillators YAG‐Yb and LuAP‐Ce (chemical formulae are Y3Al5O12:Yb (15%) and LuAlO5:Ce (0.4%)) reveal a non‐proportional change of the quantum yield and a different response to the jump of absorption coefficient at the 1sO edge for certain emission bands. The analysis of experimental data shows that both the surface loss and interaction effects between secondary electronic excitations (EEs) can influence the energy conversion process in crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oxygen transport mechanisms in REAlO3 scintillators
Authors: Stanek C. R. , Uberuaga B. P. , McClellan K. J. , Levy M. R. , Grimes R. W.
Published: March 2007

The performance of oxide scintillators often suffers from phenomena related to the existence of point defects. Thus, if deleterious defects are removed, it follows that scintillator performance will improve. In the case of REAlO3 perovskites, the oxygen vacancy has been identified as the predominant electron trap site. Previous empirical efforts to minimize the concentration of this particular defect through aliovalent doping have been successful. Here we discuss the results of atomic scale simulations that provide important detail regarding the mechanism by which the oxygen vacancy concentration is reduced. Specifically, we describe the complex mobility of oxygen vacancies and interstitials, which governs the recombination of these defects. The results of these simulations will aid in the synthesis of optimized scintillation materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)