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1

Nuclear orientation of154Eu Fe,166Tm Gd and169Yb Fe and169Yb Gd  

NASA Astrophysics Data System (ADS)

Nuclear orientation measurements at low temperatures have been carried out on radioactive isotopes of154Eu and169Yb in Fe and of166Tm and169Yb in Gd. Gamma-rays from169Yb Gd, obtained by the decay of implanted and melted sample of169Iu Gd, were observed to have smaller anisotropies of opposite signs compared with those from169Yb Fe. This may indicate that for Yb polarized in Gd electric quadrupole interaction is comparable with magnetic dipole one. Mixing ratios of the transitions in154Gd,166Er and169Tm have been made for two levels in166Er. Our analysis showed that the 3- to 3+ beta decay to the 1128 keV level in154Gd has 65(20)% ?j?=0.

Kracíková, T. I.; Davaa, S.; Finger, M.; Pavlov, V. N.; Tsupko-Sitnikov, V. M.

1987-03-01

2

High temperature enthalpies and related thermodynamic functions of the trifluorides of Sc, Ce, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb  

Microsoft Academic Search

The high temperature enthalpies of high purity ScF3, CeF3, SmF3, GdF3 (redetermined), TbF3, DyF3, ErF3, TmF3, and YbF3 were measured from 100 to 1600°C and EuF3 from 100 to 975°C. The thermal data for the other fluorides in the rare earth series were reported earlier from this laboratory. The heat capacity, enthalpies of transition and fusion, and related thermodynamic functions

F. H. Spedding; B. J. Beaudry; D. C. Henderson; J. Moorman

1974-01-01

3

Multifunctional ScF3:Ln3+ (Ln = Tb, Eu, Yb, Er, Tm and Ho) nano/microcrystals: hydrothermal/solvothermal synthesis, electronic structure, magnetism and tunable luminescence properties  

NASA Astrophysics Data System (ADS)

A facile, hydrothermal/solvothermal route has been developed to synthesize a series of multifunctional lanthanide ion (Tb3+, Eu3+, Yb3+, Tm3+, Er3+ and Ho3+)-activated ScF3 nanocrystals. The morphology and size of ScF3 can be tuned in a controlled manner by altering the additives and volume ratios of H2O : EtOH in the initial solution. Under ultraviolet (UV), vacuum ultraviolet (VUV) or low-voltage electron-beam excitation, the as-obtained Tb3+, Eu3+ codoped ScF3 product exhibits multicolor photoluminescence (PL) and cathodoluminescence (CL), and possible luminescence mechanisms are discussed. Moreover, under 980 nm excitation, upconversion (UC) emissions have been achieved in Yb3+-Er3+, Yb3+-Tm3+, and Yb3+-Ho3+ codoped ScF3. Ferromagnetic property of ScF3 is detected due to the nanocrystal defects. The results obtained indicate that the lanthanide ion-doped ScF3 nanocrystals exhibit multicolor UV/VUV PL, CL, and UC luminescence as well as ferromagnetic properties. Thus, they may have potential applications in PL areas, field emission display devices, bioseparation and magnetic resonance imaging.A facile, hydrothermal/solvothermal route has been developed to synthesize a series of multifunctional lanthanide ion (Tb3+, Eu3+, Yb3+, Tm3+, Er3+ and Ho3+)-activated ScF3 nanocrystals. The morphology and size of ScF3 can be tuned in a controlled manner by altering the additives and volume ratios of H2O : EtOH in the initial solution. Under ultraviolet (UV), vacuum ultraviolet (VUV) or low-voltage electron-beam excitation, the as-obtained Tb3+, Eu3+ codoped ScF3 product exhibits multicolor photoluminescence (PL) and cathodoluminescence (CL), and possible luminescence mechanisms are discussed. Moreover, under 980 nm excitation, upconversion (UC) emissions have been achieved in Yb3+-Er3+, Yb3+-Tm3+, and Yb3+-Ho3+ codoped ScF3. Ferromagnetic property of ScF3 is detected due to the nanocrystal defects. The results obtained indicate that the lanthanide ion-doped ScF3 nanocrystals exhibit multicolor UV/VUV PL, CL, and UC luminescence as well as ferromagnetic properties. Thus, they may have potential applications in PL areas, field emission display devices, bioseparation and magnetic resonance imaging. Electronic supplementary information (ESI) available: The UV/VUV/CL spectra of nanocrystal defects in ScF3 and the calculation of electron penetration depths. See DOI: 10.1039/c4nr00512k

Han, Lili; Wang, Yuhua; Guo, Linna; Zhao, Lei; Tao, Ye

2014-05-01

4

Thermal activation, cathodo- and photoluminescence measurements of rare earth doped (Tm, Tb, Dy, Eu, Sm, Yb) amorphous\\/nanocrystalline AlN thin films prepared by reactive rf-sputtering  

Microsoft Academic Search

We present comprehensive cathodo- and photoluminescence measurements from thin amorphous\\/nanocrystalline (a\\/nc-) AlN films doped with rare earths. The (a\\/nc-) AlN films were prepared by reactive rf-sputtering using a high purity (5N) aluminium disk in high purity nitrogen atmosphere (5N, pressure ca. 1.3mbar). The rare earth doping (Tm,Tb,Dy,Eu,Sm,Yb, concentrations were below 1%) was performed by placing respective rare earth metal pieces

R. Weingärtner; O. Erlenbach; A. Winnacker; A. Welte; I. Brauer; H. Mendel; H. P. Strunk; C. T. M. Ribeiro; A. R. Zanatta

2006-01-01

5

Large-scale synthesis of Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres and their photoluminescence properties  

SciTech Connect

Graphical abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. Display Omitted Highlights: ? Lu{sub 2}O{sub 3}:Ln{sup 3+} microspheres were prepared by a precipitation followed by a calcination process. ? Lu{sub 2}O{sub 3}:Eu{sup 3+}/Tb{sup 3+} samples exhibit respective red or green emissions. ? Lu{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}/Tm{sup 3+}/Ho{sup 3+} exhibit emissions of green, blue, yellow-green, respectively. ? These finding may find potential applications in bioanalysis and field emission displays. -- Abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and cathodoluminescence (CL) spectra were employed to characterize the samples. Upon ultraviolet and low-voltage electron beams excitation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+} and Tb{sup 3+}) samples exhibit respective bright red (Eu{sup 3+}, {sup 5}D{sub 0} ? {sup 7}F{sub 2}) and green (Tb{sup 3+}, {sup 5}D{sub 4} ? {sup 7}F{sub 5}) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) exhibit characteristic up-conversion (UC) emissions of green (Er{sup 3+}, {sup 4}S{sub 3/2}, {sup 2}H{sub 11/2} ? {sup 4}I{sub 15/2}), blue (Tm{sup 3+}, {sup 1}G{sub 4} ? {sup 3}H{sub 6}) and yellow-green (Ho{sup 3+}, {sup 5}F{sub 4}, {sup 5}S{sub 2} ? {sup 5}I{sub 8}), respectively. These finding may find potential applications in bioanalysis, optoelectronic and nanoscale devices, field emission displays, and so on.

Gao, Yu, E-mail: gaoy777@126.com [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China)] [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China); Gong, Jian [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Changchun, Jilin 130024 (China)] [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Changchun, Jilin 130024 (China); Fan, Miaomiao [Department of Medical Pharmaceutical, Shenyang Chemical Industry School, Shenyang 110142 (China)] [Department of Medical Pharmaceutical, Shenyang Chemical Industry School, Shenyang 110142 (China); Fang, Qinghong; Wang, Na; Han, Wenchi; Xu, Zhenhe [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China)] [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China)

2012-12-15

6

Multifunctional ScF3:Ln(3+) (Ln = Tb, Eu, Yb, Er, Tm and Ho) nano/microcrystals: hydrothermal/solvothermal synthesis, electronic structure, magnetism and tunable luminescence properties.  

PubMed

A facile, hydrothermal/solvothermal route has been developed to synthesize a series of multifunctional lanthanide ion (Tb(3+), Eu(3+), Yb(3+), Tm(3+), Er(3+) and Ho(3+))-activated ScF3 nanocrystals. The morphology and size of ScF3 can be tuned in a controlled manner by altering the additives and volume ratios of H2O?:?EtOH in the initial solution. Under ultraviolet (UV), vacuum ultraviolet (VUV) or low-voltage electron-beam excitation, the as-obtained Tb(3+), Eu(3+) codoped ScF3 product exhibits multicolor photoluminescence (PL) and cathodoluminescence (CL), and possible luminescence mechanisms are discussed. Moreover, under 980 nm excitation, upconversion (UC) emissions have been achieved in Yb(3+)-Er(3+), Yb(3+)-Tm(3+), and Yb(3+)-Ho(3+) codoped ScF3. Ferromagnetic property of ScF3 is detected due to the nanocrystal defects. The results obtained indicate that the lanthanide ion-doped ScF3 nanocrystals exhibit multicolor UV/VUV PL, CL, and UC luminescence as well as ferromagnetic properties. Thus, they may have potential applications in PL areas, field emission display devices, bioseparation and magnetic resonance imaging. PMID:24759954

Han, Lili; Wang, Yuhua; Guo, Linna; Zhao, Lei; Tao, Ye

2014-06-01

7

Experimental study of the 4fn ? 4fn and 4fn ? 4fn-15d1 transitions of the lanthanide diiodides LnI2 (Ln=Nd, Sm, Eu, Dy, Tm, Yb).  

PubMed

The diffuse reflectance and photoluminescence (PL) spectra of NdI(2), SmI(2), EuI(2), DyI(2), TmI(2) and YbI(2) were measured between 225 and 12 500 nm in order to determine their 4f(n) ? 4f(n-1)5d(1) optical bandgaps. The results were compared with those obtained using an empirical model of the electronic structure of LnI(2). The results can be used to explain the lanthanide valency and crystalline structure changes of other lanthanide diiodides such as PrI(2). PMID:22713248

Rogers, E; Dorenbos, P; de Haas, J T M; van der Kolk, E

2012-07-11

8

Upconversion processes in Yb-sensitized Tm:ZBLAN  

SciTech Connect

A spectroscopic study of 22 rare-earth-ion doped ZBLAN (fluorozirconate) glass was done to study feasibility of sensitizing Tm:ZBLAN with Yb to facilitate development of an efficient, conveniently pumped blue upconversion fiber laser. it was found that, under single-color pumping, 480 nm emission from Tm{sup 3+} was strongest when Yb,Tm:ZBLAN is excited at 975 nm; the strongest blue blue emission was obtained from a glass sample with 2.0 wt% Yb + 0.3 wt% Tm. Also, for weak 975 nm pump intensities, strength of blue upconversion emission can be greatly enhanced by simultaneously pumping at 785 nm. This increased upconversion efficiency is due to reduced number of energy transfer steps needed to populate the Tm{sup 3+} {sup 1}G{sub 4} energy level. Measurements of fluorescence lifetimes vs dopant concentration were also made for Yb{sup 3+}, Tm{sup 3+}, and Pr{sup 3+} transitions in ZBLAN in order to better characterize concentration quenching effects. Energy transfer between Tm{sup 3+} and Pr{sup 3+} in ZBLAN is also described.

Carrig, T.J. [Coherent Technologies, Inc., Lafayette, CO (United States); Cockroft, N.J. [Los Alamos National Lab., NM (United States)

1996-10-01

9

Energy transfer efficiency in YF3 nanocrystals: Quantifying the Yb3+ to Tm3+ infrared dynamics  

NASA Astrophysics Data System (ADS)

In this work, we report on the determination of the infrared Yb3+ --> Tm3+ energy transfer efficiency in YF3:Yb3+/Tm3+ nanocrystals through the study of Yb3+ dynamics. The obtained results are compared to those previously reported in macrocrystals to analyze possible changes related to size reduction. Luminescence lifetimes are much shorter in the nanoparticles than in bulk samples, a behavior that can be related to Yb3+ --> Yb3+ migration and the enhanced surface/volume ratio of the nanoparticles. On the other hand, Yb3+ --> Tm3+ energy transfer macroparameter remains unaltered, demonstrating that spectroscopic intrinsic parameters such as radiative and non-radiative probabilities are not affected by size reduction. Finally, a formula that describes Yb3+ lifetime dependence with Yb3+ and Tm3+ concentration is proposed, considering both the effects produced by migration between Yb3+ ions and energy transfer from Yb3+ to Tm3+ ions.

Quintanilla, Marta; Núñez, Nuria O.; Cantelar, Eugenio; Ocaña, Manuel; Cussó, Fernando

2013-05-01

10

Emission spectroscopy and energy transfer in Tm3+, Tm3+Ho3+, and Tm3+Yb3+ doped tellurite fibers  

Microsoft Academic Search

This paper examines the steady state and time resolved emission spectroscopy of Tm3+ doped and Tm3+-Ho3+, Tm3+-Yb3+ co-doped tellurite fibers for mid-IR fiber laser design which find applications for lidar. These doped fibers show promising properties for compact and tunable laser sources in the visible and mid-IR when pumped at 800 nm, 980 nm and 1480 nm which can be

Billy Richards; Shaoxiong Shen; Animesh Jha

2006-01-01

11

Ion size effect of rare earth on T c, T N and ? n in (R 1-xPr x)Ba 2Cu 3O 7-y systems (R?Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, Sm and Nd)  

NASA Astrophysics Data System (ADS)

A detailed study of the superconductivity, magnetic ordering of Pr ions and the normal transport properties is reported for sintered (R 1-xPr x)Ba 2Cu 3O 7 samples (R?Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, Sm and Nd) with x = 0-1.0. We found that at a constant Pr concentration, x, the superconducting transition temperature T c, the antiferromagnetic ordering temperature T N of Pr ions and the normal state resistivity ? n in (R 1-xPr x)Ba 2Cu 3O 7 systems are R ion-size dependent. Observed results were interpreted in terms of the hybridization between the local states of Pr ion and the conduction band states of the CuO 2 planes.

Guan, Weiyan

1994-12-01

12

Observation of bistable upconversion emission in Tm,Yb codoped yttria nanocrystal  

NASA Astrophysics Data System (ADS)

Nonlinear upconversion emission properties in Tm and Yb codoped yttria nanocrystal have been studied under 973 nm laser excitation. Intrinsic bistability and hysteresis have been observed for the bright blue upconversion luminescence of Tm3+ ions at room temperature. The mechanism of the Tm3+ bistable emission is mainly related to laser-induced local thermal effects which cause the enhancement of sequential multi-photon energy transfer upconversion of Yb3+-Tm3+ pairs.

Li, L.; Li, H.; Zhang, X. L.; Peng, Y. F.; Nie, M.; Jiang, B.; Zhang, X. W.; Li, R. M.

2010-11-01

13

Optical parameters and upconversion fluorescence in Tm3+/Yb3+ codoped tellurite glass  

NASA Astrophysics Data System (ADS)

Tm3+/Yb3+ codoped tellurite glass has been prepared. Density, refractive index, optical absorption, Judd-Ofelt parameters and spontaneous transition probabilities of Tm3+ have been measured and calculated, respectively. Intense blue three-photon upconversion fluorescence and S-band (1470 nm) fluorescence were investigated under the excitation of a 980 nm diode laser at room temperature. Judd-Ofelt parameters, strong blue three-photon upcoversion emission of Tm3+ in glass indicate that Tm3+/Yb3+ codoped tellurite glass is a promising blue color upconversion optical and laser material. In addition, experiment results showed the 980 nm laser was more efficient than 808 nm laser when pumping Tm3+/Yb3+ codoped tellurite glass, Tm3+/Yb3+ codoped tellurite glass also could be a promising material for S-band amplification.

Huang, Q. J.; Wang, Q. P.; Chang, J.; Zhang, X. Y.; Liu, Z. J.; Yu, G. Y.

2010-04-01

14

Multiphoton ultraviolet and visible upconversion luminescence of Tm 3+Yb 3+ co-doped oxyfluoride glass  

NASA Astrophysics Data System (ADS)

The ultraviolet upconversion luminescence of Tm 3+ ions sensitized by Yb 3+ ions in oxyfluoride glass when excited by a 975 nm diode laser was studied in this paper. One typical ultraviolet upconversion luminescence lines positioned at 362.3 nm was found. It can be attributed to the five-photon upconversion luminescence transition of 1D 2 ? 3H 6. Several visible upconversion luminescence lines at 451.1 nm, (477.9 nm, 462.5 nm), 648.7 nm, (680.5 nm, 699.5 nm) and (777.5 nm, 800.7 nm) were found also, which results from the fluorescence transitions of five-photon 1D 2 ? 3F 4, three-photon 1G 4 ? 3H 6, three-photon 1G 4 ? 3F 4, two-photon 3F 3 ? 3H 6 and two-photon 3H 4 ? 3H 6 of Tm 3+ ion, respectively. The theoretical analysis suggests that the upconversion mechanism of the 362.3 nm 1D 2 ? 3H 6 upconversion luminescence is the cross energy transfer of { 3H 4(Tm 3+) ? 3F 4(Tm 3+), 1G 4(Tm 3+) ? 1D 2(Tm 3+)} and { 1G 4(Tm 3+) ? 3F 4(Tm 3+), 3H 4(Tm 3+) ? 1D 2(Tm 3+)} between Tm 3+ ions. In addition, the upconversion luminescence of 1G 4 and 3H 4 state results from the sequential energy transfer { 2F 5/2(Yb 3+) ? 2F 7/2(Yb 3+), 3H 4(Tm 3+) ? 1G 4(Tm 3+)} and { 2F 5/2(Yb 3+) ? 2F 7/2(Yb 3+), 3F 4(Tm 3+) ? 3F 2(Tm 3+)} from Yb 3+ ions to Tm 3+ions, respectively.

Chen, Xiaobo; Wang, Yafei; Song, Zengfu; Sawanobori, N.; Ohtsuka, M.

2007-09-01

15

Enhanced 1.8 ?m emission in Yb3+/Tm3+ co-doped tellurite glass: Effects of Yb3+?Tm3+ energy transfer and back transfer  

NASA Astrophysics Data System (ADS)

The ~1.8 ?m emission characteristics of Tm3+ by a direct excitation and through an energy transfer process upon sensitization with Yb3+ ions in tellurite glass are reported. The spectroscopic properties of Tm3+ ions have been evaluated by applying Judd-Ofelt theory on the measured absorption spectrum. The obtained intensity parameters, ?2=7.155×10-20 cm2, ?4=3.325×10-20 cm2, ?6=1.278×10-20 cm2 are used to estimate the radiative properties of Tm3+ ions in the present glass host. A ~10 fold enhancement in the Tm3+ 1.8 ?m emission observed with 16 fold reduced emission of Yb3+ ions (1008 nm) in co-doped sample on Yb3+ ions excitation illustrates the efficient energy transfer from Yb3+: 2F5/2?Tm3+: 3H5. The energy transfer process assisted by host phonon energy has been discussed by using relevant theoretical models and estimated the energy transfer micro-parameters. Effect of energy back transfer Tm3+?Yb3+ on NIR and upconversion emissions have been discussed. An efficient ~1.8 ?m with comparatively higher emission cross-section 1.115×10-20 cm2 on account of reduced upconversion emissions has been achieved in the present tellurite glass.

Balaji, Sathravada; Biswas, Kaushik; Sontakke, Atul D.; Gupta, Gaurav; Annapurna, Kalyandurg

2014-11-01

16

Tm-Yb-Tm energy transfers and effect of temperature on the fluorescence intensities in oxyfluoride tellurite compounds  

Microsoft Academic Search

Up-conversion processes in PbF2+TeO2+WO3 glass-ceramics doped with Tm3+ and codoped with Tm3+ and Yb3+ ions were investigated under 680 nm excitation. Emission, excitation and time-resolved spectra and decay profiles were measured at temperatures between 12 and 300 K. A strong blue emission centred at 478 nm originating from the 1G4 level of Tm3+ was observed in a doubly doped sample

G. Ozen; J.-P. Denis; M. Genotelle; F. Pelle

1995-01-01

17

Yb3+ sensitized Tm3+ upconversion in tellurite lead oxide glass  

NASA Astrophysics Data System (ADS)

Triply ionized thulium/thulium - ytterbium doped/codoped TeO2-Pb3O4 (TPO) glasses have been fabricated by classical quenching method. The upconversion emission spectra in the Tm3+/Tm3+-Yb3+ doped/codoped glasses upon excitation with a diode laser lasing at ˜980 nm has been studied. Effect of the addition of the Yb3+ on the upconversion emission intensity in the visible and near infrared regions of the Tm3+ doped in TPO glass has been studied and the processes involved explored.

Mohanty, Deepak Kumar; Rai, Vineet Kumar; Dwivedi, Y.

2012-04-01

18

Yb3+ sensitized Tm3+ upconversion in tellurite lead oxide glass.  

PubMed

Triply ionized thulium/thulium--ytterbium doped/codoped TeO2-Pb3O4 (TPO) glasses have been fabricated by classical quenching method. The upconversion emission spectra in the Tm3+/Tm3+-Yb3+ doped/codoped glasses upon excitation with a diode laser lasing at ?980 nm has been studied. Effect of the addition of the Yb3+ on the upconversion emission intensity in the visible and near infrared regions of the Tm3+ doped in TPO glass has been studied and the processes involved explored. PMID:22265952

Mohanty, Deepak Kumar; Rai, Vineet Kumar; Dwivedi, Y

2012-04-01

19

Optical properties, fluorescence mechanisms and energy transfer in Tm 3+, Ho 3+ and Tm 3+ -Ho 3+ doped near-infrared laser glasses, sensitized by Yb 3+  

NASA Astrophysics Data System (ADS)

The optical properties of the rare elements Tm 3+, Ho 3+ and Yb 3+ were systematically investigated in various glasses. The Tm 3+ doped aluminozircofluoride glass shows higher quantum efficiency, longer lifetime and stronger fluorescence intensity than Tm 3+ doped YSGG crystal and other Tm 3+ doped glasses for the 3H4 ? 3H6 transition. Similar quantum efficiency, longer lifetime and stronger fluorescence intensity were also found in Ho 3+ doped aluminozircofluoride glass for the 5I7 ? 5I8 transition. The higher quantum efficiencies of Tm 3+ and Ho 3+ in aluminozircofluoride glass are due to the longer lifetime and the lower phonon energy. The fluorescence mechanisms and energy transfer in the Yb 3+ -Tm 3+ system, Yb 3+ -Ho 3+ system and Yb 3+ - Tm 3+ -Ho 3+ system were studied. The very strong fluorescence intensities in the Yb 3+ -Tm 3+ system for Tm 3+ and the Yb 3+ -Tm 3+ -Ho 3+ system for Ho 3+ which are 1.68 times that of Tm 3+ doped YSGG crystal and 2.25 times that of Tm 3+?Ho 3+ codoped YSGG crystal are attributed to the efficient Yb 3+ ? Tm 3+, Yb 3+ ? Ho 3+ and Tm 3+ ? Ho 3+ energy transfer processes. The fluorescence processes are described by cross relaxations of 2F{5}/{2} ? 3H5 ? 3H4 ? 3H6 ? 2F{7}/{2}and2F{5}/{2} ? 3H5 (or 2F{5}/{2} ? 5I6 ? 3H5) ? 3H4 ? 5I7 ? 5I8 ? 3H6 ? 2F{7}/{2}.

Peng, Bo; Izumitani, Tetsuro

1995-10-01

20

Highly efficient blue up-conversion of Tm 3+ in Nd 3+–Yb 3+–Tm 3+ co-doped ZrF 4-based fluoride glass  

Microsoft Academic Search

Up-conversion luminescence and energy-transfer processes in Nd3+, Yb3+ and Tm3+ co-doped ZrF4-based fluoride glasses have been studied under 800nm light excitation. Blue up-converted emission around 478nm which can be assigned to the Tm3+:1G4?3H6 transition, was strongly observed. Up-conversion luminescence intensity exhibited an YbF3-concentration dependence. Among the Nd3+, Yb3+ and Tm3+, Nd3+ and Tm3+ have ground state absorption bands due to

J Qiu; Y Kawamoto

2001-01-01

21

The performance of density functional theory for LnF (Ln=Nd, Eu, Gd, Yb) and YbH  

Microsoft Academic Search

Different density functional theory (DFT) functionals have been evaluated by studying geometries and bond strengths of YbH, YbF, EuF, GdF, and NdF and compared with accurate CCSD(T) results and, when available, experiment. The agreement between the CCSD(T) results and experiment, when available, is good. The agreement is also good between bond strengths calculated at the DFT level using relativistic effective

Hanne Heiberg; Odd Gropen; Jon K. Laerdahl; Ole Swang; Ulf Wahlgren

2003-01-01

22

Spin-reorientation transitions in Er, Tm and Yb orthoferrites: magnetic and structural properties  

Microsoft Academic Search

Magnetic and structural characteristics of ErFeO3, TmFeO3 and YbFeO3 single crystals were studied over a wide temperature range. Magnetic measurements found that the spin-rotation transitions in all crystals are well described by the earlier proposed theory with no fitting parameters. Additionally, they have shown the absence of the magnetic compensation point in TmFeO3, and a noticeable growth of the c-axis

Ya. B. Bazaliy; L. T. Tsymbal; V. N. Derkachenko; V. I. Kamenev; G. N. Kakazei; F. J. Palomares; P. E. Wigen

2008-01-01

23

Upconversion properties of Er3+, Yb3+ and Tm3+ codoped fluorophosphate glasses.  

PubMed

Er3+, Yb3+ and Tm3+ codoped fluorophosphate glasses emitting blue, green and red upconversion luminescence at 970 nm laser diode excitation were studied. It was shown that Tm3+ behaves as the sensitizer to Er3+ for the green upconversion luminescence through the energy transfer process: Tm3+:3H4+Er3+:4I 15/2-->Er3+:4I 9/2+Tm3+:3H6, and for the red upconversion luminescence through the energy transfer process: Tm3+:3F4+Er3+:4I 11/2-->Tm3+:3H6+Er3+:4F 9/2. Moreover, Er3+ acts as quenching center for the blue upconversion luminescence of Tm3+. The sensitization of Tm3+ to Er3+ depends on the concentration of Yb3+. The intensity of blue, green and red emissions can be changed by adjusting the concentrations of the three kinds of rare earth ions. This research may provide useful information for the development of high color and spatial resolution devices and white light simulation. PMID:17329153

Liao, Meisong; Hu, Lili; Fang, Yongzheng; Zhang, Junjie; Sun, Hongtao; Xu, Shiqing; Zhang, Liyan

2007-11-01

24

Red to blue up-conversion emission of Tm3 + ions in Yb3 + -doped glass ceramic  

Microsoft Academic Search

A detailed study of the spectroscopic properties of PbF2+GeO2+WO3 glass ceramics doped with Tm3+ and codoped with Tm3+ and Yb3+ ions upon 680 nm dye laser light excitation has been made. The absorption, up-conversion emission, excitation, and time-resolved spectra were measured as a function of TmF3 and YbF3 concentrations at room temperature. An enhancement of blue emission centered at 478

Wu Xu; J. P. Denis; G. Özen; A. Kermaoui; F. Pellé; B. Blanzat

1994-01-01

25

Optical properties, fluorescence mechanisms and energy transfer in Tm 3+, Ho 3+ and Tm 3+ Ho 3+ doped near-infrared laser glasses, sensitized by Yb 3+  

Microsoft Academic Search

The optical properties of the rare elements Tm3+, Ho3+ and Yb3+ were systematically investigated in various glasses. The Tm3+ doped aluminozircofluoride glass shows higher quantum efficiency, longer lifetime and stronger fluorescence intensity than Tm3+ doped YSGG crystal and other Tm3+ doped glasses for the 3H4 ? 3H6 transition. Similar quantum efficiency, longer lifetime and stronger fluorescence intensity were also found

B. Peng; Tetsuro Izumitani

1995-01-01

26

Upconversion fluorescence and thermal optical bistability in Gd2O3: 10% Yb3+, 0.5% Tm3+  

Microsoft Academic Search

Through a co-precipitation method Gd(OH)3: 0.5% Tm3+, 10% Yb3+ powder was synthesized. After sintering at different temperatures, the as-prepared Gd(OH)3: 0.5% Tm3+, 10% Yb3+ powder was changed into cubic and monoclinic phase Gd2O3: 0.5% Tm3+, 10% Yb3+ phosphors. Crystalline phases and morphologies of as-prepared powder and phosphors were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM).

Chunyan Cao; Xianmin Zhang; Minglun Chen; Weiping Qin; Jisen Zhang

2010-01-01

27

Upconversion fluorescence and thermal optical bistability in Gd 2O 3: 10% Yb 3+, 0.5% Tm 3+  

Microsoft Academic Search

Through a co-precipitation method Gd(OH)3: 0.5% Tm3+, 10% Yb3+ powder was synthesized. After sintering at different temperatures, the as-prepared Gd(OH)3: 0.5% Tm3+, 10% Yb3+ powder was changed into cubic and monoclinic phase Gd2O3: 0.5% Tm3+, 10% Yb3+ phosphors. Crystalline phases and morphologies of as-prepared powder and phosphors were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM).

Chunyan Cao; Xianmin Zhang; Minglun Chen; Weiping Qin; Jisen Zhang

2010-01-01

28

Nanopatterned PMMA-Yb:Er/Tm:Lu2O3 composites with visible upconversion emissions  

NASA Astrophysics Data System (ADS)

Nanopillars, nanotubes and nanofibers of transparent polymethyl methacrylate (PMMA) polymer with Yb:Ln:Lu2O3 (Ln = Er or Tm) nanoparticles (NPs) (?30–35 nm average size) have been prepared by infiltration of anodized aluminum oxide hexagonally nanopatterned templates. The outer diameter of these nanostructures is in the 330–400 nm range, with lengths up to 50 ?m and a period distance of 430 nm. These nanostructures show visible upconversion (UC) emissions under excitation with 978 nm light. The steady state temperature of the polymer nanostructures is optically evidenced by the Er3+ UC emission and optically controlled around the PMMA glass transition temperature by the excitation light, introducing a new method for NP storage in a solid and potential optically induced particle release. Full color emission is shown in tridoped (Yb:Er:Tm) samples.

Han, X.; Maiz, J.; Mijangos, C.; Zaldo, C.

2014-05-01

29

Nanopatterned PMMA-Yb:Er/Tm:Lu2O3 composites with visible upconversion emissions.  

PubMed

Nanopillars, nanotubes and nanofibers of transparent polymethyl methacrylate (PMMA) polymer with Yb:Ln:Lu2O3 (Ln = Er or Tm) nanoparticles (NPs) (?30-35 nm average size) have been prepared by infiltration of anodized aluminum oxide hexagonally nanopatterned templates. The outer diameter of these nanostructures is in the 330-400 nm range, with lengths up to 50 ?m and a period distance of 430 nm. These nanostructures show visible upconversion (UC) emissions under excitation with 978 nm light. The steady state temperature of the polymer nanostructures is optically evidenced by the Er(3+) UC emission and optically controlled around the PMMA glass transition temperature by the excitation light, introducing a new method for NP storage in a solid and potential optically induced particle release. Full color emission is shown in tridoped (Yb:Er:Tm) samples. PMID:24784527

Han, X; Maiz, J; Mijangos, C; Zaldo, C

2014-05-23

30

An Overview of 166Er, 169Tm and 170Yb Mössbauer Spectroscopy  

NASA Astrophysics Data System (ADS)

The hyperfine splittings of the nuclear energy levels in rare-earth (R) isotopes are sensitive measures of the complex interplay between magnetic exchange and electrostatic crystal-field interactions operating at the atomic level. Mössbauer spectroscopy has been used to great effect in the on-going investigation of these fundamental interactions in R compounds and in this paper we present an overview of 166Er, 169Tm and 170Yb Mössbauer spectroscopy. In particular, we derive expressions for the nuclear energy level splittings incorporating both magnetic and electric quadrupole interactions, using second-order perturbation theory. Such expressions provide a useful means of fitting experimental spectra and also yield criteria for determining whether or not a proposed set of energy level values is physical or not. We also present a number of useful rules of thumb for the analysis of 166Er, 169Tm and 170Yb Mössbauer spectra and, as such, this paper is in effect a Resource Letter.

Cadogan, J. M.; Ryan, D. H.

31

Thermoelectric properties of Yb(x)Eu(1-x)Cd2Sb2.  

PubMed

The thermoelectric performance of EuCd(2)Sb(2) and YbCd(2)Sb(2) was improved by mixed cation occupation. The composition, structure, and thermoelectric properties of Yb(x)Eu(1-x)Cd(2)Sb(2) (x=0, 0.5, 0.75, and 1) have been investigated. Polycrystalline samples are prepared by direct reaction of the elements. Thermoelectric properties were investigated after densification of the materials by spark plasma sintering. Yb(x)Eu(1-x)Cd(2)Sb(2) crystallizes in the P3m1 space group. The lattice parameters increase with the europium content. These materials show low electrical resistivity, high Seebeck coefficient, and low thermal conductivity together with high carrier concentration and high carrier mobility. ZT values of 0.88 and 0.97 are obtained for Yb(0.5)Eu(0.5)Cd(2)Sb(2) and Yb(0.75)Eu(0.25)Cd(2)Sb(2) at 650 K, respectively. PMID:21090867

Zhang, H; Fang, L; Tang, M-B; Man, Z Y; Chen, H H; Yang, X X; Baitinger, M; Grin, Y; Zhao, J-T

2010-11-21

32

Yttrium oxysulfide nanosized spherical particles doped with Yb and Er or Yb and Tm: efficient materials for up-converting phosphor technology field  

Microsoft Academic Search

This work reports on the preparation, structural and luminescent studies of nanosized up-converter phosphors Y2O2S:Yb(4%), Er(0.1%) and Y2O2S:Yb(4%), Tm(0.1%), both from polymeric and basic carbonate precursors. The precursors were submitted to a sulphuration process that was previously developed for oxysulfide preparation from basic carbonate. From XRD data, all phosphors presented the oxysulfide phase and the mean crystallite size estimated from

Ana Maria Pires; Osvaldo Antonio Serra; Marian Rosaly Davolos

2004-01-01

33

Spin-reorientation transitions in Er, Tm and Yb orthoferrites: magnetic and structural properties.  

NASA Astrophysics Data System (ADS)

Magnetic and structural characteristics of ErFeO3, TmFeO3 and YbFeO3 single crystals were studied over a wide temperature range. Magnetic measurements found that the spin-rotation transitions in all crystals are well described by the earlier proposed theory with no fitting parameters. Additionally, they have shown the absence of the magnetic compensation point in TmFeO3, and a noticeable growth of the c-axis magnetization at low temperatures in TmFeO3 and ErFeO3. The X-ray measurements found no symmetry-lowering lattice distortions during the reorientation. Overall, the measurements cover a wide range of material parameters and demonstrate the generality of the modified mean field theory of the ?4->?24->?2 orientation phase transitions in orthoferrites. // L. T. Tsymbal et al., J. Appl. Phys 101, 123919 (2007).

Bazaliy, Ya. B.; Tsymbal, L. T.; Derkachenko, V. N.; Kamenev, V. I.; Kakazei, G. N.; Palomares, F. J.; Wigen, P. E.

2008-03-01

34

Blue, green and 0.8 ?m Tm 3+, Ho 3+ doped upconversion laser glasses, sensitized by Yb 3+  

Microsoft Academic Search

To obtain efficient upconversion laser glass, the optical properties of Tm3+ and Ho3+ were investigated in various glasses. Fluoride glass was selected as base glass for upconversion. The efficient upconversion fluorescences corresponding to the 1G4?3H6 and 3H4?3H6 transitions of Tm3+ and the 5S2?5I8 transition of Ho3+ were observed in Yb3+-Tm3+ and Yb3+-Ho3+ doped aluminozircofluoride glasses excited at 980 nm. The

Bo Peng; Tetsuro Izumitani

1995-01-01

35

Multicolor upconversion emission and energy transfer mechanism in Er3+/Tm3+/Yb3+ codoped tellurite glasses  

NASA Astrophysics Data System (ADS)

A novel Er3+, Tm3+ and Yb3+ codoped tellurite glasses with composition of TeO2-Bi2O3-ZnO-Na2O was prepared by conventional melt-quenching technique to realize the multicolor upconversion (UC) emissions. The absorption spectrum, UC emission spectrum, Raman spectrum, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) curves were measured to characterize the prepared glass samples. Under the excitation of 980 nm laser diode (LD), bright multicolor luminescence composed of red, green and/or blue UC emissions corresponding to the transitions 4F9/2?4I15/2, 2H11/2(4S3/2)?4I15/2 of Er3+ and 1G4?3H6 of Tm3+ were observed in the Er3+/Yb3+, Tm3+/Yb3+ and Er3+/Tm3+/Yb3+ codoped glass samples, which were mainly attributed to the successive energy transfers from Yb3+ to Er3+ and Tm3+, respectively. The energy transfer mechanisms from the Yb3+:2F5/2 level to Er3+:4I11/2 and Tm3+:3H5 levels were further investigated by quantitatively calculating the energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the difference (?T=Tx-Tg) between the glass crystallization onset temperature (Tx) and the transition temperature (Tg) which increase slightly with rare-earth (RE) doped concentration, was larger than 140 °C for all glass samples. Furthermore, the amorphous nature of glass structure was demonstrated by the measured XRD curves. The excellent thermal stability and multicolor luminescent characteristic indicate that the present investigated Er3+/Tm3+/Yb3+ codoped tellurite glasses could be used in the fields of solid state multicolor displays and other luminescent devices.

Peng, Shengxi; Yang, Fengjing; Wu, Libo; Qi, Yawei; Zheng, Shichao; Yin, Dandan; Wang, Xunsi; Zhou, Yaxun

2014-11-01

36

Enhanced near-infrared upconversion luminescence of GdF3:Yb3+, Tm3+ by Li+.  

PubMed

GdF3:0.23Yb3+, 0.005Tm3+, x%Li+ (x = 0-7) NIR to NIR upconversion nanocrystals (UCNPs) were synthesized by a hydrothermal method. Their XRD patterns show that they are all orthorhombic phase despite of different Li+ ion concentrations. The detailed analysis indicates that lithium ions substitute Gd3+ sites at x < 3. As the Li+ content increases, more Li+ ions enter host lattice interstitially. The doped Li+ ions affect the crystal field symmetry around Tm3+ ions, which results in the change of the irradiation transition probabilities between their corresponding transition levels. Compared with GdF3:0.23Yb3+, 0.005Tm3+, the NIR to NIR upconversion emission intensity of GdF3:0.23Yb3+, 0.005Tm3+, 0.03Li+ nanocrystals (excitation at 980 nm, emission at 808 nm) increases 2.2 times. PMID:24734614

Chuai, Xiaohong; Liu, Zhenyu; Liu, Ye; He, Chunfeng; Qin, Weiping

2014-05-01

37

Growth, thermal, and spectroscopic properties of a Cr,Yb,Ho,Eu:YAP laser crystal  

NASA Astrophysics Data System (ADS)

A new Cr,Yb,Ho,Eu:YAlO3(YAP) laser crystal was successfully grown by the Czochralski method. Thermal properties were investigated along the a, b, and c crystalline axes. Results indicate that the Cr,Yb,Ho,Eu:YAP crystal has large anisotropic thermal expansion and that the suitable crystal growth direction is the b axis. The Debye temperatures were fitted, and the lattice vibration frequencies were calculated. Spectroscopic measurements show that Cr3+ and Yb3+ can be used as sensitizers of Ho3+ ions, and Eu3+ ions can play a role of the deactivator in decreasing the lifetime of laser lower level 5I7 from 8.69 ms to 1.89 ms, which is beneficial in decreasing laser threshold and increasing laser conversion efficiency. All these findings suggest that the Cr,Yb,Ho,Eu:YAP crystal is a new potential candidate for realizing 2.8-3 ?m laser output pumped by a 970 nm laser diode or pulsed flash lamp.

Zhang, Huili; Sun, Dunlu; Luo, Jianqiao; Chen, Jiakang; Yang, Huajun; Xiao, Jingzhong; Zhang, Qingli; Yin, Shaotang

2014-06-01

38

Near-infrared photocatalysis of ?-NaYF4:Yb3+,Tm3+@ZnO composites.  

PubMed

A novel near-infrared (NIR)-responsive photocatalyst, ?-NaYF4:Yb(3+),Tm(3+)@ZnO composites, was prepared by a two-step high temperature thermolysis method. In the NIR-responsive photocatalysis, ?-NaYF4:Yb,Tm served as a NIR-to-UV upconverter and provided "UV light" or "necessary energy" to the ZnO catalyst. The energy transfer in the composites and the mixtures of ?-NaYF4:Yb,Tm and ZnO was studied by using steady-state and dynamic fluorescence spectroscopy. The NIR photocatalytic activities were investigated by the decomposition of Rhodamine B. It was found that the energy transfer processes dominated the overall photocatalytic activities, and the generation of hydroxyl radicals was the origin of organic pollutant decomposition under NIR irradiation. PMID:23897044

Guo, Xingyuan; Song, Weiye; Chen, Changfeng; Di, Weihua; Qin, Weiping

2013-09-21

39

Emission properties of hydrothermal Yb3 + , Er3 + and Yb3 + , Tm3 + -codoped Lu2O3 nanorods: upconversion, cathodoluminescence and assessment of waveguide behavior  

NASA Astrophysics Data System (ADS)

Yb3 + and Ln3 + (Ln3 + = Er3 + or Tm3 + ) codoped Lu2O3 nanorods with cubic Ia\\bar 3 symmetry have been prepared by low temperature hydrothermal procedures, and their luminescence properties and waveguide behavior analyzed by means of scanning near-field optical microscopy (SNOM). Room temperature upconversion (UC) under excitation at 980 nm and cathodoluminescence (CL) spectra were studied as a function of the Yb + concentration in the prepared nanorods. UC spectra revealed the strong development of {Er}^{3+}\\,^{4} {F}_{9/2}\\to {}^4 {I}_{15/2} (red) and {Tm}^{3+}\\,{}^{1} {G}_{4} \\to {}^{3} {H}_{6} (blue) bands, which became the pre-eminent and even unique emissions for corresponding nanorods with the higher Yb3 + concentration. Favored by the presence of large phonons in current nanorods, UC mechanisms that privilege the population of 4F9/2 and 1G4 emitting levels through phonon-assisted energy transfer and non-radiative relaxations account for these observed UC luminescence features. CL spectra show much more moderate development of the intensity ratio between the {Er}^{3+}\\, {}^{4} {F}_{9/2} \\to {}^4 {I}_{15/2} (red) and 2H11/2, ^{4} {S}_{3/2}\\to {}^{4} {I}_{15/2} (green) emissions with the increase in the Yb3 + content, while for Yb3 + , Tm3 + -codoped Lu2O3 nanorods the dominant CL emission is {Tm}^{3+}\\,{}^{1} {D}_{2}\\to {}^{3} {F}_{4} (deep-blue). Uniform light emission along Yb3 + , Er3 + -codoped Lu2O3 rods has been observed by using SNOM photoluminescence images; however, the rods seem to be too thin for propagation of light.

Barrera, Elixir William; Cinta Pujol, María; Díaz, Francesc; Choi, Soo Bong; Rotermund, Fabian; Park, Kyung Ho; Jeong, Mun Seok; Cascales, Concepción

2011-02-01

40

Emission properties of hydrothermal Yb(3+), Er(3+) and Yb(3+), Tm(3+)-codoped Lu2O3 nanorods: upconversion, cathodoluminescence and assessment of waveguide behavior.  

PubMed

Yb(3+) and Ln(3+) (Ln(3+) = Er(3+) or Tm(3+)) codoped Lu(2)O(3) nanorods with cubic Ia3 symmetry have been prepared by low temperature hydrothermal procedures, and their luminescence properties and waveguide behavior analyzed by means of scanning near-field optical microscopy (SNOM). Room temperature upconversion (UC) under excitation at 980 nm and cathodoluminescence (CL) spectra were studied as a function of the Yb(+) concentration in the prepared nanorods. UC spectra revealed the strong development of Er(3+) (4)F(9/2) ? (4)I(15/2) (red) and Tm(3+) (1)G(4) ? (3)H(6) (blue) bands, which became the pre-eminent and even unique emissions for corresponding nanorods with the higher Yb(3+) concentration. Favored by the presence of large phonons in current nanorods, UC mechanisms that privilege the population of (4)F(9/2) and (1)G(4) emitting levels through phonon-assisted energy transfer and non-radiative relaxations account for these observed UC luminescence features. CL spectra show much more moderate development of the intensity ratio between the Er(3+) (4)F(9/2) ? (4)I(15/2) (red) and (2)H(11/2), (4)S(3/2) ? (4)I(15/2) (green) emissions with the increase in the Yb(3+) content, while for Yb(3+), Tm(3+)-codoped Lu(2)O(3) nanorods the dominant CL emission is Tm(3+) (1)D(2) ? (3)F(4) (deep-blue). Uniform light emission along Yb(3+), Er(3+)-codoped Lu(2)O(3) rods has been observed by using SNOM photoluminescence images; however, the rods seem to be too thin for propagation of light. PMID:21233550

Barrera, Elixir William; Pujol, María Cinta; Díaz, Francesc; Choi, Soo Bong; Rotermund, Fabian; Park, Kyung Ho; Jeong, Mun Seok; Cascales, Concepción

2011-02-18

41

Broadband downconversion based infrared quantum cutting by cooperative energy transfer from Eu2+ to Yb3+ in glasses  

NASA Astrophysics Data System (ADS)

Near-infrared quantum cutting involving the emission of near-infrared photons by downconversion cooperative energy transfer from Eu2+ to Yb3+ in borate glasses was reported. Electron spin resonance spectra and absorption spectra were measured to prove the existence of Eu2+ in borate glasses. Excitation, emission, and fluorescence decay measurements were performed to examine the occurrence of cooperative energy transfer from Eu2+ to Yb3+ ions. Yb3+ concentration dependent quantum efficiency was calculated and the maximum efficiency approaches 164.19%.

Zhou, Jiajia; Zhuang, Yixi; Ye, Song; Teng, Yu; Lin, Geng; Zhu, Bin; Xie, Junhua; Qiu, Jianrong

2009-10-01

42

Intrinsic single-band upconversion emission in colloidal Yb/Er(Tm):Na3Zr(Hf)F7 nanocrystals.  

PubMed

Novel Yb/Er(Tm):Na(3)MF(7) (M = Zr, Hf) nanocrystals with intrinsic single-band upconversion emission, in contrast to the routine lanthanide-doped fluoride nanocrystals which show typical multi-band upconversion emissions, are reported for the first time. Specifically, the red upconversion intensity of the Yb/Er:Na(3)ZrF(7) nanocrystals is about 5 times as high as that of the hexagonal Yb/Er:NaYF(4) ones with a similar crystal size. PMID:23010848

Chen, Daqin; Lei, Lei; Zhang, Rui; Yang, Anping; Xu, Ju; Wang, Yuansheng

2012-11-01

43

Red, green, blue and white light upconversion emission in Yb3+\\/Tm3+\\/Ho3+ co-doped tellurite glasses  

Microsoft Academic Search

Several Yb3+\\/Tm3+\\/Ho3+ co-doped transparent TeO2-ZnO-Na2O-Yb2O3-Ho2O3-Tm2O3 glasses were prepared and luminescence properties were characterized. Simultaneous red, green and blue (RGB) emission were obtained after excitation at 970 nm. Colour emission was tuned from multicolour to white light with colour coordinate (0.32, 0.33) matching very well with the white reference (0.33, 0.33). Changes in colour emission were obtained by varying the intensity

H. Desirena; E. De la Rosa; P. Salas; O. Meza

2011-01-01

44

Mechanisms and concentrations dependence of up-conversion luminescence in Tm 3+\\/Yb 3+ codoped oxyfluoride glass-ceramics  

Microsoft Academic Search

The up-conversion properties of Tm3+\\/Yb3+ codoped oxyfluoride glass-ceramics under 980 nm excitation were investigated. Intense blue up-conversion luminescence due to the Tm3+: 1G4?3H6 transition was observed in the glass-ceramics. The intensity of the blue up-conversion luminescence in a 1 mol% YbF3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The up-conversion mechanism

Junjie Zhang; Dongbing He; Zhongchao Duan; Liyan Zhang; Shixun Dai; Lili Hu

2005-01-01

45

White upconversion emission in Li+/Yb3+/Tm3+/Er3+-doped Gd6MoO12 phosphors  

NASA Astrophysics Data System (ADS)

The Yb3+/Er3+/Tm3+-doped Gd6MoO12 phosphors and Li+/Yb3+/Er3+/Tm3+-doped Gd6MoO12 phosphors were synthesized by the high-temperature solid-state method. Under 980 nm laser diode excitation, the Gd6MoO12:Li+/Yb3+/Er3+/Tm3+ phosphors show the white upconversion (UC) emission at the pump power of 200 mW/cm2, which is composed of the blue (1G4?3H6 of Tm3+), green (2H11/2, 4S3/2?4I15/2 of Er3+), and red (4F9/2?4I15/2 of Er3+) UC emissions. The calculated CIE color coordinates of Gd6MoO12:Tm3+/Er3+/Yb3+ phosphors changed from blue area to white area after the Li+ ion doping. Then, the effect of Li+ ions mixing on the emission was analysed. The relative UC mechanisms and properties were also investigated and proposed based on their spectral. The additional mixed Li+ ions enhanced the red and green upconversion emission largely in this phosphor and then formed the white UC emission, which indicated that the Li+ is a promising dopant for tuning white light luminescence in some case.

Sun, Jiayue; Xue, Bing; Du, Haiyan

2013-07-01

46

Upconversion color tunability and white light generation in Tm 3+\\/Ho 3+\\/Yb 3+ doped aluminum germanate glasses  

Microsoft Academic Search

Tm3+\\/Ho3+\\/Yb3+ triply doped aluminum germanate glasses exhibiting multicolor upconversion fluorescences have been fabricated and characterized. Efficient three-photon blue upconversion emission of Tm3+ and two-photon green and red upconversion fluorescences of Ho3+ have been observed. The strong red emission of Ho3+, which is more than eight times higher than that of the green emission, is desirable in achieving high color rendering

Hua Gong; Dianlai Yang; Xin Zhao; Edwin Yun Bun Pun; Hai Lin

2010-01-01

47

Infrared spectra of dinitrogen adsorbed on bimetallic lanthanide (Eu or Yb)–Ni\\/SiO 2 catalysts  

Microsoft Academic Search

Bimetallic lanthanide (Ln: Eu or Yb)–Ni\\/SiO2 catalysts prepared by the use of dissolution of lanthanide metals in liquid ammonia have been studied by infrared spectroscopy\\u000a for dinitrogen adsorption. The infrared spectra were measured at 133–300 K using Ln–Ni\\/SiO2 obtained when the Eu or Yb metal dissolved in liquid ammonia reacted with 20 mass% Ni\\/SiO2 in different ratios. Infrared spectra for

Hayao Imamura; Yoshihisa Sakata; Yoshie Kasuga; Susumu Tsuchiya

1999-01-01

48

Intrinsic bistability effect of Yb-sensitized Tm upconversion emission in zirconium dioxide nanocrystal  

NASA Astrophysics Data System (ADS)

Intrinsic bistability in active optical compounds doped with rare-earth ions has attracted widespread interest because of its relevance for optical signal switching and routing. In this paper, room temperature strong bistability effect of Ybsensitized Tm upconversion emission is reported in zirconium dioxide nanocrystal host matrix under infrared diode laser irradiation. The distinct optical bistability behavior is simultaneously observed in three emission bands of Tm ion around 480, 650/680 and 800 nm which are assigned to the radiative transitions of 1G4-->3H6, 1G4-->3F4/3F2,3-->3H6, and 3H4-->3H6, respectively. The bistability loops exhibit uniformly clockwise cycle characterized by a relatively lower trace of emission intensity at decreasing pump power than the trace at increasing pump power. Multiphoton upconversion processes are analyzed to determine the Yb-->Tm energy transfer mechanism. Such strong bistability effect is associated with thermally enhanced nonradiative decay and reduced luminescence quantum yield due to the strong pump-induced local thermal loading.

Wang, D. X.; Nie, M.; Zhang, Z. G.; Li, H.; Li, L.; Zhang, X. L.; Zhang, X. W.; Li, R. M.

2012-01-01

49

Electronic structure of RAuMg and RAgMg (R=Eu,Gd,Yb)  

NASA Astrophysics Data System (ADS)

We have investigated the electronic structure of the equiatomic EuAuMg , GdAuMg , YbAuMg , and GdAgMg intermetallics using x-ray photoelectron spectroscopy. The spectra revealed that the Yb and Eu are divalent while the Gd is trivalent. The spectral weight in the vicinity of the Fermi level is dominated by the mix of Mgs , Au/Agsp , and Rspd bands. We also found that the Au and Agd bands are extraordinarily narrow, as if the noble metal atoms were impurities submerged in a low density sp metal host. The experimental results were compared with band structure calculations, and we found good agreement provided that the spin-orbit interaction in the Au an Agd bands is included and correlation effects in an open 4f shell are accounted for.

Gegner, Jan; Koethe, T. C.; Wu, Hua; Hu, Z.; Hartmann, H.; Lorenz, T.; Fickenscher, T.; Pöttgen, R.; Tjeng, L. H.

2006-08-01

50

Enhanced near-infrared photocatalysis of NaYF4:Yb, Tm/CdS/TiO2 composites.  

PubMed

The previous works by our group (Chem. Commun., 2010, 46, 2304-2306; ACS Catal., 2013, 3, 405-412; Phys. Chem. Chem. Phys., 2013, 15, 14681-14688) have reported the near-infrared-driven photocatalysis of broadband semiconductor TiO2 or ZnO that was combined with upconverting luminescence particles to form a core-shell structure. However, the photocatalytic efficiency is low for this new type of photocatalysts. In this work, NaYF4:Yb,Tm/CdS/TiO2 composites for NIR photocatalysis were prepared by linking CdS and TiO2 nanocrystals on the NaYF4:Yb,Tm microcrystal surfaces. CdS and TiO2 were well interacted to form a heterojunction structure. The energy transfer between NaYF4:Yb,Tm and the semiconductors CdS and TiO2 was investigated by steady-state and dynamic fluorescence spectroscopy. The photocatalytic activities of the as-prepared composites were evaluated by the degradation of methylene blue in aqueous solution upon NIR irradiation. Significantly, it was found that the united adhesions of CdS and TiO2 on the NaYF4:Yb,Tm particle surfaces showed much higher catalytic activities than the individual adhesion of CdS or TiO2 on the NaYF4:Yb,Tm surfaces. This was attributed mainly to the effective separation of the photogenerated electron-hole pairs due to the charge transfer across the CdS-TiO2 interface driven by the band potential difference between them. The presented composite structure of upconverting luminescence materials coupled with narrow/wide semiconductor heterojunctions provides a new model for improved NIR photocatalysis. PMID:24162269

Guo, Xingyuan; Di, Weihua; Chen, Changfeng; Liu, Chunxu; Wang, Xue; Qin, Weiping

2014-01-21

51

White light upconversion emission in Yb3+/ Er3+/ Tm3+ codoped oxy-fluoride lithium tungsten tellurite glass ceramics  

NASA Astrophysics Data System (ADS)

The bright white upconversion emission ( tri-colour UC) is generated in Er/Tm/Yb tri -doped oxy-fluoride lithium tungsten tellurite (TWLOF)glass ceramics containing crystalline phase LiYbF4 under the excitation of 980nm laser diode. The most appropriate combination of rare-earth ions (2mol% YbF3 1mol% ErF3 and 1mol%TmF3 )of glass ceramic sample has been determined to tune the primary colour (RGB and generate white light emission. By varying the pump power, intense and weak blue (487nm, 437nm), green (525nm and 545nm) and red (662nm) emission are simultaneously observed at room temperature. The dependence of upconversion emission intensity suggest that a theephoton process is responsible for the blue emission of Tm3+ ions and red emission due to both Tm3+ and Er3+ ions , while green emission originated from two photon processes in Er3+ ions. Also tri colour upconvesion and energy transfer in this glass ceramics sample were studied under 808nm laser diode excitation. The Upconversion mechanisms and Tm3+ ions plays role of both emitter and activator (transfer energy to Er) were discussed.

Ansari, Ghizal F.; Mahajan, S. K.

2012-02-01

52

Broadband near-infrared downconversion luminescence in Eu2+-Yb3+ codoped Ca9Y(PO4)7  

NASA Astrophysics Data System (ADS)

An efficient broadband near-infrared (NIR) quantum cutting was demonstrated in Eu2+-Yb3+ codoped Ca9Y(PO4)7 phosphor. Upon excitation of Eu2+ ions to the 4f65d1 level with an ultraviolet photon at 322 nm, emissions of two NIR photons at 983 nm of Yb3+were achieved. The dependences of the visible and NIR emissions, the decay lifetime, the energy transfer efficiency (ETE), and the quantum efficiency (QE) on the Yb3+ doping content were investigated in detail. The results indicated that the maximum ETE and the corresponding downconversion QE can reach between 80% and 179%, respectively.

Sun, Jiayue; Zhou, Wei; Sun, Yining; Zeng, Junhui

2013-06-01

53

Two-color optically synchronized ultrashort pulses from a Tm/Yb-co-doped fiber amplifier.  

PubMed

A method of producing high quality, optically synchronized two-color ultrashort pulses in an active thulium-doped fiber is proposed. We show that sech-shaped femtosecond pulses with essentially different wavelengths can be generated directly from a Tm/Yb-co-doped amplifier: one pulse at about 2 ?m and the second pulse with a tunable wavelength up to 2.3 ?m, which covers the pump and gain regions of Cr:ZnSe and Cr:ZnS amplifiers. The shortest pulses with durations of 145 fs at 2.25 ?m and 125 fs at 2 ?m were measured by the FROG (frequency-resolved optical gating) technique. PMID:24686661

Koptev, M Yu; Anashkina, E A; Andrianov, A V; Muravyev, S V; Kim, A V

2014-04-01

54

[Direct upconversion sensitization luminescence of Tm(0.1)Yb(10.9): oxyfluoride glass].  

PubMed

This paper studied the direct upconversion sensitization luminescence of Tm(0.1)Yb(10.9): oxyfluoride glass pumped by 966 nm diode laser. We found that there are strong 474 nm three-photon upconversion fluorescence of 1G4-->3H6 transition. As well as there are weak 362, 452 and 650 nm three-photon upconversion fluorescence of 1D2-->3H6, 1D2-->3F4, 1G4-->3F4 and 681 nm two-photon upconversion fluorescence of 3F3-->3H6 transitions respectively. Their upconversion mechanism has been analyzed and discussed simply. PMID:12958885

Chen, X B; Sawanobori, N; Song, Z F

2001-12-01

55

[The upconversion luminescence of Tm(0.35)Yb(5):FOV nanophase oxyfluoride vitroceramics].  

PubMed

The upconversion luminescence of nanophase oxyfluoride vitroceramics Tm(0.35)Yb(5) : FOV when excited by a 975 nm diode laser was studied in the present paper. Several ultraviolet upconversion luminescence lines positioned at 363.6 nm, (462.6 nm, 477.0 nm), 648.7 nm, (699.7 nm, 680.7 nm) and (777.6 nm, 800.7 nm) were found. They can be attributed to the fluorescence transitions of 1 D2-->3 H6, 1 G4-->3 H6, 1 G4-->3 F4, 3 F3-->3 H6 and 3 H4-->3 H6 of Tm3+ ion. The careful measurement and analysis of the variation of upconversion luminescence intensity F as a function of the 975 nm pumping laser power P has proven that the upconversion luminescence of 1 D2 state is partly a five-photon upconversion luminescence, while the upconversion luminescence of 1 G4 and 3 H4 state is the three-photon and two-photon upconversion luminescence respectively. PMID:18975790

Chen, Xiao-bo; Wang, Ya-fei; Sawanobori, Naruhito; Yang, Guo-jian; Cui, Jian-sheng; He, Chen-juan; Chen, Zhi-jian; Liu, Da-he; Peng, Fang-lin; Song, Zeng-fu

2008-08-01

56

Diode-pumped 2 ?m vibronic (Tm3+, Yb3+):KLu(WO4)2 laser.  

PubMed

We report on laser operation in a (6 at. % Tm, 5 at. % Yb):KLu(WO4)2 codoped crystal. The vibrational frequencies of KLu(WO4)2 are coupled to the electronic transitions of Tm3+ at 1946 nm, creating virtual final laser levels at higher energy than the ground level 3H6 of Tm3+. The longest recorded laser wavelength was 2039 nm, which is longer than permitted by a pure electronic transition in Tm3+ ions in KLu(WO4)2. We show that every laser wavelength can be explained with the electron-phonon coupling effect, where the vibration frequencies were determined through Raman spectroscopy. PMID:22614492

Segura, Martha; Mateos, Xavier; Pujol, Maria Cinta; Carvajal, Joan Josep; Aguiló, Magdalena; Díaz, Francesc; Griebner, Uwe; Petrov, Valentin

2012-05-10

57

Thermoelectric properties of Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2}  

SciTech Connect

The thermoelectric performance of EuCd{sub 2}Sb{sub 2} and YbCd{sub 2}Sb{sub 2} was improved by mixed cation occupation. The composition, structure, and thermoelectric properties of Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2} (x=0, 0.5, 0.75, and 1) have been investigated. Polycrystalline samples are prepared by direct reaction of the elements. Thermoelectric properties were investigated after densification of the materials by spark plasma sintering. Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2} crystallizes in the P3m1 space group. The lattice parameters increase with the europium content. These materials show low electrical resistivity, high Seebeck coefficient, and low thermal conductivity together with high carrier concentration and high carrier mobility. ZT values of 0.88 and 0.97 are obtained for Yb{sub 0.5}Eu{sub 0.5}Cd{sub 2}Sb{sub 2} and Yb{sub 0.75}Eu{sub 0.25}Cd{sub 2}Sb{sub 2} at 650 K, respectively.

Zhang, H. [Key Laboratory of Transparent Opto-Functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 200050 Shanghai (China); Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Str. 40, 01187 Dresden (Germany); Fang, L. [State Key Laboratory Breeding Base of Nonferrous Metals and Specific Materials Processing, Guilin University of Technology, Guilin 541004 (China); Tang, M.-B.; Man, Z. Y.; Chen, H. H.; Yang, X. X.; Zhao, J.-T. [Key Laboratory of Transparent Opto-Functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 200050 Shanghai (China); Baitinger, M.; Grin, Y. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Str. 40, 01187 Dresden (Germany)

2010-11-21

58

Tm3+/Er3+/Yb3+ tri-doped TeO2-PbF2-AlF3 glass for white-light-emitting diode  

NASA Astrophysics Data System (ADS)

By the high temperature melting method, Er3+/Yb3+, Tm3+/Yb3+, and Tm3+/Er3+/Yb3+ co-doped oxyfluoride telluride glasses with the compositions of (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.2Er2O3), (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.5Tm2O3), and (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.2Er2O3-0.5Tm2O3) (mol%) were prepared. The emission spectra of the samples were measured under 975 nm excitation. The emission color of Tm3+/Er3+/Yb3+ tri-doped glass is white to the naked eye. The International Commission on Illumination (CIE) coordinates (0.353,0.308) of the sample are close to the equal energy white-light illumination standard (x=0.333,y=0.333) and the color temperature is 4381 K. Our research will be helpful in developing luminescent materials for white light-emitting-diodes (LEDs).

Ming, Chengguo; Song, Feng; Ren, Xiaobin; An, Liqun; Qin, Yueting

2013-09-01

59

Thulium concentration quenching in the up-converting ?-Tm3+/Yb3+ NaYF4 colloidal nanocrystals  

NASA Astrophysics Data System (ADS)

Luminescence spectra, power dependence and luminescence lifetimes were measured and studied in pure cubic phase NaYF4:20%Yb3+, x%Tm3+ (where x = 0.1%, 0.2%, 0.5%, 1% and 2%) nanocolloidal phosphors synthesized by thermal decomposition. Increasing concentration of Tm3+ ions led to decrease of luminescence intensity, increase in the slopes of power dependence as well as to the decrease in the luminescence decay- and rise-times, helping to resolve the mechanisms of up-conversion and concentration quenching.

Misiak, Ma?gorzata; Prorok, Katarzyna; Cichy, Bart?omiej; Bednarkiewicz, Artur; Str?k, Wies?aw

2013-03-01

60

Red, green, blue and white light upconversion emission in Yb3+/Tm3+/Ho3+ co-doped tellurite glasses  

NASA Astrophysics Data System (ADS)

Several Yb3+/Tm3+/Ho3+ co-doped transparent TeO2-ZnO-Na2O-Yb2O3-Ho2O3-Tm2O3 glasses were prepared and luminescence properties were characterized. Simultaneous red, green and blue (RGB) emission were obtained after excitation at 970 nm. Colour emission was tuned from multicolour to white light with colour coordinate (0.32, 0.33) matching very well with the white reference (0.33, 0.33). Changes in colour emission were obtained by varying the intensity ratios between RGB bands that are strongly concentration dependent because of the interaction of co-dopants. The colour tunability, high quality of white light and high intensity of the emitted signal make these transparent glasses excellent candidates for applications in solid-state lighting.

Desirena, H.; De la Rosa, E.; Salas, P.; Meza, O.

2011-11-01

61

Magnons and crystal-field transitions in hexagonal RMnO3 (R = Er, Tm, Yb, Lu) single crystals  

NASA Astrophysics Data System (ADS)

Far-infrared optical transmission spectra of the antiferromagnetic resonances, or magnons, and crystal-field (CF) transitions have been studied in hexagonal RMnO3 (R = Er, Tm, Yb, Lu) single crystals. The magnon and CF frequencies, their oscillator strengths, and effective g factors have been measured using external magnetic fields up to 9 T in the temperature range between 1.5 and 100 K. The magnon frequency increases systematically with a decrease of the R ion radius. The magnetic ordering of R ions (R = Er, Tm, Yb) was observed at low temperatures T<3.5 K and in strong external magnetic fields. The observed effects are analyzed taking into account the main magnetic interactions in the system including exchange of the Mn3+ spins with R3+ paramagnetic moments.

Standard, E. C.; Stanislavchuk, T.; Sirenko, A. A.; Lee, N.; Cheong, S.-W.

2012-04-01

62

Oxide phosphors for light upconversion; Yb3+ and Tm3+ co-doped Y2BaZnO5  

NASA Astrophysics Data System (ADS)

The optical properties of Yb3+ and Tm3+ co-doped Y2BaZnO5, synthesized by solid-state reaction, are investigated in detail. Three main emission bands centered around 479 nm (blue), 654 nm (red), and 796 nm (near-infrared) are observed under near-infrared laser excitation via an upconversion process. Detailed studies of the upconversion properties as a function of dopant concentrations are described and upconversion efficiencies quantified precisely. Maximum efficiencies of ~ 1.53% in the 730-870 nm near-infrared emission range and of ~ 0.09% in the 420-530 nm blue range are obtained. The results of power dependence studies and concentration dependent lifetime measurements are presented. This in-depth spectroscopic study allows us, for the first time, to identify the dominant processes involved in the upconversion mechanism of Yb3+, Tm3+ co-doped Y2BaZnO5 oxides.

Etchart, Isabelle; Hernández, Ignacio; Huignard, Arnaud; Bérard, Mathieu; Laroche, Marine; Gillin, William P.; Curry, Richard J.; Cheetham, Anthony K.

2011-03-01

63

Luminescence of YAG doped with Eu, Yb, and Mn ions under VUV excitation  

NASA Astrophysics Data System (ADS)

Hydrothermal synthesis has been successfully used to obtain fine-crystalline powders of yttrium aluminum garnet (YAG) doped with manganese ions and codoped with cerium and manganese ions. Using the method of high-temperature solid-state synthesis, ceramic specimens of YAG that contain europium and ytterbium ions have been obtained. In synthesized YAG:Eu and YAG:Yb ceramics, no luminescence that can be attributed to 5 d-4 f transitions in Eu2+ or Yb2+ ions has been detected, even though the scheme of energy levels of these ions constructed with respect to YAG energy bands indicates that there is a potential possibility of the occurrence of 5 d-4 f luminescence for Eu2+ ions in YAG. At room temperature, the luminescence spectrum of hydrothermally synthesized YAG doped with manganese ions consists of two broad bands with maxima at ˜600 and ˜750 nm and does not contain any narrow bands in the red or IR range. Therefore, the spectrum contradicts to the properties of the luminescence of Mn2+, Mn3+, or Mn4+ ions in YAG described in the literature, even though the obtained hydrothermal specimens can contain noticeable concentrations only of Mn3+ ions.

Makhov, V. N.; Khaidukov, N. M.

2014-05-01

64

Upconversion white light of Tm 3+\\/Er 3+\\/Yb 3+ tri-doped CaF 2 phosphors  

Microsoft Academic Search

Tm3+\\/Er3+\\/Yb3+ tri-doped CaF2 phosphors were synthesized using a hydrothermal method. The phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and up-conversion (UC) emission spectra. After annealing, the phosphors emitted white light under a 980nm continuous wave diode laser (CW LD 2 W) excitation. As the excitation power density changed in the range of 20–260W\\/cm2, the

Chunyan Cao; Weiping Qin; Jisen Zhang; Yan Wang; Guofeng Wang; Guodong Wei; Peifen Zhu; Lili Wang; Longzhen Jin

2008-01-01

65

Color tunability with temperature and pump intensity in Yb3+/Tm3+ codoped aluminosilicate glass under anti-Stokes excitation.  

PubMed

Pump and thermally induced color tunabilities were demonstrated in Yb(3+)/Tm(3+) codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 microm. The effects of pump intensity and sample's temperature on the upconversion emissions and mainly on the color tunabilities (from 800 to 480 nm) were investigated. The results revealed a 20- and a threefold reductions at 800/480 nm ratio as, respectively, the pump intensity and sample's temperature were increased from 27 to 700 kW/cm(2) and from 296 to 577 K. These behaviors with pump intensity and temperature (a strong increase of the 480 nm emission in comparison with the 800 nm one) were attributed to the several efficient processes occurring in the LSCAS system (Yb(3+)-->Tm(3+) energy-transfer processes, easy saturations of the Yb(3+) and Tm(3+) excited states, and radiative emissions). Besides these assigns, the temperature dependence is mainly assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process. Theoretical analyses and fits of the experimental data provided quantitative information. PMID:20649337

Silva, W F; Eliel, G S N; dos Santos, P V; de Araujo, M T; Vermelho, M V D; Udo, P T; Astrath, N G C; Baesso, M L; Jacinto, C

2010-07-21

66

Up-conversion luminescence of Tm3+ sensitized by Yb3+ ions in GdVO4  

NASA Astrophysics Data System (ADS)

The aim of this work is to study up-conversion (UPC) luminescence in a series of Tm3+/Yb3+-co-doped GdVO4 samples synthesized by the solid-state method. The concentrations of Yb3+ ions were 3, 6 and 9 mol.%, while the concentration of Tm3+ ions was fixed (3 mol.%). X-ray diffraction patterns for all the synthesized samples confirmed successful formation of a pure GdVO4 phase. Quantitative energy-dispersion x-ray analysis confirmed successful doping of Tm3+ and Yb3+ ions into the GdVO4 matrix. Scanning electron microscope images show that the samples are composed of deformed (irregular) spherical particles with an average diameter size in the range of 1.4 - 8.4 ?m. Up-converted emission spectra were recorded at room temperature under 980 nm excitation. It was found that all our samples exhibit UPC emission in three different spectral regions: strong emissions are observed at 475 and 800 nm corresponding to the 1G4 ? 3H6 and 3H4 ? 3H6 transitions, respectively, while emission in the red region at about 650 nm is very weak and is due to the 1G4 ? 3F4 transition. It was concluded that conversion of near-infrared radiation into blue emission proved to be very effective in all the synthesized systems. It was found that emission decay curves for all samples exhibit single exponential behavior.

Gavrilovi?, T. V.; Nikoli?, M. G.; Jovanovi?, D. J.; Drami?anin, M. D.

2013-11-01

67

Blue up-conversion luminescence and energy transfer process in Nd3+-Yb3+-Tm3+ co-doped ZrF4-based glasses  

NASA Astrophysics Data System (ADS)

Up-conversion luminescence properties and energy transfer processes in Nd3+, Yb3+, and Tm3+ co-doped ZrF4-based fluoride glasses have been studied under 800 nm light excitation. Blue up-converted emission around 478 nm which can be assigned to the Tm3+: 1G4-->3H6 transition, was strongly observed. Up-conversion luminescence intensity exhibited an YbF3-concentration dependence. Among Nd3+, Yb3+, and Tm3+, both Nd3+ and Tm3+ have ground state absorption bands due to the (2H9/2, 4F5/2) <--4I9/2 and 3F4<--3H6 transitions, respectively, which can be directly pumped by 800 nm light. However, no emissions were observed in Tm3+ singly doped and Tm3+-Yb3+ doubly doped glasses under 800 nm excitation. Therefore, a possible up-conversion mechanism may be proposed as follows: Energy transfer firstly occurs from Nd3+ to Yb3+ when Nd3+ is excited by 800 nm light, then the energy is transferred from Yb3+ to Tm3+ which is on the excited state and, finally, blue up-conversion emission of Tm3+ is observed through the Tm3+: 1G4-->3H6 transition. It was also demonstrated that the energy on the Tm3+: 1G4 level was back-transferred to Nd3+ in the Nd3+ high-concentration region, quenching the up-conversion luminescence.

Qiu, Jianbei; Kawamoto, Yoji

2002-02-01

68

Anisotropy of optical properties of hexagonal RMnO3 Manganites ( R = Ho, Er, Tm, Yb)  

NASA Astrophysics Data System (ADS)

The evolution of real and imaginary parts of the complex permittivity of hexagonal single crystals of RMnO3 manganites ( R = Ho, Er, Tm, Yb) differing in the radius of rare-earth ion r R has been studied using spectroscopic ellipsometry in the range of 0.5-5.0 eV at room temperature. Spectra of dielectric functions show a strong polarization dependence. The optical-absorption edge for polarization E ? c is determined by the intense narrow peak at 1.6 eV, whereas for polarization E ? c, the peak is shifted toward high energies by 0.15-0.20 eV and its intensity is suppressed greatly. It has been shown that, when r R decreases, the energy position of the intense peak at 1.6 eV in the spectrum of the imaginary part of the dielectric function for polarization E ? c shifts toward low energies by no more than 0.1 eV, which reflects changes in the local surroundings of the Mn3+ ion. For the both polarizations, a broad absorption band with the center at 2.4 eV has been revealed; the band was detected earlier in the antiferromagnetic phase in nonlinear spectra upon the optical generation of the second harmonic. Spectra of permittivity have been analyzed within available concepts on the electronic structure of hexagonal RMnO3 compounds and have been compared with corresponding spectra of previously studied orthorhombic RMnO3 compounds.

Makhnev, A. A.; Nomerovannaya, L. V.

2013-11-01

69

Multicolor up conversion emission and color tunability in Yb 3+/Tm 3+/Ho 3+ triply doped heavy metal oxide glasses  

NASA Astrophysics Data System (ADS)

Multicolor and white light emissions have been achieved in Yb 3+, Tm 3+ and Ho 3+ triply doped heavy metal oxide glasses upon laser excitation at 980 nm. The red (660 nm), green (547 nm) and blue (478 nm) up conversion emissions of the rare earth (RE) ions triply doped TeO 2-GeO 2-Bi 2O 3-K 2O glass (TGBK) have been investigated as a function of the RE concentration and excitation power of the 980 nm laser diode. The most appropriate combination of RE in the TGBK glass host (1.6 wt% Yb 2O 3, 0.6 wt% Tm 2O 3 and 0.1 wt% Ho 2O 3) has been determined with the purpose to tune the primary colors (RGB) respective emissions and generate white light emission by varying the pump power. The involved infrared to visible up conversion mechanisms mainly consist in a three-photon blue up conversion of Tm 3+ ions and a two-photon green and red up conversions of Ho 3+ ions. The resulting multicolor emissions have been described according to the CIE-1931 standards.

Ledemi, Yannick; Manzani, Danilo; Ribeiro, Sidney J. L.; Messaddeq, Younes

2011-10-01

70

Sensitive detection of NaYF4: Yb/Tm nanoparticles using suspended core microstructured optical fibers  

NASA Astrophysics Data System (ADS)

Rare-earth doped upconversion nanocrystals are emerging as the next-generation luminescent biomaterials. Here we load NaYF4: Yb/Er and NaYF4: Yb/Tm upconversion nanocrystals into a soft-glass suspended-core optical fiber dip sensor, allowing sensitive measurements and power-dependent characterizations to be performed. This, in combination with negligible background autofluorescence from the glass fiber when using infrared excitation has provided a significant improvement in terms of sensitivity over what has previously been demonstrated using an optical fiber dip sensor. For detection we employ suspended-core optical fibers, which have found extensive use in sensing applications. These combine the high evanescent overlap comparable to that of a nanowire, with the robust handling characteristics and long interaction length of a conventional fiber. The fiber sensor platform allows measurements to be performed using minimal sample volumes (<20 nL) while still maintaining the sensitivity of the platform.

Schartner, Erik P.; Jin, Dayong; Zhao, Jiangbo; Monro, Tanya M.

2013-02-01

71

Monodisperse NaYbF4 : Tm3+/NaGdF4 core/shell nanocrystals with near-infrared to near-infrared upconversion photoluminescence and magnetic resonance properties  

NASA Astrophysics Data System (ADS)

We report core/shell NaYbF4 : Tm3+/NaGdF4 nanocrystals to be used as probes for bimodal near infrared to near infrared (NIR-to-NIR) upconversion photoluminescence (UCPL) and magnetic resonance (MR) imaging. The NaYbF4 : Tm3+ nanocrystals were previously reported to produce the intense NIR-to-NIR UCPL peaked at ~800 nm under excitation at ~975 nm. We have found that the growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals results in the increase in the intensity of UCPL of Tm3+ ions by about 3 times. Unlike biexponential PL decay of NaYbF4 : Tm3+ nanocrystals, the PL decay of NaYbF4 : Tm3+/NaGdF4 core/shell nanocrystals is single exponential and of longer lifetime due to the suppression of surface quenching effects for Tm3+ PL. The growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals also provides high MR relaxivity from paramagnetic Gd3+ ions contained in the shell. The T1-weighted MR signal of the (NaYbF4:2% Tm3+)/NaGdF4 nanoparticles was measured to be about 2.6 mM-1s-1. Due to the combined presence of efficient optical and MR imaging capabilities, nanoprobes based on NaYbF4 : Tm3+/NaGdF4 fluoride nanophosphors can be considered as a promising platform for simultaneous bimodal PL and MR bioimaging.We report core/shell NaYbF4 : Tm3+/NaGdF4 nanocrystals to be used as probes for bimodal near infrared to near infrared (NIR-to-NIR) upconversion photoluminescence (UCPL) and magnetic resonance (MR) imaging. The NaYbF4 : Tm3+ nanocrystals were previously reported to produce the intense NIR-to-NIR UCPL peaked at ~800 nm under excitation at ~975 nm. We have found that the growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals results in the increase in the intensity of UCPL of Tm3+ ions by about 3 times. Unlike biexponential PL decay of NaYbF4 : Tm3+ nanocrystals, the PL decay of NaYbF4 : Tm3+/NaGdF4 core/shell nanocrystals is single exponential and of longer lifetime due to the suppression of surface quenching effects for Tm3+ PL. The growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals also provides high MR relaxivity from paramagnetic Gd3+ ions contained in the shell. The T1-weighted MR signal of the (NaYbF4:2% Tm3+)/NaGdF4 nanoparticles was measured to be about 2.6 mM-1s-1. Due to the combined presence of efficient optical and MR imaging capabilities, nanoprobes based on NaYbF4 : Tm3+/NaGdF4 fluoride nanophosphors can be considered as a promising platform for simultaneous bimodal PL and MR bioimaging. Electronic supplementary information (ESI) available: transmission electron images with higher magnification times; histograms of the size distribution of NaYbF4:2% Tm3+ and NaYbF4 : Tm3+/NaGdF4 nanocrystals; d-spacing values of NaYbF4:2% Tm3+ and NaYbF4 : Tm3+/NaGdF4 nanocrystals; mechanisms for upconversion photoluminescence generation. See DOI: 10.1039/c0nr01018a

Chen, Guanying; Ohulchanskyy, Tymish Y.; Law, Wing Cheung; Ågren, Hans; Prasad, Paras N.

2011-05-01

72

Upconversion emissions from high-energy states of Eu3+ sensitized by Yb3+ and Ho3+ in ?-NaYF4 microcrystals under 980 nm excitation.  

PubMed

Under 980 nm excitation, multiple ultraviolet and visible upconversion luminescence from Ho3+ and Eu3+ ions were observed in Yb3+/Ho3+/Eu3+ tri-doped NaYF4 microcrystals (MCs). The high-energy states (5H3-7, 5L6, 5D3 and 5D2) of Eu3+ ions could be efficiently populated by two-step energy transfer (ET) processes of Yb ? Ho ? Eu. Four-, three-, two-photon UC processes of Eu3+ ions were confirmed by the dependence of 5H3-7, 5L6 and 5D0 levels emission intensities on the pumping power. PMID:22273940

Wang, Lili; Liu, Zhenyu; Chen, Zhe; Zhao, Dan; Qin, Guanshi; Qin, Weiping

2011-12-01

73

Enhanced NIR downconversion luminescence by precipitating nano Ca5(PO4)3F crystals in Eu2+-Yb3+ co-doped glass.  

PubMed

Eu(2+)-Yb(3+) co-doped transparent glass-ceramic containing nano-Ca5(PO4)3F (FAP) was prepared in reducing atmosphere. XRD and TEM analysis indicated that nano-FAP about 40 nm precipitated homogeneously in glass matrix after heat treatment. Confirmed by spectroscopy measurements, the crystal-like absorption and emission of Eu(2+) indicated the partition of Eu(2+) into FAP nanocrystals in glass ceramic. NIR emission due to the transition (2)F5/2?(2)F7/2 of Yb(3+) ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu(2+) to Yb(3+), which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu(2+)-Yb(3+) co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells. PMID:23816484

Li, Chen; Song, Zhiguo; Li, Yongjin; Lou, Kai; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Wang, Xue; Wang, Qi; Wan, Ronghua

2013-10-01

74

Upconversion color tunability and white light generation in Tm 3+/Ho 3+/Yb 3+ doped aluminum germanate glasses  

NASA Astrophysics Data System (ADS)

Tm 3+/Ho 3+/Yb 3+ triply doped aluminum germanate glasses exhibiting multicolor upconversion fluorescences have been fabricated and characterized. Efficient three-photon blue upconversion emission of Tm 3+ and two-photon green and red upconversion fluorescences of Ho 3+ have been observed. The strong red emission of Ho 3+, which is more than eight times higher than that of the green emission, is desirable in achieving high color rendering index. By varying the excitation power of the 974 nm wavelength laser diode, a series of white fluorescences with a large range of correlated color temperature ( CCT) was obtained, and the fluorescence colors can be tuned from yellowish white to warm white, pure white, cool white, and bluish white with different CCT. The upconversion color tunability via pump power adjustment will promote the development of three-dimensional solid-state displays and upconversion illumination devices.

Gong, Hua; Yang, Dianlai; Zhao, Xin; Yun Bun Pun, Edwin; Lin, Hai

2010-02-01

75

Investigation of A=155 and A=151 nuclides: Identification of the 155Tm s1\\/2 isomer and of the 155Yb beta-decay branch  

Microsoft Academic Search

The decay properties of 155Lu, 155Yb, 155Tm, and of the alpha-decay daughters 151Er and 151Ho were investigated following the on-line mass separation of A=155 nuclides produced in 64Zn irradiations of 95Mo. In the study, the half-life of the low-spin isomer in 155Lu was measured to be 140+\\/-20 ms, the beta-decay branch of 155Yb was identified by observing daughter gamma rays

K. S. Toth; K. S. Vierinen; M. O. Kortelahti; D. C. Sousa; J. M. Nitschke; P. A. Wilmarth

1991-01-01

76

Enhancement of near-infrared to near-infrared upconversion emission in the CeO?: Er³?, Tm³?, Yb³? inverse opals.  

PubMed

In this Letter, CeO?: Er³?, Tm³?, Yb³? inverse opal with near-infrared to near-infrared upconversion emission was prepared by polystyrene colloidal crystal templates, and the influence of photonic bandgap on the upconversion emission was investigated. Comparing with the reference sample, suppression of the blue or red upconversion luminescence was observed in the inverse opals. It is interesting that the near-infrared upconversion emission located at about 803 nm was enhanced due to the inhibition of visible upconversion emission in the inverse opals. Additionally, the variety of upconversion emission mechanisms was observed and discussed in the CeO?: Er³?, Tm³?, Yb³? inverse opals. PMID:24562241

Wu, Hangjun; Yang, Zhengwen; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo; Yang, Yong; Zhou, Dacheng

2014-02-15

77

Upconversion emission enhancement in silica-coated Gd 2O 3:Tm 3+, Yb 3+ nanocrystals by incorporation of Li + ion  

Microsoft Academic Search

Silica-coated Tm3+, Yb3+, Li+-tridoped Gd2O3 nanocrystals (GTYLS) were prepared by a reverse microemulsion method. The blue upconversion luminescence intensity of this nanocomposite was enhanced remarkably by the incorporation of Li+ ions as compared with that of lithium-free Gd2O3:Tm3+, Yb3+@SiO2 (GTYS) nanocomposites. X-ray diffraction patterns (XRD) of GTYS and GTYLS revealed that Gd2O3 were cubic, silica shell was noncrystalline. The transmission

Qiu Sun; Hua Zhao; Xiangqun Chen; Fuping Wang; Wei Cai; Zhaohua Jiang

2010-01-01

78

Thermal decomposition of Ln(C 2 H 5 CO 2 ) 3 ·H 2 O (Ln = Ho, Er, Tm and Yb)  

Microsoft Academic Search

The thermal decomposition of Ho(III), Er(III), Tm(III) and Yb(III) propionate monohydrates in argon was studied by means of\\u000a thermogravimetry (TG), differential thermal analysis (DTA), IR-spectroscopy and X-ray diffraction (XRD). Dehydration takes\\u000a place around 90 °C. It is followed by the decomposition of the anhydrous propionates to Ln2O2CO3 (Ln = Ho, Er, Tm or Yb) with the evolution of CO2 and 3-pentanone (C2H5COC2H5) between

J.-C. Grivel

79

M"ossbauer Study of Eu14MnSb11 and Yb14MnSb11 Zintl Compounds.  

NASA Astrophysics Data System (ADS)

Antimony-121 M"ossbauer effect measurements have been performed mainly on Eu14MnSb11 and Yb14MnSb11 zintl compounds, through the temperature range from 2 K to room temperature. The isomer shifts observed (-4.5mm/sec to --10.3 mm/sec and -7.7 mm/sec to --11.2 mm/sec, respectively) from the present study for both Eu14MnSb11 and Yb14MnSb11 zintl compounds are close to the values (-8.54mm/sec to --8.73mm/sec) obtained for InSb, the standard compound for antimony-121 M"ossbauer effect measurements. Isomer shift distribution fits by using a Voigt-based Gaussian distribution profile show distinct peaks at the corresponding average isomer shift values obtained from Lorentzian four-site fits for Eu14MnSb11. The study of the temperature dependence of line broadening as well as hyperfine magnetic field confirms the existence of long-range magnetic ordering of antimony-121 in Eu14MnSb11 below 12 K which resulted in the transition temperature, TC, of 12 K, whereas TC found in Yb14MnSb11 is 45 K. The linear fit of the natural logarithm of area versus temperature using the Debye model for the high-temperature limit gives the values of 185 K and 196 K for the Debye temperature for Eu14MnSb11 and Yb14MnSb11 zintl compounds, respectively.

Kafle, Durga; Brown, Dennis

2006-05-01

80

White up-conversion emission in Ho 3+/Tm 3+/Yb 3+ tri-doped glass ceramics embedding BaF 2 nanocrystals  

NASA Astrophysics Data System (ADS)

Ho 3+/Tm 3+/Yb 3+ tri-doped glass ceramics with white light emitting have been developed and demonstrated. Pumped by 980 nm laser diode (LD), intensive red, green and blue up-conversions (UC) were obtained. The green emission is assigned to Ho 3+ ion and the blue emission is assigned to Tm 3+ ion, whereas the red emission is the combination contribution of the Ho 3+ and Tm 3+ ions. The RGB intensities could be adjusted by tuning the rare-earth ion concentration and pump power intensity. Thus, multicolor of the luminescence, including perfect white light with CIE- X=0.329 and CIE- Y=0.342 in the 1931 CIE chromaticity diagram can be obtained in 0.15 Ho 3+/0.2Tm 3+/3Yb 3+ tri-doped glass ceramics embedding BaF 2 nanocrystals pumped by a single infrared laser diode source of 980 nm at 500 mW. The up-conversion luminescence mechanism of Yb 3+ sensitize Ho 3+ and Tm 3+ ions and the energy transfer from Ho 3+ to Tm 3+ in oxy-fluoride silicate glass ceramics were analyzed.

Li, Chenxia; Xu, Shiqing; Ye, Rengguang; Deng, Degang; Hua, Youjie; Zhao, Shilong; Zhuang, Songlin

2011-04-01

81

Charge-transfer bands in crystals of alkaline earth fluorides with Eu3+ and Yb3 + 1  

Microsoft Academic Search

The absorption, luminescence, and excitation spectra of CaF2, SrF2, and BaF2 crystals with EuF3 or YbF3 impurity have been investigated in the range 1 12 eV. In all cases, strong wide absorption bands (denoted as CT1) were observed at energies below the 4 f n -4 f n - 15 d absorption threshold of impurity ions. Weaker absorption bands (denoted

E. A. Radzhabov; A. I. Nepomnyashchikh; V. Kozlovskii

2008-01-01

82

Valency states of Yb, Eu, Dy and Ti ions in Li 2B 4O 7 glasses  

NASA Astrophysics Data System (ADS)

Absorption and emission spectra of Eu and Dy, Yb and Ti ions in Li 2B 4O 7 glasses grown in oxygen and hydrogen gas atmospheres were measured for valency states and lattice-sites analysis. For the Li 2B 4O 7 glass doped with Eu 2+, Eu 3+ and Dy 3+ ions which were grown in oxidizing and reducing atmospheres, absorption and emission bands due to these ions were investigated before and after ?-irradiation. For the Yb 3+-doped Li 2B 4O 7 glass, a weak, broad band was observed near the sharp 976.3 nm absorption band. The origin of this band is discussed in comparison with other glasses. Moreover, irradiation experiments using ?-rays were also performed in order to investigate the possibility of valency change of Yb ions. It was found that Ti 4+ ions, which are produced under oxidizing atmosphere, change to Ti 3+ ions after ?-irradiation with a dose of 10 5 Gy. An additional absorption band observed at about ˜500 nm is due to the Ti 3+ ions accompanied by charge-compensating vacancy and does not give any emission.

Kaczmarek, S?awomir M.; Tsuboi, Taiju; Boulon, Georges

2003-06-01

83

Observation of multi-mode: Upconversion, downshifting and quantum-cutting emission in Tm3+/Yb3+ co-doped Y2O3 phosphor  

NASA Astrophysics Data System (ADS)

Micro-crystalline Y2O3 phosphor co-doped with Yb3+/Tm3+ has been synthesized and characterized. The phosphor material gives efficient multimodal emission via downshifting (DS), upconversion (UC), and downconversion (DC)/quantum cutting (QC) luminescence processes. Cross relaxation and co-operative energy transfer (CET) have been ascribed as the possible mechanism for QC; as result of which a UV/blue photon absorbed by Tm3+ splits into two near infrared photons (wavelength range 950-1050 nm) emitted by Yb3+. The Yb3+ concentration dependent ET efficiency and QC efficiency has also been evaluated. Such multi-mode emitting phosphors could have potential applications in increasing the conversion efficiency of solar cells via spectral modification.

Yadav, Ranvijay; Singh, S. K.; Verma, R. K.; Rai, S. B.

2014-04-01

84

Doxorubicin conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles for therapy and sensing of drug delivery by luminescence resonance energy transfer.  

PubMed

In this study, we report an anticancer drug delivery system based on doxorubicin (DOX)-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles. The as-synthesized nanoparticles consist of uniform spherical nanoparticles with an average diameter of 25 nm. The drug delivery system demonstrates the ability to release DOX by cleavage of the hydrazone bond in mildly acidic environments. The spectra overlap between emission of donor NaYF(4):Yb(3+)/Tm(3+) nanoparticles at 452 nm ((1)D(2)?(3)F(4)) and 477 nm ((1)G(4)?(3)H(6)) and the broad absorbance of acceptor DOX centered at around 480 nm enables energy transfer to occur between the nanoparticles and DOX. The quenching and recovery of the up-conversion luminescence of NaYF(4):Yb(3+)/Tm(3+) by DOX due to luminescence resonance energy transfer (LRET) mechanism are applied as optical probe to confirm the DOX conjunction and monitor the release of DOX. The DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles exhibit an obvious cytotoxic effect on SKOV3 ovarian cancer cells via MTT assay. Meanwhile, the endocytosis process of DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles by SKVO3 cells was demonstrated through confocal laser scanning microscopy (CLSM), flow cytometry and ICP-OES. Such drug delivery system, which combines pH-triggered drug-release and up-converting nanoparticles-based LRET property, has excellent potential applications in cancer therapy and smart imaging. PMID:22938822

Dai, Yunlu; Yang, Dongmei; Ma, Ping'an; Kang, Xiaojiao; Zhang, Xiao; Li, Chunxia; Hou, Zhiyao; Cheng, Ziyong; Lin, Jun

2012-11-01

85

Intense blue up-conversion luminescence in Tm3+/Yb3+ codoped oxyfluoride glass-ceramics containing beta-PbF2 nanocrystals.  

PubMed

Up-conversion luminescence properties of a Tm3+/Yb3+ codoped oxyfluoride glass-ceramics under 980 nm excitation are investigated. Intense blue emission centered at 476 nm, corresponding to 1G4-->3H6 transitions of Tm3+ was simultaneously observed in the transparent oxyfluoride glass ceramics at room temperature. The intensity of the blue up-conversion luminescence in a 1 mol% YbF3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The reason for the intense Tm3+ up-conversion luminescence in the oxyfluoride glass-ceramics is discussed. The dependence of up-conversion intensities on excitation power and possible up-conversion mechanism are also evaluated. PMID:16095958

Zhang, Junjie; Duan, Zhongchao; He, Dongbing; Dai, Shixun; Zhang, Liyan; Hu, Lili

2005-12-01

86

Mechanisms and concentrations dependence of up-conversion luminescence in Tm^3^+/Yb^3^+ codoped oxyfluoride glass-ceramics [rapid communication  

NASA Astrophysics Data System (ADS)

The up-conversion properties of Tm3+/Yb3+ codoped oxyfluoride glass-ceramics under 980 nm excitation were investigated. Intense blue up-conversion luminescence due to the Tm3+: 1G4 ? 3H6 transition was observed in the glass-ceramics. The intensity of the blue up-conversion luminescence in a 1 mol% YbF3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The up-conversion mechanism is proposed. The reason for the intense Tm3+ up-conversion luminescence in the oxyfluoride glass-ceramics and the concentrations dependence of upconversion luminescence are also discussed.

Zhang, Junjie; He, Dongbing; Duan, Zhongchao; Zhang, Liyan; Dai, Shixun; Hu, Lili

2005-04-01

87

Li+ ion doping: an approach for improving the crystallinity and upconversion emissions of NaYF4:Yb3+, Tm3+ nanoparticles.  

PubMed

The application of upconversion nanoparticles (UCNPs), especially in vivo, has so far been hampered by their relatively low upconversion efficiency. In this work, a strategy of Li(+) doping was revisited with the aim of enhancing UV to blue UC luminescence of NaYF4:Yb(3+), Tm(3+) nanocrystals. We have demonstrated that the short wavelength UC emission bands were indeed significantly enhanced. Compared to lithium-free NaYF4:Yb(3+), Tm(3+), the UC emission intensities of 452 nm and 479 nm of the NPs co-doped with 7 mol% Li(+) ions were increased by 8 and 5 times, respectively. The mechanism of the enhancement was discussed and the improvement of the nanoparticles' crystallinity and the distortion of the local symmetry around the Tm(3+) ions, when the Li(+) ions were introduced, were confirmed to be the origin of the improvement. PMID:23877262

Zhao, Chengzhou; Kong, Xianggui; Liu, Xiaomin; Tu, Langping; Wu, Fei; Zhang, Youlin; Liu, Kai; Zeng, Qinghui; Zhang, Hong

2013-09-01

88

Nanocrystals precipitation and up-conversion luminescence in Yb 3+Tm 3+ co-doped oxyfluoride glasses  

Microsoft Academic Search

Rare earth ions doped oxyfluoride glass with composition of 28SiO2·22AlO1.5·40PbF2·10PbO·(4.8–x) GdF3·0.1NdF3·xYbF3·0.1TmF3 (x=0, 0.1, 0.2, 0.5, 1, 2, 3, 4 and 4.8) in molar ratio was developed. When the oxyfluoride glasses were heat-treated at the first crystallization temperature, the glasses gave transparent glass-ceramics in which rare earth containing fluorite-type nanocrystals of about 17.2 nm in diameter uniformly precipitated in the glass

Jianbei QIU; Zhiguo SONG

2008-01-01

89

Crystal structures of lanthanide and zirconium phosphates with general formula Ln {sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3}, where Ln=Ce, Eu, Yb  

SciTech Connect

Crystal structures of synthetic phosphates Ce{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3}, Eu{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} and Yb{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} have been refined by Rietveld method using powder diffraction data. Unit cell parameters: a=8.7419 (4), c=23.128 (2) A; a=8.7659 (1), c=22.822 (1) A; a=8.8078 (4), c=22.485 (3) A, respectively; Z=6. Values of final R-factors in isotropic approximation: R {sub wp}=4.00, R {sub wp}=3.33, R {sub wp}=4.12%, respectively. New space group P3-barc has been established for the compounds with general formula Ln {sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3}, where Ln=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y. It has been confirmed that the synthetic phosphates with general formula Ln {sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} belong to the NZP (sodium zirconium phosphate) structure type. - Graphical abstract: Fragment of structure of synthetic phosphate Eu{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3}.

Bykov, D.M. [Chemical Department, Nizhny Novgorod State University, Nizhny Novgorod 603950 (Russian Federation); Gobechiya, E.R. [Geological Department, Moscow State University, Moscow 119992 (Russian Federation); Kabalov, Yu.K. [Geological Department, Moscow State University, Moscow 119992 (Russian Federation); Orlova, A.I. [Chemical Department, Nizhny Novgorod State University, Nizhny Novgorod 603950 (Russian Federation)]. E-mail: oai@uic.nnov.ru; Tomilin, S.V. [Waste Immobilization Laboratory, Chemical and Technological Department, Research Institute of Atomic Reactors, Dimitrovgrad - 10, Ulyanovsk region 433510 (Russian Federation)

2006-10-15

90

Charge-transfer bands in crystals of alkaline earth fluorides with Eu3+ and Yb3 + 1  

NASA Astrophysics Data System (ADS)

The absorption, luminescence, and excitation spectra of CaF2, SrF2, and BaF2 crystals with EuF3 or YbF3 impurity have been investigated in the range 1 12 eV. In all cases, strong wide absorption bands (denoted as CT1) were observed at energies below the 4 f n -4 f n - 15 d absorption threshold of impurity ions. Weaker absorption bands (denoted as CT2) with energies 1.5 2 eV lower than those of the CT1 bands have been found in the spectra of CaF2 and SrF2 crystals with EuF3 or YbF3 impurities. The fine structure of the luminescence spectra of CaF2 crystals with EuF3 impurities has been investigated under excitation in the CT bands. Under excitation in the CT1 band, several Eu centers were observed in the following luminescence spectra: C 4 v , O h , and R aggregates. Excitation in the CT2 bands revealed luminescence of only C 4 v defects.

Radzhabov, E. A.; Nepomnyashchikh, A. I.; Kozlovski?, V.

2008-09-01

91

Colour emission tunability in Ho3+-Tm3+-Yb3+ co-doped Y2O3 upconverted phosphor  

NASA Astrophysics Data System (ADS)

The frequency upconversion (UC) emission throughout the visible region from the Y2O3:Ho3+-Tm3+-Yb3+ co-doped phosphors synthesized by using low temperature combustion process upon excitation with a diode laser operating at 980 nm have been presented. The colour emission tunability in co-doped phosphor has been observed on increasing the pump power and seen by the naked eyes. The tunability in colour emission has also been visualized by CIE chromaticity diagram. The variation in UC emission intensity of the 1G4 ? 3H6 (Tm3+) and 5F3 ? 5I8 (Ho3+) transitions lying in the blue region has been monitored with increase in the pump power and marked that their ratio can be used to determine the temperature. The developed phosphor has been used to record fingerprints. The observed most intense visible colour emission from the developed material may be used for photodynamic therapy and as an alternative of traditional fluorescent biolabels.

Pandey, Anurag; Rai, Vineet Kumar

2012-12-01

92

Synthesis, structure, magnetism, and optical properties of theordered mixed-lanthanide sulfides gamma-LnLn'S3 (Ln=La, Ce; Ln'=Er, Tm,Yb)  

SciTech Connect

{gamma}-LnLn{prime}S{sub 3} (Ln = La, Ce; Ln{prime} = Er, Tm, Yb) have been prepared as dark red to black single crystals by the reaction of the respective lanthanides with sulfur in a Sb{sub 2}S{sub 3} flux at 1000 C. This isotypic series of compounds adopts a layered structure that consists of the smaller lanthanides (Er, Tm, and Yb) bound by sulfide in six- and seven-coordinate environments that are connected together by the larger lanthanides (La and Ce) in eight- and nine-coordinate environments. The layers can be broken down into three distinct one-dimensional substructures containing three crystallographically unique Ln{prime} centers. The first of these is constructed from one-dimensional chains of edge-sharing [Ln{prime}S{sub 7}] monocapped trigonal prisms that are joined to equivalent chains via edge-sharing to yield ribbons. There are parallel chains of [Ln{prime}S{sub 6}] distorted octahedra that are linked to the first ribbons through corner-sharing. These latter units also share corners with a one-dimensional ribbon composed of parallel chains of [Ln{prime}S{sub 6}] polyhedra that edge-share both in the direction of chain propagation and with adjacent identical chains. Magnetic susceptibility measurements show Curie-Weiss behavior from 2 to 300 K with antiferromagnetic coupling, and no evidence for magnetic ordering. The {theta}{sub p} values range from -0.4 to -37.5 K, and spin-frustration may be indicated for the Yb-containing compounds. All compounds show magnetic moments substantially reduced from those calculated for the free ions. The optical band gaps for {gamma}-LaLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.6 eV, whereas {gamma}-CeLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.3 eV.

Jin, G.B.; Choi, E.S.; Guertin, R.P.; Brooks, J.S.; Bray, T.H.; Booth, C.H.; Albrecht-Schmitt, T.E.

2006-12-12

93

Anomalous Hall effect in three ferromagnetic compounds: EuFe4Sb12 , Yb14MnSb11 , and Eu8Ga16Ge30  

NASA Astrophysics Data System (ADS)

The Hall resistivity (?xy) , resistivity (?xx) , and magnetization of three metallic ferromagnets are investigated as a function of magnetic field and temperature. The three ferromagnets, EuFe4Sb12 (Tc?84K) , Yb14MnSb11 (Tc?53K) , and Eu8Ga16Ge30 (Tc?36K) are Zintl compounds with carrier concentrations between 1×1021 and 3.5×1021cm-3 . The relative decrease in ?xx below Tc [?xx(Tc)/?xx(2K)] is 28, 6.5, and 1.3 for EuFe4Sb12 , Yb14MnSb11 , and Eu8Ga16Ge30 , respectively. The low carrier concentrations coupled with low magnetic anisotropies allow a relatively clean separation between the anomalous (?xy') , and normal contributions to the measured Hall resistivity. For each compound the anomalous contribution in the zero field limit is fit to a?xx+?xy?xx2 for temperatures TEuFe4Sb12 , Yb14MnSb11 , and Eu8Ga16Ge30 , respectively, and is independent of temperature for T

Sales, Brian C.; Jin, Rongying; Mandrus, David; Khalifah, Peter

2006-06-01

94

Heterometallic Na-Y(Ln) trifluoroacetate diglyme complexes as novel single-source precursors for upconverting NaYF4 nanocrystals co-doped with Yb and Er/Tm ions.  

PubMed

We report synthesis of new single-source heterometallic precursors [NaLn(TFA)(4)(diglyme)] (Ln = Y, Er, Tm, Yb; TFA = trifluoroacetate), which decompose in 1-octadecene at significantly low temperature, without using any surfactant or capping reagent, to give sub-50 nm particles of cubic and/or hexagonal NaYF(4) : Yb(3+), Er(3+)/Tm(3+) materials forming well-dispersed colloidal solutions in dichloromethane and exhibiting green/blue upconversion luminescence. PMID:20401365

Mishra, Shashank; Daniele, Stéphane; Ledoux, Gilles; Jeanneau, Erwann; Joubert, Marie-France

2010-06-01

95

Charge-transfer bands in crystals of alkaline earth fluorides with Eu 3+ and Yb 3 + 1  

Microsoft Academic Search

The absorption, luminescence, and excitation spectra of CaF2, SrF2, and BaF2 crystals with EuF3 or YbF3 impurity have been investigated in the range 1–12 eV. In all cases, strong wide absorption bands (denoted as CT1) were observed at energies below the 4f\\u000a \\u000a n\\u000a -4f\\u000a \\u000a n ? 15d absorption threshold of impurity ions. Weaker absorption bands (denoted as CT2) with energies

E. A. Radzhabov; A. I. Nepomnyashchikh; V. Kozlovski?

2008-01-01

96

A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals.  

PubMed

The spectroscopic behavior of gadolinium gallium garnet (Gd3Ga5O12, GGG) nanocrystals codoped with 1% each of Tm3+ and Yb3+ prepared via a solution combustion synthesis procedure was investigated. Initial excitation of the codoped nanocrystals with 465.8 nm (into the 1G4 state) showed a dominant blue-green emission ascribed to the 1G4-3H6 transition as well as red and NIR emissions from the 1G4-3F4 and 1G4-3H5/3H4-3H6 transitions, respectively. Excitation at this wavelength (465.8 nm) showed the existence of a Tm3+ --> Yb3+ energy transfer process evidenced by the presence of the 2F5/2-2F7/2 Yb3+ emission in the NIR emission spectrum. The decay time constants proved that the transfer of energy occurred via the 3H4 state. Following excitation of the Yb3+ ion with 980 nm, intense upconverted emission was observed. Emissions in the UV (1D2-3H6), blue (1D2-3F4), blue-green (1G4-3H6), red (1G4-3F4), and NIR (1G4-3H5/3H4-3H6) were observed and were the direct result of subsequent transfers of energy from the Yb3+ ion to the Tm3+ ion. Power dependence studies showed a deviation from expected values for the number of photons involved in the upconversion thus indicating a saturation of the upconversion process. An energy transfer efficiency of 0.576 was determined experimentally. PMID:16853224

Pandozzi, Fabiano; Vetrone, Fiorenzo; Boyer, John-Christopher; Naccache, Rafik; Capobianco, John A; Speghini, Adolfo; Bettinelli, Marco

2005-09-22

97

Spectroscopy of Yb:Tm doped tellurite glasses for efficient infrared fiber laser  

NASA Astrophysics Data System (ADS)

We performed extensive spectroscopy of tellurite glasses doped with high concentration of Tm ions for laser emission at around 2 micron wavelength. The aim of the work is to develop a glass suitable for single-frequency fiber laser. In fact such a kind of laser require the use of short cavity length and therefore high gain per unit length medium. Tellurite glasses allows high-doping concentration and are therefore an excellent candidate. In these paper we review our recent results. In particular we address the optical and thermo-mechanical properties of several tellurite glasses (75mol%Te02.20mol%ZnO. 5mol%Na2O) with Tm3+ doping up to 111,564 ppm.

Gebavi, H.; Taher, M.; Lousteau, J.; Milanese, D.; Taccheo, S.; Schulzgen, A.; Ferraris, M.; Peyghambarian, N.

2010-02-01

98

Experimental study on the surface modification of Y2O3:Tm3+\\/Yb3+ nanoparticles to enhance upconversion fluorescence and weaken aggregation  

Microsoft Academic Search

In order to improve the solubility of doped nanoparticles in solutions, Y2O3:Tm3+\\/Yb3+ nanoparticles were synthesized using the Pechini-type sol-gel method, and their surfaces were modified with amino or carboxylic functional groups using ligand-capped and ligand-exchanging methods. The nanoparticles with modified surfaces were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and zeta potential (zeta), and their photoluminescence

Qiang Lü; Ai Hua Li; Feng Yun Guo; Liang Sun; Lian Cheng Zhao

2008-01-01

99

CW and Q-switched 2.1 ?m Tm3+/Ho3+/Yb3+-triply-doped tellurite fibre lasers  

NASA Astrophysics Data System (ADS)

We present efficient CW lasing Tm3+/Ho3+/Yb3+-triply-doped tellurite fibre at ~2.1 ?m. Two different pump schemes have been demonstrated for this laser: a 1.088 ?m Yb3+-doped silica fibre laser simultaneously pumping the Tm3+: 3H5, Ho3+: 5I6 and Yb3+: 2F5/2 levels, and a 1.6 ?m Er3+/Yb3+-doped silica fibre laser directly pumping the Tm3+: 3F4 level. For the 1.6 ?m pumping, a slope efficiency of 62% has been achieved in a 76 cm long fibre which is close to the Stokes efficiency limit of ~75%. An output power of 160 mW has also been achieved, but with no signs of saturation or fibre damage suggesting that higher output powers should be possible. For the 1.088 ?m pumping there is very strong pump ESA resulting in bright blue (480 nm) and near-IR (800 nm) fluorescence due to the 1G4 --> 3H6 and 3H4 --> 3H6 transitions of Tm3+, respectively, and this limits the achievable slope efficiency, which in this case was a maximum of 25% for a 17 cm long fibre. With this pump scheme, the highest observed output power was 60 mW, and further power scaling was limited due to the intense ESA and thermal damage to the pump end of the fibre. We also present results on the active Q-switching of the 1.6 ?m pumped fibre laser using a mechanical chopper operating at 19.4 kHz. Average powers of 26 mW and pulse energies of 0.65 ?J were measured with pulse widths in the range 100-160 ns.

Richards, Billy D. O.; Tsang, Yuen H.; Binks, David J.; Lousteau, Joris; Jha, Animesh

2008-10-01

100

Tuning upconversion luminescence of LiYF4:Yb3+,Er3+/Tm3+/Ho3+ microcrystals synthesized through a molten salt process.  

PubMed

In this paper, well-defined tetragonal-phase LiYF4:Yb3+,Er3+/Tm3+/Ho3+ micro-crystals with octahedral morphology were successfully prepared through a surfactant-free molten salt process for the first time. By gradually increasing the LiF content in the NaNO3-KNO3 reaction medium, the crystal phase transforms from a mixture of YF3 and LiYF4 to pure tetragonal-phase LiYF4. The possible formation process for the phase and morphology evolution is also presented. Moreover, upon 980 nm laser diode (LD) excitation, the lanthanide ions (Yb3+, Er3+/Tm3+/Ho3+) doped LiYF4 crystals exhibit intense upconversion emission lights. By tuning the sensitizer concentrations of Yb3+ ions in LiYF4:Yb3+,Er3+, the relative intensities of green and red emissions can be precisely adjusted under single wavelength excitation. Consequently, multicolor upconversion emissions can be obtained. On the other hand, UC mechanisms were also given based on the emission spectra and the plot of luminescence intensity to pump power. PMID:24734579

Niu, Na; He, Fei; Wang, Liuzhen; Wang, Lin; Wang, Yan; Gai, Shili; Yang, Piaoping

2014-05-01

101

Graphene supported ?NaYF4:Yb3+,Tm3+ and N doped P25 nanocomposite as an advanced NIR and sunlight driven upconversion photocatalyst  

NASA Astrophysics Data System (ADS)

A new photocatalytic nanocomposite consisting of upconversion material (?-NaYF4:Yb3+,Tm3+), N doped P25 (P(N)), and graphene (GP) has been fabricated successfully and shown to be an advanced photocatalyst under the near infrared (NIR) and sunlight irradiation. During the preparation process, ?-NaYF4:Yb3+,Tm3+ and P(N) were simultaneously loaded on GP and they were closely attach to each other. The light absorption range of P(N) matches well with the converted light emission peaks of ?-NaYF4:Yb3+,Tm3+, resulting in P(N) can absorb the converted light sufficiently for photocatalysis. The introduced GP not only act as the support material, but also enhances the light absorption and photogenerated electron-hole pairs' separation. Photocatalytic activity measurements of the new photocatalyst under the NIR and simulated sunlight irradiation was improved compared with those of pure and GP supported P(N). The upconversion efficiency related photocatalytic activity confirms the significant role of upconversion materials. Overall, this investigation may provide new insights in preparing new photocatalysts by coupling with optical function materials to make sufficient use of sunlight for practical applications.

Wang, Wei; Huang, Wenjuan; Ni, Yaru; Lu, Chunhua; Tan, Lijuan; Xu, Zhongzi

2013-10-01

102

Specific features of magnetoresistance during the antiferromagnet-paramagnet transition in Tm{sub 1-x}Yb{sub x}B{sub 12}  

SciTech Connect

The transverse magnetoresistance {Delta}{rho}/{rho}(H, T) of Tm{sub 1-x}Yb{sub x}B{sub 12} single crystals is studied in the ytterbium concentration range corresponding to the antiferromagnet-paramagnet transition in a magnetic field up to 80 kOe at low temperatures. A magnetic H-T phase diagram is constructed for the antiferromagnetic state of substitutional Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions with x {<=} 0.1. The contributions to the magnetoresistance in the antiferromagnetic and paramagnetic phases of the dodecaborides under study are separated. Along with negative quadratic magnetoresistance -{Delta}{rho}/{rho} {proportional_to} H{sub 2}, the magnetically ordered phase of these compounds is found to have component {Delta}{rho}/{rho} {proportional_to} H that linearly changes in a magnetic field. The negative contribution to the magnetoresistance of Tm{sub 1-x}Yb{sub x}B{sub 12} is analyzed in terms of the Yosida model for a local magnetic susceptibility.

Sluchanko, N. E., E-mail: nes@lt.gpi.ru; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Levchenko, A. V.; Filippov, V. B.; Shitsevalova, N. Yu. [National Academy of Sciences of Ukraine, Institute of Problems of Materials Science (Ukraine)

2013-05-15

103

Plasmonic enhanced emissions from cubic NaYF(4):Yb: Er/Tm nanophosphors.  

PubMed

A metal shell was used in this study to provide significant enhancement of the up-converted emission from cubic NaYF(4) nanoparticles, creating a valuable composite material for labeling in biology and other applications - use of the cubic form of the material obviates the need to undertake a high temperature transformation to the naturally more efficient hexagonal phase. The NaYF(4) matrix contained ytterbium sensitizer and an Erbium (Er) or Thulium (Tm) activator. The particle sizes of the as-synthesized nanoparticles were in the range of 20-40 nm with a gold shell thickness of 4-8 nm. The gold shell was macroscopically amorphous. The synthesis method was based on a citrate chelation. In this approach, we exploited the ability of the citrate ion to act as a reductant and stabilizer. Confining the citrate ion reductant on the nanophosphor surface rather than in the solution was critical to the gold shell formation. The plasmonic shell enhanced the up-conversion emission of Tm from visible and near-infrared regions by up to a factor of 8, in addition to imparting a visible color arising from the plasmon absorption of the gold shell. The up-conversion enhancement observed with Tm and Er were different for similar gold coverages, with local crystal field changes as a possible route to enhance up-conversion emission from high symmetry structural hosts. These novel up-converting nanophosphor particles combine the phosphor and features of a gold shell, providing a unique platform for many biological imaging and labeling applications. PMID:21709812

Sudheendra, L; Ortalan, Volkan; Dey, Sanchita; Browning, Nigel D; Kennedy, I M

2011-06-14

104

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method  

NASA Astrophysics Data System (ADS)

Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from 2H11/2 --> 2I15/2 and 4S3/2 --> 4I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K-1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers.

Gavrilovi?, Tamara V.; Jovanovi?, Dragana J.; Lojpur, Vesna; Drami?anin, Miroslav D.

2014-02-01

105

Yellow-orange upconversion emission in Eu(3+)-Yb(3+) codoped BaTiO(3) phosphor.  

PubMed

The Eu(3+)-Yb(3+) codoped BaTiO3 phosphor is prepared via co-precipitation method and its upconversion emission is studied by 980nm diode laser excitation. The X-ray diffraction pattern of the prepared sample showed the tetragonal BaTiO3 phase. The co-doped phosphor showed sharp upconversion emission bands peaking at ?592, ?614, ? 654, ?704 and ?796nm due to the (5)D0?(7)F1, (5)D0?(7)F2, (5)D0?(7)F3, (5)D0?(7)F4 and (5)D0?(7)F6 transitions, respectively of Eu(3+) ions. The sharp band at 489nm is assigned to the (2)F5/2?(2)F7/2 transition of Yb(3+) ion while the broad band around 505nm is assigned to the defect states present in the sample. Based on the available experimental data, the process involved in the UC emissions has been explored and elaborated. PMID:24632162

Kumari, Astha; Rai, Vineet Kumar; Kumar, Kaushal

2014-06-01

106

Yellow-orange upconversion emission in Eu3+-Yb3+ codoped BaTiO3 phosphor  

NASA Astrophysics Data System (ADS)

The Eu3+-Yb3+ codoped BaTiO3 phosphor is prepared via co-precipitation method and its upconversion emission is studied by 980 nm diode laser excitation. The X-ray diffraction pattern of the prepared sample showed the tetragonal BaTiO3 phase. The co-doped phosphor showed sharp upconversion emission bands peaking at ?592, ?614, ? 654, ?704 and ?796 nm due to the 5D0 ? 7F1, 5D0 ? 7F2, 5D0 ? 7F3, 5D0 ? 7F4 and 5D0 ? 7F6 transitions, respectively of Eu3+ ions. The sharp band at 489 nm is assigned to the 2F5/2 ? 2F7/2 transition of Yb3+ ion while the broad band around 505 nm is assigned to the defect states present in the sample. Based on the available experimental data, the process involved in the UC emissions has been explored and elaborated.

Kumari, Astha; Rai, Vineet Kumar; Kumar, Kaushal

2014-06-01

107

Cross-relaxation induced tunable emissions from the Tm(3+)/Er(3+)/Eu(3+) ions activated BaGd2O4 nanoneedles.  

PubMed

Tm(3+), Er(3+), Tm(3+)/Er(3+), Tm(3+)/Er(3+)/Eu(3+) single, double and triple activator ion/ions doped nanocrystalline BaGd2O4 (BG) phosphors were prepared by a Pechini type sol-gel process. After annealing at 1300 °C, X-ray diffraction patterns confirmed their orthorhombic structure. Field-emission transmission electron microscope images of the BG sample indicated a nanoneedle-type morphology. Photoluminescence (PL) and cathodoluminescence (CL) measurements were utilized to establish the emission properties of rare-earth ions doped nanocrystalline BG host lattice. Under near-ultraviolet (NUV) excitations, BG:Tm(3+) and BG:Er(3+) exhibited their characteristic emissions in the blue and green regions, respectively, while BG:Tm(3+)/Er(3+) and BG:Tm(3+)/Er(3+)/Eu(3+) showed cyan and white light emissions, respectively, when doped with appropriate amounts of activator ions. In the PL, the cross-relaxation process is dominant rather than the energy transfer process. Due to the different mechanism from PL, the CL spectra showed different emission features of BG:Tm(3+)/Er(3+)/Eu(3+) phosphor. The CL spectra of BG:Tm(3+) and BG:Er(3+) established the high purity blue and green emissions, respectively. From the PL and CL investigations, the white-light emission was realized from the single-phase BG:Tm(3+)/Er(3+)/Eu(3+) phosphor under NUV and low voltage electron beam excitations. PMID:24846293

Seeta Rama Raju, G; Pavitra, E; Yu, Jae Su

2014-06-01

108

Luminescence properties of Tb3+, Eu3+, Tm3+ co-doped Na5La(MoO4)4 for white light-emitting diode.  

PubMed

Tb3+, Eu3+, Tm3+ co-doped Na5La(MoO4)4 phosphors were prepared by the conventional solid-state reaction. Under the excitation of UV light, Na5La(MoO4)4:Tm3+, Na5La(MoO4)4:Tb3+, and Na5La(MoO4)4:Eu3+ exhibit the characteristic emissions of Tm3+ (1D2 --> 3F4, blue), Tb3+ (5D4 --> 7F5, green), and Eu3+ (5D0 --> 7F2, red), respectively. By adjusting the doping concentration of rare earth ions in Na5La(MoO4)4:a Tm3+, b Tb3+, c Eu3+, a white emission in a single composition was obtained under the excitation of 362 nm. It might be a promising phosphor for the future applications. PMID:24734613

Jin, Ye; Lü, Wei; Zhang, Jiahua; Hao, Zhendong; Zhang, Xia

2014-05-01

109

Influence of Various Impurities on the Optical Properties of YbF3-Doped CaF2 Crystals  

NASA Astrophysics Data System (ADS)

Calcium fluoride crystals doped with YbF3 and co-doped with LiF and NaF were grown using the vertical Bridgman method. Several of rare-earth ions (such as Eu, Sm, Ho, Tm, and Yb) can be stabilized in the divalent state in the CaF2. The change of valence was attained by various methods. The optical absorption spectra reveal the characteristic absorption bands of the Yb3+ and Yb2+ ions. This means that the developed crystal growth process achieves a good Yb3+ to Yb2+ conversion in the as-grown crystals. The influence of other impurities, such as Na+ or Li+, on the absorption and emission spectrum of YbF3-doped CaF2 was studied. The Li+ and Na+ ions drastically decrease the absorption coefficient of the Yb2+ ions in the UV band and the emission intensity by excitation in 230 nm.

Stef, M.; Pruna, A.; Pecingina-Garjoaba, N.; Nicoara, I.

2007-11-01

110

Strongly enhancing photostimulated luminescence by doping Tm3+ in Sr3SiO5: Eu2+.  

PubMed

We report a large enhancement of yellow photostimulated luminescence (PSL) by codoping Tm3+ in Sr3SiO5:Eu2+ upon infrared stimulation at 980 nm after pre-exposure in Ultraviolet light. The initial PSL intensity and light storage capacity are enhanced by a factor of 33 and 2, respectively, for Tm3+ concentration at 0.0004. The thermoluminescence spectra indicate that codoping Tm3+ generates a trap peaking at 385 K. The trap is much more sensitive to infrared light than the original one, so that the light storage period of the material is beyond tens of days with the minimum detectable infrared power density only 54 ?W/cm2. PMID:23454944

Liu, Xia; Zhang, Jiahua; Zhang, Xia; Hao, Zhendong; Qiao, Jun; Dong, Xiaoling

2013-01-15

111

Novel heterometal-organic complexes as first single source precursors for up-converting NaY(Ln)F4 (Ln = Yb, Er, Tm) nanomaterials.  

PubMed

First heterometal-organic single source precursors for NaYF(4) nanomaterials as a host matrix for up-conversion emission are reported. These novel heterobimetallic derivatives NaY(TFA)(4)(diglyme) (1), [Na(triglyme)(2)][Y(2)(TFA)(7)(THF)(2)] (2) and Na(2)Y(TFA)(5)(tetraglyme) (3) (TFA = trifluoroacetate), which were fully characterized by elemental analysis, FT-IR and (1)H NMR spectroscopy, TG-DTA data as well as single crystal X-ray structures, are advantageous in terms of being anhydrous and having lower decomposition temperatures in comparison to the homometallic precursor Y(TFA)(3)(H(2)O)(3). In addition, they also contain chelating glyme ligands, which act as capping reagents during decomposition to control the NaYF(4) particle size and render them monodisperse in organic solvents. On decomposition in 1-octadecene, the molecular derivatives 1 and 3 are converted, in the absence of any surfactant or capping reagent, to cubic NaYF(4) nanocrystals at significantly lower temperatures (below 250 °C). At higher temperature, a mixture of the cubic and hexagonal phases was obtained, the relative ratio of the two phases depending on the reaction temperature. A pure hexagonal phase, which is many folds more efficient for UC emission than the cubic phase, was obtained by calcining nanocrystals of mixed phase at 400 °C. In order to co-dope this host matrix with up-converting lanthanide cations, analogous complexes NaLn(TFA)(4)(diglyme) [Ln = Er (4), Tm (5), Yb (6)] and Na(2)Ln(TFA)(5)(tetraglyme) [Ln = Er (7), Yb (8)] were also prepared and characterized. The decomposition in 1-octadecene of suitable combinations and appropriate molar ratios of these yttrium, ytterbium and erbium/thulium derivatives gave cubic and/or hexagonal NaYF(4): Yb(3+), Er(3+)/Tm(3+) nanocrystals (NCs) capped by diglyme or tetraglyme ligands, which were characterized by IR, TG-DTA data, EDX analysis and TEM studies. Surface modification of these NCs by ligand exchange reactions with poly acrylic acid (PAA) and polyethyleneglycol (PEG) diacid 600 was also carried out to render them water soluble. The THF solutions of suitable combinations of the diglyme derivatives were also used to elaborate the thin films of NaYF(4):Yb(3+), Er(3+)/Tm(3+) on a glass or Si wafer substrate by spin coating. The multicolour up-conversion fluorescence was successfully realized in the Yb(3+)/Er(3+) (green/red) and Yb(3+)/Tm(3+) (blue/violet) co-doped NaYF(4) nanoparticles and thin films, which demonstrates that they are promising UC nanophosphors of immense practical interest. The up-conversion excitation pathways for the Er(3+)/Yb(3+) and Tm(3+)/Yb(3+) co-doped materials are discussed. PMID:22134711

Mishra, Shashank; Ledoux, Gilles; Jeanneau, Erwann; Daniele, Stéphane; Joubert, Marie-France

2012-02-01

112

Stem Cell Labeling using Polyethylenimine Conjugated (?-NaYbF4:Tm3+)/CaF2 Upconversion Nanoparticles  

PubMed Central

We report on a polyethylenimine (PEI) covalently conjugated (?-NaYbF4:Tm3+)/CaF2 upconversion nanoparticle (PEI-UCNP) and its use for labeling rat mesenchymal stem cells (rMSCs). The PEI-UCNPs absorb and emit near-infrared light, allowing for improved in vivo imaging depth over conventional probes. We found that such covalent surface conjugation by PEI results in a much more stable PEI-UCNP suspension in PBS compared to conventional electrostatic layer by layer (LbL) self-assembling coating approach. We systematically examined the effects of nanoparticle dose and exposure time on rat mesenchymal stem cell (rMSC) cytotoxicity. The exocytosis of PEI-UCNPs from labeled rMSCs and the impact of PEI-UCNP uptake on rMSC differentiation was also investigated. Our data show that incubation of 100-µg/mL PEI-UCNPs with rMSCs for 4 h led to efficient labeling of the MSCs, and such a level of PEI-UCNP exposure imposed little cytotoxicity to rMSCs (95% viability). However, extended incubation of PEI-UCNPs at the 100 µg/mL dose for 24 hour resulted in some cytotoxicity to rMSCs (60% viability). PEI-UCNP labeled rMSCs also exhibited normal early proliferation, and the internalized PEI-UCNPs did not leak out to cause unintended labeling of adjacent cells during a 14-day transwell culture experiment. Finally, PEI-UCNP labeled rMSCs were able to undergo osteogenic and adipogenic differentiation upon in vitro induction, although the osteogenesis of labeled rMSCs appeared to be less potent than that of the unlabeled rMSCs. Taken together, PEI-UCNPs are promising agents for stem cell labeling and tracking.

Zhao, Liang; Kutikov, Artem; Shen, Jie; Duan, Chunying; Song, Jie; Han, Gang

2013-01-01

113

Investigation on up-conversion luminescence properties of novel transparent Ho3+-Tm3+-Yb3+ co-doped oxyfluoride glass ceramics  

NASA Astrophysics Data System (ADS)

In the present letter, the transparent oxyfluoride glass ceramics containing Ho3+-Tm3+-Yb3+:NaYF4 were successfully prepared by melt-quenching at 1400°C and subsequent heating at 650-680°C for 1~2 hours . X-ray diffraction (XRD) with Cu K? radiation (?=0.154nm) investigation revealed that NaYF4 nano-crystals in the glass ceramics was fabricated. Their sizes were determined by Sherrer's equation. The emission spectra red green and blue up-conversion (UC) under 980nm laser diode (LD) pumping and absorption spectra were measured. Luminescence measurements confirmed the partition of RE ions in nano-crystals NaYF4. The blue red and green UC radiations correspond to the transitions 1G4-3H6, 1G4-3H4 of Tm3+, 5F4, 5S2-5I8, 5F5-5I8, of Ho3+ ions, respectively. This is similar to that in Tm3+-Yb3+ and/or Ho3+-Yb3+ co-doped glass ceramics. To obtain upconversion fluorescence mechanisms, upconversion fluorescence intensity versus LD pump power were analyzed in view of energy levels of rare earth. Up-conversion mechanisms were discussed and the ratio between red, green and blue UC emission bands was found to be varied as a function of temperature of heat treatment and pump power. This result could be mainly attributed to the cross-relaxation between Ho3+ ions. The excellent optical properties and its convenient, low-cost synthesis of the present glass ceramic imply that it is an excellent substitution material for the unobtainable bulk NaYF4 crystal and may have potentially applications in tunable visible laser or many other fields.

Liu, Xiao-Bo; Han, Wan-Lei; Xu, Fang; Song, Ying-Lin

2011-06-01

114

Design, synthesis and characterization of an orange-yellow long persistent phosphor: Sr3Al2O5Cl2:Eu(2+),Tm(3+).  

PubMed

A novel orange-yellow emitting Sr3Al2O5Cl2:Eu(2+), Tm(3+) phosphor with bright and long persistent luminescence (LPL) has been newly developed. The incorporation of Tm(3+) into the Sr3Al2O5Cl2:Eu(2+) as an auxiliary activator dominates its long persistent luminescence and thermoluminescence characteristics to a large extent. The emissions in Sr3Al2O5Cl2:Eu(2+), Tm(3+) for both fluorescence and LPL are due to the 5d ? 4f transitions of Eu(2+). The orange-yellow long persistent luminescence with the chromaticity coordination of (0.53, 0.46) can persist for nearly 220 min at recognizable intensity level (? 0.32 mcd/m2). This investigation provides a new and efficient long persistent phosphor which enriches the color of the existing LPL. PMID:21164830

Li, Yanqin; Wang, Yuhua; Gong, Yu; Xu, Xuhui; Zhou, Meijiao

2010-11-22

115

Ultraviolet and blue up-conversion fluorescence of NaY 0.793? x Tm 0.007Yb 0.2Gd x F 4 phosphors  

Microsoft Academic Search

The NaY0.793?xTm0.007Yb0.2GdxF4 (x=0.1, 0.2, 0.3) phosphors were synthesized through a combinational method of co-precipitation and argon atmosphere annealing procedures. Crystallizations of the phosphors were characterized by X-ray diffraction (XRD) analysis. Under a 980-nm continuous wave laser diode (LD) excitation, the phosphors exhibited UV UC fluorescence of Gd3+ peaking at 246.4, 252.8, 276.2, 279.2, 305.8, and 311.4nm, respectively. At the same

Chunyan Cao; Xianmin Zhang; Minglun Chen; Weiping Qin; Jisen Zhang

2010-01-01

116

Additive colouring of CaF2:Yb crystals: determination of Yb2+ concentration in CaF2:Yb crystals and ceramics  

NASA Astrophysics Data System (ADS)

When growing CaF2 crystal doped with rare-earth ions, most of these ions are present in a trivalent state. However, due to contact with graphite crucible, a small proportion of a number of ions (Eu, Sm, Yb and Tm) are reduced to a bivalent state. A similar situation takes place during fabrication of CaF2 ceramics doped with rare-earth metals. This fact is of particular importance for laser CaF2:Yb crystals (ceramics), a promising material for short-pulse, high-power, high-energy diode-pumped solid state lasers since the presence of bivalent Yb ions can be a source of thermal losses. To date, there has been no technique to determine Yb2+ concentration in as-grown crystals. The proposed technique is based on a total reduction of Yb3+ ions via the heating of as-grown CaF2 crystals with known concentration of Yb in the reducing atmosphere of metal vapour and determining the cross section of absorption bands of Yb2+ ions. The knowledge of these parameters allows estimation of the Yb2+ content in CaF2:Yb crystals or ceramics by analysing their absorption spectra. Examples of using this technique are given. The technology of CdF2 crystals reduction (an "additive colouring") and features of colouring of crystals doped with rare-earth ions are considered.

Shcheulin, A. S.; Angervaks, A. E.; Semenova, T. S.; Koryakina, L. F.; Petrova, M. A.; Fedorov, P. P.; Reiterov, V. M.; Garibin, E. A.; Ryskin, A. I.

2013-06-01

117

High pressure effect on structural and mechanical properties of some LnO (Ln=Sm, Eu, Yb) compounds  

NASA Astrophysics Data System (ADS)

The structural and mechanical properties of LnO (Ln=Sm, Eu, Yb) compounds have been investigated using a modified interionic potential theory, which includes the effect of Coulomb screening. We predicted a structural phase transition from NaCl (B 1)- to CsCl (B 2)-type structure and elastic properties in LnO compounds at very high pressure. The anomalous properties of these compounds have been correlated in terms of the hybridisation of f-electrons of the rare earth ion with conduction band and strong mixing of f-states of lanthanides with the p-orbital of neighbouring chalcogen ion. For EuO, the calculated transition pressure, bulk modulus and lattice parameter are close to the experimental data. The nature of bonds between the ions is predicted by simulating the ion-ion (Ln-Ln and Ln-O) distances at high pressure. The second order elastic constants along with shear modulus and Young's modulus, elastic anisotropy and Poisson's ratio are also presented for these oxides.

Srivastava, Vipul; Bhajanker, Sanjay; Sanyal, Sankar P.

2011-05-01

118

Synthesis, crystal structures, magnetic and electric transport properties of Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}  

SciTech Connect

Two new rare-earth metal containing Zintl phases, Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9} have been synthesized by reactions of the corresponding elements in molten In metal to serve as a self-flux. Their crystal structures have been determined by single crystal X-ray diffraction-both compounds are isostructural and crystallize in the orthorhombic space group Iba2 (No. 45), Z=4 with unit cell parameters a=12.224(2) A, b=12.874(2) A, c=17.315(3) A for Eu{sub 11}InSb{sub 9}, and a=11.7886(11) A, b=12.4151(12) A, c=16.6743(15) A for Yb{sub 11}InSb{sub 9}, respectively (Ca{sub 11}InSb{sub 9}-type, Pearson's code oI84). Both structures can be rationalized using the classic Zintl rules, and are best described in terms of discrete In-centered tetrahedra of Sb, [InSb{sub 4}]{sup 9-}, isolated Sb dimers, [Sb{sub 2}]{sup 4-}, and isolated Sb anions, Sb{sup 3-}. These anionic species are separated by Eu{sup 2+} and Yb{sup 2+} cations, which occupy the empty space between them and counterbalance the formal charges. Temperature-dependent magnetic susceptibility and resistivity measurements corroborate such analysis and indicate divalent Eu and Yb, as well as poorly metallic behavior for both Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}. The close relationships between these structures and those of the monoclinic {alpha}-Ca{sub 21}Mn{sub 4}Sb{sub 18} and Ca{sub 21}Mn{sub 4}Bi{sub 18} are also discussed. - Graphical abstract: Reported are the synthesis, the structure and the magnetic and electronic properties of two new rare-earth Zintl phases, Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}. The close relationships between these structures and those of the monoclinic {alpha}-Ca{sub 21}Mn{sub 4}Sb{sub 18} and Ca{sub 21}Mn{sub 4}Bi{sub 18} are also discussed.

Xia Shengqing [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Hullmann, Jonathan [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)], E-mail: bobev@udel.edu; Ozbay, Arif [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Nowak, Edmund R. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Fritsch, Veronika [Physikalisches Institut, Universitaet Karlsruhe (Thailand), 76128 Karlsruhe (Germany)

2007-07-15

119

The application of {(DMF) 10Yb 2[TM(CN) 4] 3} ? (TM = Ni, Pd) supported on silica to promote gas phase phenol hydrogenation  

Microsoft Academic Search

The catalytic gas phase phenol hydrogenation activities\\/selectivities associated with Pd\\/SiO2 prepared by Pd(NO3)2 and Pd(C2H3O2)2 impregnation have been compared with those delivered by Pd–Yb\\/SiO2 prepared from a {(DMF)10Yb2[Pd(CN)4]3}? precursor. The Pd metal loading spanned the range 1–10% (w\\/w) and the reaction was conducted over the temperature interval 398–448K. Phenol hydrogenation yielded both cyclohexanone as a partially hydrogenated reactive intermediate and

Sheldon G Shore; Errun Ding; Colin Park; Mark A Keane

2004-01-01

120

Anti-cAngptl4 Ab-conjugated N-TiO(2) /NaYF(4) :Yb,Tm nanocomposite for near infrared-triggered drug release and enhanced targeted cancer cell ablation.  

PubMed

Nanomedicine: NIR-active N-TiO(2) /NaYF(4) :Yb,Tm nanocomposites (NCs) were synthesized for the first time and its potential applications in drug release and targeted cancer cell ablation are explored. Upon 980 nm laser irradiation, the anti-cAngptl4 Ab-conjugated N-TiO(2) /NaYF(4) :Yb,Tm NCs shows a significant increase in apoptotic A-5RT3 cells when compared with that of the unconjugated NCs. The mechanisms for NIR-induced photocatalysis, drug release and targeted cancer cell killing are proposed. PMID:23184779

Xu, Qing Chi; Zhang, Yan; Tan, Ming Jie; Liu, Yang; Yuan, Shaojun; Choong, Cleo; Tan, Nguan Soon; Tan, Timothy Thatt Yang

2012-07-01

121

Energy Levels of 68Er166 and 69Tm166 (7.7 h) Excited in the Decay of 67Ho166 (26.7 h), Ho166m (1.2×103 yr), and 70Yb166 (57 h)  

Microsoft Academic Search

The gamma-ray spectra accompanying the decay of 67Ho166 (26.7 h), 67Ho166m (1.2×103 yr), 70Yb166 (57 h), and 69Tm166 (7.7 h) have been examined with Ge(Li) detectors. Chemically purified sources of Yb166 revealed only the known 82.3-keV transition in Tm166. Nine transitions observed in the 26.7-h Ho166 activity fit known excited levels in Er166: 80.57 (2+), 786.4 (2+), the 1460.9-keV (0+)

S. B. Burson; P. F. Goudsmit; J. Konijn

1967-01-01

122

Separation of the contributions to the magnetization of Tm1 - x Yb x B12 solid solutions in steady and pulsed magnetic fields  

NASA Astrophysics Data System (ADS)

The magnetization of substitutional Tm1 - x Yb x B12 solid solutions is studied in the composition range 0 < x ? 0.81. The measurements are performed at low temperatures (1.9-300 K) in steady (up to 11 T) and pulsed (up to 50 T, pulse duration of 20-100 ms) magnetic fields. An analysis of the experimental data allowed the contributions to the magnetization of the paramagnetic phase of the Tm1 - x Yb x B12 compounds to be separated. These contributions include a Pauli component, which corresponds to the response of the heavy-fermion manybody states that appears in the energy gap in the vicinity of the Fermi level (density of states (3-4) × 1021 cm-3 meV-1), and a contribution with saturation in high magnetic fields attributed to the localized magnetic moments ((0.8-3.7)?B per unit cell) of the nanoclusters formed by rare-earth ions with an antiferromagnetic interaction.

Bogach, A. V.; Sluchanko, N. E.; Glushkov, V. V.; Demishev, S. V.; Azarevich, A. N.; Filippov, V. B.; Shitsevalova, N. Yu.; Levchenko, A. V.; Vanacken, J.; Moshchalkov, V. V.; Gabani, S.; Flachbart, K.

2013-05-01

123

Eu3+ and Yb3+ codoped Gd2O3 single phase nanophosphor: An enhanced monochromatic red emission through cooperative upconversion and downconversion  

Microsoft Academic Search

Single phase cubic Gd2O3 nanophosphor codoped with Eu3+ and Yb3+ ions has been synthesized through solution combustion route. Structural properties have been investigated using x-ray diffraction (XRD) and transmission electron microscopy (TEM). The as-synthesized Gd2O3 phosphor shows amorphous nature which changes to crystalline single cubic phase on annealing. Optical properties have been investigated through absorption, photoluminescence, and lifetime measurements. Intense

Gagandeep Kaur; S. K. Singh; S. B. Rai

2010-01-01

124

Influence of Various Impurities on the Optical Properties of YbF3-Doped CaF2 Crystals  

Microsoft Academic Search

Calcium fluoride crystals doped with YbF3 and co-doped with LiF and NaF were grown using the vertical Bridgman method. Several of rare-earth ions (such as Eu, Sm, Ho, Tm, and Yb) can be stabilized in the divalent state in the CaF2. The change of valence was attained by various methods. The optical absorption spectra reveal the characteristic absorption bands of

M. Stef; A. Pruna; N. Pecingina-Garjoaba; I. Nicoara

2007-01-01

125

[High current microsecond pulsed hollow cathode lamp excited inductively coupled plasma ionic fluorescence spectrometry of Eu, Yb, Ca, Sr and Ba with an extended-sleeve torch].  

PubMed

Inductively coupled plasma (ICP) is a powerful atomizer for atomic fluorescence spectrometry (AFS), but high degree of ionization in high temperature of plasma at lower observation height and easy combination with oxygen at high observation height significantly decrease fluorescence intensity of refractory elements. Inoic fluorescence spectrometry (IFS) of Eu, Yb, Ca, Sr and Ba was investigated with high current microsecond pulsed (HCMP) hollow cathode lamps (HCLs) and an extended-sleeve torch adopted in commercial Baird Plasma AFS 2000 fluorescence spectrometer. Without introduction of any organic gas or solvent into the plasma, the detection limits (DLs) with HCMP-HCL-IFS was improved by about 1.5 order of magnitude (37x) for Sr, by over 2 orders of magnitude for Ba, and by nearly 1 order of magnitude for Eu and Yb as compared to those of conventionally pulsed (ICP-HCL-AFS). The HCMP IFS DLs of Eu and Yb were even superior to those of dye laser excited IFS reported in literatures. PMID:12945316

Zhang, S Y; Huang, B L; Gong, Z B

2001-10-01

126

Synergistic extraction of Ce(III), Eu(III) and Tm(III) with a mixture of picrolonic acid and benzo-15-crown-5 in chloroform  

Microsoft Academic Search

Summary  The synergistic mixture comprising picrolonic acid (HPA) and benzo-15-crown-5 (B15C5) in chloroform has been used for the\\u000a extraction of Ce(III), Eu(III) and Tm(III) as representatives of lanthanide(III) ions from pH 1-2 solutions having ionic strength\\u000a of 0.1 mol. dm-3(K+\\/H+, Cl-). The composition of the extracted species has been determined as M(PA)3. nB15C5 where M is Ce, Eu and Tm and

Akbar Ali; Jamil Anwar; Wasim Yawar

2006-01-01

127

Photoluminescence properties of Tm3+/Tb3+/Eu3+ tri-doped phosphate glass and glass ceramics for white-light-emitting diodes.  

PubMed

Tm(3+)/Tb(3+)/Eu(3+) tri-doped phosphate glasses are synthesized to explore new white-light-emitting materials. Under 365 nm excitation, the CIE coordinates (x=0.339, y=0.341) of the Eu0.07 glass sample are close to the standard equal energy white-light illumination (x=0.333, y=0.333). The quantum efficiency is very high (~72.27%). The energy transition from Tb(3+) to Eu(3+) is reasonably interpreted based on the analysis of the luminescence lifetimes. To enhance the white-light emission, Tm(3+)/Tb(3+)/Eu(3+) tri-doped phosphate glass ceramics are prepared. PMID:23938408

Yu, Yin; Song, Feng; Ming, Chengguo; Zhang, Jun; Wang, Fengxiao

2013-08-10

128

CRYSTAL STRUCTURE AND OPTICAL PROPERTIES OF SYSTEMS LnF3-CeF3 (Ln-Sm, Eu, Yb) AND EuF3-TbF3  

Microsoft Academic Search

The interaction and structure of phases in systems LnF3-Ln'F3 (Ln-Sm, Eu, Yb Ln'-Ce, Tb) are studied at 700 -1100°C. Formation of solid solutions on the basis of binary fluorides of lanthanides is established. Appearance of fluorite-like phases of a structure LnF2+x beginning from 1000°C is observed. The content of the latter notably increases at heat treatment in vacuum. The formation

V. Zinchenko; O. Eryomin; N. Efryushina; I. Stoyanova; V. Markiv; N. Belyavina

129

An efficient and user-friendly method for the synthesis of hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with controllable shape and upconversion fluorescence  

NASA Astrophysics Data System (ADS)

Hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals are the best IR-to-visible upconverting materials to date, but user-friendly methods for making pure hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with upconversion fluorescence are still lacking. Most of the methods reported so far require excess fluoride reactants in a high-temperature reaction which are very unfriendly to users and raise safety concerns. In this work, an efficient and user-friendly method was developed for the synthesis of uniform hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with upconversion fluorescence, by forming small solid-state crystal nuclei and further growth and ripening of the nuclei. NaYF4:Yb, Er/Tm nanoplates, nanospheres and nanoellipses were also selectively produced by varying the concentration of the surfactant. All the nanocrystals showed strong upconversion fluorescence, and fluorescence from the nanoplates was observed even when the laser power density was reduced to about 50 mW cm-2. These nanocrystals have great potential for use in biology and medicine as fluorescent labels or imaging probes.

Li, Zhengquan; Zhang, Yong

2008-08-01

130

An efficient and user-friendly method for the synthesis of hexagonal-phase NaYF(4):Yb, Er/Tm nanocrystals with controllable shape and upconversion fluorescence.  

PubMed

Hexagonal-phase NaYF(4):Yb, Er/Tm nanocrystals are the best IR-to-visible upconverting materials to date, but user-friendly methods for making pure hexagonal-phase NaYF(4):Yb, Er/Tm nanocrystals with upconversion fluorescence are still lacking. Most of the methods reported so far require excess fluoride reactants in a high-temperature reaction which are very unfriendly to users and raise safety concerns. In this work, an efficient and user-friendly method was developed for the synthesis of uniform hexagonal-phase NaYF(4):Yb, Er/Tm nanocrystals with upconversion fluorescence, by forming small solid-state crystal nuclei and further growth and ripening of the nuclei. NaYF(4):Yb, Er/Tm nanoplates, nanospheres and nanoellipses were also selectively produced by varying the concentration of the surfactant. All the nanocrystals showed strong upconversion fluorescence, and fluorescence from the nanoplates was observed even when the laser power density was reduced to about 50 mW cm(-2). These nanocrystals have great potential for use in biology and medicine as fluorescent labels or imaging probes. PMID:21730655

Li, Zhengquan; Zhang, Yong

2008-08-27

131

Excitation mechanism of the upper \\/sup 1\\/D\\/sub 2\\/ and \\/sup 3\\/P\\/sub 0\\/ levels in Tm:Yb:BaY\\/sub 2\\/F\\/sub 8\\/ laser crystal  

Microsoft Academic Search

Summary form only given. We quantitatively studied upconversion in Tm,Yb:BaY\\/sub 2\\/F\\/sub 5\\/ laser crystal, determined the excitation scheme for the upper \\/sup 1\\/D\\/sub 2\\/ and \\/sup 5\\/P\\/sub 0\\/ metastable levels, and showed the possibility of avalanche pumping at 706 nm.

M. A. Noginov; M. Curley; P. Venkateswarlu; H. P. Jenssen

1996-01-01

132

A systematic study of the oxygen K edge in the cubic and less common monoclinic phases of the rare earth oxides (Ho, Er, Tm, Yb) by electron energy loss spectroscopy  

Microsoft Academic Search

Transmission electron microscopy and electron energy loss spectroscopy (EELS) were used to distinguish structural details for the cubic and uncommon monoclinic crystal phases of heavy metal rare earth oxide nanoparticles synthesized by a combustion process. Specifically, we systematically examined the EELS oxygen K edge for Ho, Tm, Er, and Yb sesquioxides in both phases. This work presents, to our knowledge,

Ashley Harvey; Bing Guo; Ian Kennedy; Subhash Risbud; Valerie Leppert

2006-01-01

133

Magnetic susceptibility of sodium rare-earth fluorites Na 0.5 ? x R 0.5 + x F 2 + 2 x ( R = Dy, Ho, Er, Tm, Yb) and some ordered phases  

Microsoft Academic Search

Magnetic properties of the nonstoichiometric phases with the fluorite-type “defect” structure Na0.4\\u000a R\\u000a 0.6F2.2 (R = Ho, Er, Tm, Yb) and Na0.35Dy0.65F2.3 have been studied as well as some ordered phases with different distortions of the initial fluorite lattice (NaHo2F7, Na7Tm13F46, NaYb2F7, and Na7Yb13F46) and Na1.5Dy1.5F6 with the gagarinite-type structure (NaCaYF6). Magnetic susceptibility ? was measured with the aid of

X. Bohigas; J. Lluma; J. Tejada; E. A. Krivandina; B. P. Sobolev

2001-01-01

134

Superconductivity of metal nitride chloride ?-MNCl (M = Zr, Hf) with rare-earth metal RE (RE = Eu, Yb) doped by intercalation  

NASA Astrophysics Data System (ADS)

Electrons were doped into the ?-form layered metal nitride chloride MNCl (M = Zr, Hf) by intercalation of rare-earth metals RE (RE = Eu, Yb) using liquid ammonia solutions. The intercalated compounds REx(NH3)yMNCl show superconductivity with transition temperatures Tc of ˜13 and 24.3 K for M = Zr and Hf, respectively, quite similar to the alkali metal intercalated analogs. The paramagnetic characteristics for Eu2+ and Yb3+ can coexist with superconductivity. The magnetic resistance measured on the uniaxially oriented Eu0.08(NH3)yHfNCl with the magnetic field parallel to the ab plane (? ab) and the c axis (? c) shows a strong anisotropic effect on the upper critical field Hc2; a large anisotropic parameter \\gamma ={H}_{{c}2}^{\\parallel a b}/{H}_{{c}2}^{\\parallel c}\\sim 4 suggests a pseudo-two-dimensional superconductivity. The Tc of Eu0.13(THF)yHfNCl is shifted toward a higher value of 25.8 K upon expansion of the interlayer spacing from 11.9 to 17.5 Å by co-intercalation of voluminous organic molecules such as tetrahydrofuran.

Zhang, Shuai; Tanaka, Masashi; Onimaru, Takahiro; Takabatake, Toshiro; Isikawa, Yosikazu; Yamanaka, Shoji

2013-04-01

135

Controlled growth, intense upconversion emissions and concentration induced luminescence switching of bifunctional Tm(3+) doped hexagonal NaYb0.55Gd0.45F4 nanorods.  

PubMed

Bifunctional hexagonal Tm(3+) doped NaYb0.55Gd0.45F4 nanorods with tunable size are prepared via in situ cation-exchange reaction using hydrothermal method. The measured field dependence of magnetization of the NaYb0.55Gd0.45F4 nanorods shows typical paramagnetic characteristics that can be ascribed to the non-interacting localized nature of the magnetic moment of rare-earth ions. When excited by a 980nm laser, these nanorods exhibit intense multi-color up-conversion (UC) emissions in infrared, red, blue and especially ultraviolet. In addition, luminescent switching between different UC emission wavelengths of 480nm and 450nm is observed by adjusting Tm(3+) doping concentration. Based on power-dependent spectral analyses, it is found that with the increase of Tm(3+) doping concentration, due to the suppressed saturation effect, the dominative UC process redistribute the populations at (1)G4 and (1)D2(Tm(3+)) states of Tm(3+) ion resulting in the above luminescent switching. Our results indicate that bifunctional hexagonal NaYb1-xGdxF4 nanocrystals have potential applications in miniaturized solid-state light sources, optical processing sensors and fluorescent biolabels. PMID:23871979

Qu, Xilong; Li, Yongchang; Yu, Suixi; Yang, Liwen

2013-11-01

136

Double pulse laser deposition of polymer nanocomposite: NaYF4:Tm3+,Yb3+ films for optical sensors and light emitting applications  

NASA Astrophysics Data System (ADS)

The main objective of this paper is to demonstrate the feasibility of producing operationally Nanocomposite polymeric thin films for sensor and light emitting applications using the innovative modified double pulsed laser deposition (DPLD) technique. The existing PLD vacuum chamber was modified to accommodate multiple wavelength laser beams for in-situ-double-ablation/Deposition (DPLD) of multiple targets of host and dopants. Special design was made for cooling of the target to the threshold of the polymer ablation without interrupting the continuity of the ablation process. Multilayered of nanocomposites of acrylic polymers and nanoparticles of NaYF4:Tm3+ ,Yb3+ are fabricated using ultra-violet (UV) radiation (355 nm) ablating polymer targets and near-infra-red (near-IR) radiation (1064 nm) ablating inorganic targets. The films were characterized using the reflected high energy electron diffraction (RHEED), XRD , XRF, AFM, and FTIR absorption spectroscopy and tested as possible chemical sensors and light emitters.

Darwish, Abdalla M.; Wilson, Simeon; Sarkisov, Sergey; Patel, Darayas

2013-09-01

137

Rapid microwave-enhanced hydrothermal synthesis and shape evolution of uniform NaGdF4:Yb, Er (Tm/Ho) nanocrystals with upconversion and paramagnetic properties  

NASA Astrophysics Data System (ADS)

An efficient microwave-enhanced hydrothermal synthesis strategy was developed for the rapid synthesis of ?-NaGdF4:Ln3+ (Ln = Yb, Er/Tm/Ho) nanocrystals (NCs) with multicolour upconversion luminescence and paramagnetic properties. It has been found that the uniform ?-NaGdF4:Ln3+ NCs could be rapidly formed within a few minutes at 160?°C and the shape of the NCs can be manipulated from uniform rod-like to spherical just by tuning the initial reactants’ concentration. In comparison to conventional hydrothermal routes, a burst homogeneous nucleation and higher growth rate as well as enhanced dimensional homogeneity of the NaGdF4:Ln3+ was achieved in microwave synthesis. A microwave-heating-based classical crystallization mode and surfactant-assisted anisotropic growth mechanism were proposed for the formation of ?-NaGdF4:Ln3+ NCs.

Wang, Dong; Ren, Lei; Zhou, Xi; Wang, Xiao-zhong; Zhou, Jun; Han, Yu; Kang, Ning

2012-06-01

138

Rational morphology control of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors using a ligand, an additive, and lanthanide doping  

NASA Astrophysics Data System (ADS)

We report the systematic control of the morphology of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors (UCNPs) from large spheres (37.9 nm) to rods (length = 60.1 nm, width = 21.5 nm) and from rods to hexagonal prisms (length = 48.8 nm, width = 44.0 nm) or small spheres (14.0 nm) by the use of a surfactant, an additive, and lanthanide doping. Increasing the ratio of oleic acid (OA) to 1-octadecene (ODE) caused a decrease in the size of the UCNPs, and increasing the OA/ODE ratio above a critical value caused the particle shape to change from a sphere to a rod. The length-to-width aspect ratio (AR) of upconversion nanorods (UCNRs) was finely manipulated from 1.28 to 2.80. The rounded tips of the UCNRs were flattened by adding Cl- ions, and the UCNRs changed to hexagonal prisms with a controllable AR depending on the quantity of Cl- ions. Additionally, the morphology of the ?-NaYF4-based UCNPs was controlled by lanthanide doping. The size and AR of the UCNRs decreased with Gd3+ doping, and the UCNRs ultimately transformed into small spheres (14.0 nm) with high monodispersity. Doping with Ce3+ ions also decreased the AR of the UCNRs from 2.80 to 1.27. In addition, highly transparent polymer composites for 3D volumetric displays were fabricated by blending high-AR ?-NaYF4:Yb,Er/Tm UCNRs with polydimethylsiloxane. These composites exhibited bright green and blue upconversion light during excitation with 980 nm light.We report the systematic control of the morphology of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors (UCNPs) from large spheres (37.9 nm) to rods (length = 60.1 nm, width = 21.5 nm) and from rods to hexagonal prisms (length = 48.8 nm, width = 44.0 nm) or small spheres (14.0 nm) by the use of a surfactant, an additive, and lanthanide doping. Increasing the ratio of oleic acid (OA) to 1-octadecene (ODE) caused a decrease in the size of the UCNPs, and increasing the OA/ODE ratio above a critical value caused the particle shape to change from a sphere to a rod. The length-to-width aspect ratio (AR) of upconversion nanorods (UCNRs) was finely manipulated from 1.28 to 2.80. The rounded tips of the UCNRs were flattened by adding Cl- ions, and the UCNRs changed to hexagonal prisms with a controllable AR depending on the quantity of Cl- ions. Additionally, the morphology of the ?-NaYF4-based UCNPs was controlled by lanthanide doping. The size and AR of the UCNRs decreased with Gd3+ doping, and the UCNRs ultimately transformed into small spheres (14.0 nm) with high monodispersity. Doping with Ce3+ ions also decreased the AR of the UCNRs from 2.80 to 1.27. In addition, highly transparent polymer composites for 3D volumetric displays were fabricated by blending high-AR ?-NaYF4:Yb,Er/Tm UCNRs with polydimethylsiloxane. These composites exhibited bright green and blue upconversion light during excitation with 980 nm light. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00080j

Na, Hyejin; Woo, Kyoungja; Lim, Kipil; Jang, Ho Seong

2013-05-01

139

Development and performance characteristics of flash lamp pumped Yb:YAG, Cr:Tm:Ho:YAG, Er:Tm:Ho:YLF laser sources and investigation of their potential biological applications  

NASA Astrophysics Data System (ADS)

Laser ablation for the formation of apodized patterns on intraocular lenses, as an alternative of the conventional injection molding, has been proved to be a very promising new technique. For the precise lenses ablation, the use of suitable laser wavelength and pulse duration, resulting in a small optical penetration depth in the lens and in confinement of the energy deposition in a small volume, as well as the reduced thermal damage to the surrounding tissue, is essential. Mid-infrared laser wavelengths, at which the organic biological simulators absorption coefficient is large, meet well the above conditions. Towards the complete understanding of the intraocular lens ablation procedure and therefore the choice of the optimum laser beam characteristics for the most accurate, efficient and safe surgical application, the comparative study of various mid-infrared laser sources is of great interest. In this work we investigate the potential of the development of three different mid-infrared laser sources, namely the Yb:YAG, the Cr:Tm:Ho:YAG and the Er:Tm:Ho:YLF laser, operating at 1029 nm, 2060 nm and 2080 nm respectively and their ability in forming patterns on biomaterials. Pumping was achieved with conventional Xe flash lamps in a double elliptical pump chamber. A properly designed Pulse-Forming- Network capable of delivering energy up to 800 J, in variable lamp illumination durations is used. Several hundreds of mJoules were achieved from the Yb:YAG laser oscillator and several Joules from the Ho:YAG and Ho:YLF laser oscillators. Free running and Q-switched laser operation studies and preliminary experiments on laser and biomaterials (biopolymers and animal tissues) interactions will be reported.

Karadimitriou, N.; Klinkenberg, B.; Papadopoulos, D. N.; Serafetinides, A. A.

2007-06-01

140

Rational morphology control of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors using a ligand, an additive, and lanthanide doping.  

PubMed

We report the systematic control of the morphology of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors (UCNPs) from large spheres (37.9 nm) to rods (length = 60.1 nm, width = 21.5 nm) and from rods to hexagonal prisms (length = 48.8 nm, width = 44.0 nm) or small spheres (14.0 nm) by the use of a surfactant, an additive, and lanthanide doping. Increasing the ratio of oleic acid (OA) to 1-octadecene (ODE) caused a decrease in the size of the UCNPs, and increasing the OA/ODE ratio above a critical value caused the particle shape to change from a sphere to a rod. The length-to-width aspect ratio (AR) of upconversion nanorods (UCNRs) was finely manipulated from 1.28 to 2.80. The rounded tips of the UCNRs were flattened by adding Cl(-) ions, and the UCNRs changed to hexagonal prisms with a controllable AR depending on the quantity of Cl(-) ions. Additionally, the morphology of the ?-NaYF4-based UCNPs was controlled by lanthanide doping. The size and AR of the UCNRs decreased with Gd(3+) doping, and the UCNRs ultimately transformed into small spheres (14.0 nm) with high monodispersity. Doping with Ce(3+) ions also decreased the AR of the UCNRs from 2.80 to 1.27. In addition, highly transparent polymer composites for 3D volumetric displays were fabricated by blending high-AR ?-NaYF4:Yb,Er/Tm UCNRs with polydimethylsiloxane. These composites exhibited bright green and blue upconversion light during excitation with 980 nm light. PMID:23546176

Na, Hyejin; Woo, Kyoungja; Lim, Kipil; Jang, Ho Seong

2013-05-21

141

Eu3+ and Yb3+ codoped Gd2O3 single phase nanophosphor: An enhanced monochromatic red emission through cooperative upconversion and downconversion  

NASA Astrophysics Data System (ADS)

Single phase cubic Gd2O3 nanophosphor codoped with Eu3+ and Yb3+ ions has been synthesized through solution combustion route. Structural properties have been investigated using x-ray diffraction (XRD) and transmission electron microscopy (TEM). The as-synthesized Gd2O3 phosphor shows amorphous nature which changes to crystalline single cubic phase on annealing. Optical properties have been investigated through absorption, photoluminescence, and lifetime measurements. Intense red emission (5D0-->7F2) is observed both from cooperative upconversion (Yb3++Yb3+-->Eu3+ on 976 nm excitation) as well as through downconversion process (on 355 nm excitation). The unusual and rarely reported emissions from the higher lying 5DJ (J=2, 3, and 4) to 7FJ (J=0, 1, 2, 3, and 4) levels are also observed with 976 nm excitation. Nearly twenty two times enhancement in the intensity of the hypersensitive transition (5D0-->7F2) along with an increase in the decay time (770 ?s) is observed for the sample annealed at 1200 °C on 355 nm excitation. These observations have been explained satisfactorily.

Kaur, Gagandeep; Singh, S. K.; Rai, S. B.

2010-04-01

142

Photoluminescence properties of rare earths (Eu 3+, Tb 3+, Dy 3+ and Tm 3+) activated NaInW 2O 8 wolframite host lattice  

NASA Astrophysics Data System (ADS)

The photoluminescence (PL) studies on NaIn 1- xRExW 2O 8, with RE=Eu 3+, Tb 3+, Dy 3+ and Tm 3+ phases have shown that the relative contribution of the host lattice and of the intra- f-f emission of the activators to the PL varies with the nature of the rare earth cation. In the case of Dy 3+ and Tm 3+ activators, with yellow and blue emission, respectively, the energy transfer from host to the activator plays a major role. In contrast for Eu 3+, with intense red emission, the host absorption is less pronounced and the intra- f-f transitions of the Eu 3+ ions play a major role, whereas for Tb 3+ intra- f-f transitions are only observed, giving rise to green emission.

Asiri Naidu, S.; Boudin, S.; Varadaraju, U. V.; Raveau, B.

2012-01-01

143

Triple-layered perovskite niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y): new self-activated oxides.  

PubMed

Niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y) were prepared by conventional high-temperature solid-state reaction. The formation of a single-phase compound with triple-layered perovskite-type structure was verified through X-ray diffraction (XRD) studies. The luminescence characteristics such as photoluminescence excitation and emission spectra, X-ray-excited luminescence (XEL), Stokes shift, decay curves, and color coordinates were investigated. The niobates can be efficiently excited by UV light and present luminescence behaviors with rich luminescence colors. Under excitation by ultraviolet radiation, CaRNb3O10 (R = La, Gd, Yb, or Y) exhibits strong blue luminescence due to the self-activation center of the octahedral NbO6 groups, even at room temperature. For the materials of composition CaRNb3O10 (R = Sm, Eu, Dy, or Er), the excitation at the host band produces a characteristic luminescence of rare earth ions, indicating a host-guest energy transfer process. CaRNb3O10 (R = Eu) has the strongest luminescence intensity, which can be efficiently excitated by near UV wavelength. It could be suggested to be a potential candidate for the application on near-UV excited white LEDs. PMID:23977903

Qin, Lin; Wei, Donglei; Huang, Yanlin; Kim, Sun Il; Yu, Young Moon; Seo, Hyo Jin

2013-09-16

144

Structural and Magnetothermal Properties of Compounds: Yb5SixGe4-x,Sm5SixGe4-x, EuO, and Eu3O4  

SciTech Connect

The family of R{sub 5}Si{sub x}Ge{sub 4-x} alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R{sub 5}Si{sub x}Ge{sub 4-x} systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R{sub 5}Si{sub x}Ge{sub 4-x} systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb{sub 5}Si{sub x}Ge{sub 4-x} and Sm{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys with 0 {le} x {le} 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R{sub 5}Si{sub x}Ge{sub 4-x} systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd{sub 5}Si{sub 4}-type structure. The magnetic properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} materials are nearly composition-independent, reflecting the persistence of the same crystal structure over the whole range of x from 0 to 4. Both the crystallographic and magnetic property data indicate that Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys are mixed valence systems, in which the majority (60%) of Yb atoms is divalent, while the minority (40%) is trivalent. This finding is supported by recent Moessbauer spectroscopy data.

Kyunghan Ahn

2007-05-09

145

Controllable red, green, blue (RGB) and bright white upconversion luminescence of Lu2O3:Yb3+/Er3+/Tm3+ nanocrystals through single laser excitation at 980 nm.  

PubMed

Light fantastic! Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals with controllable red, green, blue (RGB) and bright white upconversion luminescence by a single laser excitation of 980 nm have been successfully synthesized (see picture). Due to abundant UC PL colors, it can potentially be used as fluorophores in the field of color displays, back light, UC lasers, photonics, and biomedicine.Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals have been successfully synthesized by a solvothermal process followed by a subsequent heat treatment at 800 degrees C. Powder X-ray diffraction, transmission electron microscopy, upconversion photoluminescence spectra, and kinetic decay were used to characterize the samples. Under single-wavelength diode laser excitation of 980 nm, the bright blue emissions of Lu(2)O(3):Yb(3+), Tm(3+) nanocrystals near 477 and 490 nm were observed due to the (1)G(4)-->(3)H(6) transition of Tm(3+). The bright green UC emissions of Lu(2)O(3):Er(3+) nanocrystals appeared near 540 and 565 nm were observed and assigned to the (2)H(11/2)-->(4)I(15/2) and (4)S(3/2)-->(4)I(15/2) transitions, respectively, of Er(3+). The ratio of the intensity of green luminescence to that of red luminescence decreases with an increase of concentration of Yb(3+) in Lu(2)O(3):Er(3+) nanocrystals. In sufficient quantities of Yb(3+) with resprct to Er(3+), the bright red UC emission of Lu(2)O(3):Yb(3+)/Er(3+) centered at 662 nm was predominant, due to the (4)F(9/2)-->(4)I(15/2) transition of Er(3+). Based on the generation of red, green, and blue emissions in the different doped Lu(2)O(3):RE(3+) nanocrystals, it is possible to produce the luminescence with a wide spectrum of colors, including white, by the appropriate doping of Yb(3+), Tm(3+), and Er(3+) in the present Lu(2)O(3) nanocrystals. Namely, Lu(2)O(3):3 %Yb(3+)/0.2 %Tm(3+)/0.4 %Er(3+) nanocrystals show suitable intensities of blue, green, and red (RGB) emission, resulting in the production of perfect and bright white light with CIE-x=0.3456 and CIE-y=0.3179, which is very close to the standard equal energy white light illuminate (x=0.33, y=0.33). Because of abundant luminescent colors from RGB to white in Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals under 980 nm laser diode (LD) excitation, they can potentially be used as fluorophores in the field of color displays, back light, UC lasers, photonics, and biomedicine. PMID:19296483

Yang, Jun; Zhang, Cuimiao; Peng, Chong; Li, Chunxia; Wang, Lili; Chai, Ruitao; Lin, Jun

2009-01-01

146

Interplay between Cu and Fe Valences in Ba R(Cu 0.5Fe 0.5) 2O 5+ ? Double Perovskites with R=Lu, Yb, Y, Eu, Sm, Nd, and Pr  

Microsoft Academic Search

We have conducted a systematic 57Fe Mössbauer study on BaR(Cu0.5Fe0.5)2O5+? double perovskites with various oxygen contents and rare-earth elements (R=Lu, Yb, Y, Eu, Sm, Nd, and Pr). In samples based on R=Lu, Yb, Y, Eu, Sm the oxygen content remained at ??0, upon reductive or oxidative heat treatments under normal pressure. The larger rare-earth elements, i.e. Nd or Pr, readily

J. Lindén; M. Kochi; K. Lehmus; T. Pietari; M. Karppinen; H. Yamauchi

2002-01-01

147

Upconversion Nanophosphors Naluf4:Yb,Tm for Lymphatic Imaging In Vivo by Real-Time Upconversion Luminescence Imaging under Ambient Light and High-Resolution X-ray CT  

PubMed Central

Lanthanide upconversion nanophosphor (UCNP) has attracted increasing attention for potential applications in bioimaging due to its excellence in deep and high contrast imaging. To date, most upconversion imaging applications were demonstrated in dark surroundings without ambient light for higher signal-to-noise ratio, which hindered the application of optical imaging guided surgery. Herein, the new established NaLuF4-based UCNP (NaLuF4:Yb,Tm, ~17 nm) with bright upconversion emission around 800 nm as imaging signal was used to realize imaging under ambient light to provide more convenient for clinician. Moreover, due to the existance of heavy element lutetium (Lu) in the host lattice, the NaLuF4:Yb,Tm nanoparticles can also be used as an X-ray CT imaging agent to enhance the imaging depth and in vivo imaging resolution.

Sun, Yun; Peng, Juanjuan; Feng, Wei; Li, Fuyou

2013-01-01

148

Upconversion luminescence properties of Yb3+ and Tm3+ codoped amorphous fluoride ZrF4-BaF2-LaF3-AlF3-NaF thin film prepared by pulsed laser deposition.  

PubMed

The Yb3+ and Tm3+ co-doped 55.98ZrF4-28BaF2-2.5LaF3-4AlF3-7NaF-2.5YbF3-0.02TmF3 amorphous fluoride film was prepared by pulsed laser deposition. The spectroscopic properties and energy transfer analysis of this film were studies in detail. Ultraviolet and visible upconversion emissions were observed under the infrared excitation at 980 nm. In comparison with that of its target, the upconversion emissions of the film in the visible and ultraviolet range were greatly enhanced. The possible energy transfer mechanism of the emissions was given to understand the upconversion process. This kind of thin films has potential applications for the integrated optical waveguide amplifier and ultraviolet laser. PMID:24734646

He, Chunfeng; Qin, Guanshi; Zhao, Dan; Chuai, Xiaohong; Wang, Lili; Zheng, Kezhi; Qin, Weiping

2014-05-01

149

Near-infrared photocatalysts of BiVO4/CaF2:Er3+, Tm3+, Yb3+ with enhanced upconversion properties  

NASA Astrophysics Data System (ADS)

Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO).Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO). Electronic supplementary information (ESI) available: Additional tables and figures. See DOI: 10.1039/c3nr05266d

Huang, Shouqiang; Zhu, Nanwen; Lou, Ziyang; Gu, Lin; Miao, Chen; Yuan, Haiping; Shan, Aidang

2014-01-01

150

High-temperature electrical and thermal transport properties of fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb)  

NASA Astrophysics Data System (ADS)

Fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb) have been prepared and the high-temperature electrical and thermal transport properties are investigated systematically. Lattice constants of RFe4Sb12 increase almost linearly with increasing the ionic radii of the fillers, while the lattice expansion in filled structure is weakly influenced by the filler valence charge states. Using simple charge counting, the hole concentration in RFe4Sb12 with divalent fillers (R = Ca, Sr, Ba, Eu, and Yb) is much higher than that in RFe4Sb12 with trivalent fillers (R = La, Ce, Pr, and Nd), resulting in relatively high electrical conductivity and low Seebeck coefficient. It is also found that RFe4Sb12 filled skutterudites having similar filler valence charge states exhibit comparable electrical conductivity and Seebeck coefficient, and the behavior of the temperature dependence, thereby leading to comparable power factor values in the temperature range from 300 to 800 K. All RFe4Sb12 samples possess low lattice thermal conductivity. The correlation between the lattice thermal resistivity WL and ionic radii of the fillers is discussed and a good relationship of WL ~ (rcage-rion)3 is observed in lanthanide metal filled skutterudites. CeFe4Sb12, PrFe4Sb12, and NdFe4Sb12 show the highest thermoelectric figure of merit around 0.87 at 750 K among all the filled skutterudites studied in this work.

Qiu, P. F.; Yang, J.; Liu, R. H.; Shi, X.; Huang, X. Y.; Snyder, G. J.; Zhang, W.; Chen, L. D.

2011-03-01

151

Vibrational structure in optical spectra of the Ca 4GdO(BO 3) 3 (GdCOB) single crystal doped with Re 3+ (Eu, Tb, Yb)  

NASA Astrophysics Data System (ADS)

The optical spectra of compounds containing trivalent rare earth (Re 3+) ions often show vibronic features. The intensity of vibronic transitions is determined by the strength of the electron-phonon (ion-lattice) coupling and depends strongly on the rare earth and the host lattice. In this paper we report on electron-phonon coupling in the GdCOB system doped with Eu 3+, Tb 3+ and Yb 3+ ions. According to general theory intense vibronic lines are to be expected for electronic transitions with ? J=0, ±2 and these transitions were mainly considered in this paper for both Eu 3+ and Tb 3+ ions. In the case of Yb 3+ ions, a strong vibronic sideband belongs to the 2F 7/2? 2F 5/2 transition with ? J=1 although it seems to be in contradiction to the general selection rule. The vibronic features observed in absorption, excitation and emission spectra were analysed on the basis of the host lattice modes obtained from Raman and the far infrared spectra of the matrix.

Dominiak-Dzik, G.; Ryba-Romanowski, W.; Go??b, S.; Baba, M.; Paj?czkowska, A.

2002-09-01

152

Thermoelectric transport properties of CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2  

NASA Astrophysics Data System (ADS)

The thermoelectric transport properties of CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2 were characterized between 2 and 650 K. As synthesized, the polycrystalline samples are found to have lower p-type carrier concentrations than single-crystalline samples of the same empirical formula. These low carrier concentration samples possess the highest mobilities yet reported for materials with the CaAl2Si2 structure type, with a mobility of ˜740 cm2/V/s observed in EuMg2Bi2 at 50 K. Despite decreases in the Seebeck coefficient (?) and electrical resistivity (?) with increasing temperature, the power factor (?2?) increases for all temperatures examined. This behavior suggests a strong asymmetry in the conduction of electrons and holes. The highest figure of merit (zT) is observed in YbMg2Bi2, with zT approaching 0.4 at 600 K for two samples with carrier densities of approximately 2×1018 cm-3 and 8×1018 cm-3 at room temperature. Refinements of neutron powder diffraction data yield similar behavior for the structures of CaMg2Bi2 and YbMg2Bi2, with smooth lattice expansion and relative expansion in c being ˜35% larger than relative expansion in a at 973 K. First-principles calculations reveal an increasing band gap as Bi is replaced by Sb and then As, and subsequent Boltzmann transport calculations predict an increase in ? for a given n associated with an increased effective mass as the gap opens. The magnitude and temperature dependence of ? suggests higher zT is likely to be achieved at larger carrier concentrations, roughly an order of magnitude higher than those in the current polycrystalline samples, which is also expected from the detailed calculations.

May, Andrew F.; McGuire, Michael A.; Singh, David J.; Ma, Jie; Delaire, Olivier; Huq, Ashfia; Cai, Wei; Wang, Hsin

2012-01-01

153

VUV spectroscopic properties of rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) type phosphate  

Microsoft Academic Search

The excitation spectra of pure and rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) in the vacuum ultraviolet (VUV) regions are investigated. The results indicate that these samples show strong absorption in the VUV range. The band ranging from 130 to 160 nm is due to the absorption band of host lattice or PO4 groups; the

Zhi-Jun Zhang; Hao-Hong Chen; Xin-Xin Yang; Jing-Tai Zhao; Guo-Bin Zhang; Chao-Shu Shi

2008-01-01

154

Red, Green, and Blue Light Through Cooperative UpConversion in Sol-Gel Thin Films Made With Yb0.80La0.15Tb0.05F3 and Yb0.80La0.15Eu0.05F3 Nanoparticles  

Microsoft Academic Search

Silica and zirconium dioxide sol-gel thin films made with Yb0.80La0.15Tb0.05F3 or Yb 0.80La0.15Eu0.05F3 nanoparticles are reported. Bright blue (413 and 435 nm), green (545 nm), and red (585 and 625 nm) emissions are produced from Tb3+ ions through cooperative up-conversion of 980 nm light. Similarly, red (591 and 612 nm) emission is generated from Eu3+ ions. These up-convertors may find

Sri Sivakumar

2007-01-01

155

The size confinement effect for Ln3+ (Ln = Tm or Eu) concentration quenching and energy transfer in Y2O3 nanocrystals.  

PubMed

Y2O3:Ln (Ln = Tm or Eu) nano-powders with different particle sizes and various doping concentrations were prepared by using a combustion method. The bulk powders doped with the same concentrations were obtained by annealing the nano-powders at high temperatures. Emission spectra of the phosphors were measured. The crystal structure and morphology of the phosphors were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy), respectively. The concentration quenching of luminescent centers and energy transfer between luminescent centers in Y2O3:Ln nanocrystal powders were investigated. It is found that the behavior of luminescent concentration quenching for Eu3+ 5D0 --> 7F2 in nano-powders is similar to that in bulk powders. On the contrary, the quenching concentration for Tm3+ 1D2 --> 3H4 is distinctly higher than that in bulk powders. This owes to the size confinement effect which will restrain the electric dipole-dipole interaction as a long-rang interaction (e.g., energy transfer between Tm3+ ions), and will hardly affect the exchange interaction which is a short-rang interaction (e.g., energy transfer between Eu3+ ions). PMID:24734659

Wang, Changwen; Meng, Qingyu

2014-05-01

156

Vacuum ultraviolet spectroscopic properties of rare earth (RE=Ce,Tb,Eu,Tm,Sm)-doped hexagonal KCaGd(PO{sub 4}){sub 2} phosphate  

SciTech Connect

Hexagonal KCaGd(PO{sub 4}){sub 2}:RE{sup 3+} (RE=Ce,Tb,Eu,Tm,Sm) were synthesized by coprecipitation method and their vacuum ultraviolet-ultraviolet (VUV-UV) spectroscopic properties were investigated. The bands at about 165 nm in the VUV excitation spectra are attributed to the host lattice absorptions. For Ce{sup 3+}-doped samples, the bands at 207, 256, 275, and 320 nm are assigned to the 4f-5d transitions of Ce{sup 3+} in KCaGd(PO{sub 4}){sub 2}. For Tb{sup 3+}-doped sample, the bands at 203 and 222 nm are related to the 4f-5d spin-allowed transitions. For Eu{sup 3+}-doped sample, the O{sup 2-}-Eu{sup 3+} charge-transfer band (CTB) at 229 nm is observed, and the fine emission spectrum of Eu{sup 3+} indicates that Eu{sup 3+} ions prefer to occupy Gd{sup 3+} or Ca{sup 2+} sites in the host lattice. For Tm{sup 3+}- and Sm{sup 3+}-doped samples, the O{sup 2-}-Tm{sup 3+} and O{sup 2-}-Sm{sup 3+} CTBs are observed to be at 176 and 186 nm, respectively. From the standpoints of the absorption band, color purity, and luminescent intensity, Tb{sup 3+}-doped KCaGd(PO{sub 4}){sub 2} is a potential candidate for 172 nm excited green plasma display phosphors.

Zhang, Z. J.; Yuan, J. L.; Duan, C. J.; Xiong, D. B.; Chen, H. H.; Zhao, J. T.; Zhang, G. B.; Shi, C. S. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China) and Graduate School of Chinese Academy of Science, Beijing 100039 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Heifei 230026 (China)

2007-11-01

157

Far-IR spectra of magnons, crystal field transitions, and phonons in hexagonal REMnO3 (RE=Er, Tm, Yb, Lu) single crystals  

NASA Astrophysics Data System (ADS)

Far-IR spectra of hexagonal REMnO3 (RE=Er, Tm, Yb, Lu) single crystals have been studied between T=1.6 K and 300 K using transmission in high magnetic field and rotating analyzer ellipsometry. The symmetry of the IR optical phonons and their oscillator strengths were determined for compounds with different RE ions. The temperature dependence of the phonon frequencies revealed a strong spin-phonon interaction in the temperature range below TN˜70 K. The effective g-factors have been determined for the AFM resonances and crystal field transitions using external magnetic fields up to 10 T. The frequency of the AFM resonances around 50 cm-1 increases systematically with a decrease of the RE ion radius. The observed effects are analyzed taking into account main magnetic interactions in the system including exchange of the Mn^3+ spins with RE^3+ paramagnetic moments. The magnetic ordering of RE ions was observed at low temperatures T<3.5 K and in strong magnetic fields.

Standard, E. C.; Stanislavchuk, T. N.; Basistyy, R.; Sirenko, A. A.; Kang, T. D.; Lee, N.; Cheong, S.-W.

2012-02-01

158

Tunnel-diode Resonator Spectroscopy of Quantum Levels in Cr12Ln4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) Magnetic Molecules  

NASA Astrophysics Data System (ADS)

The differential magnetic susceptibility for a series of Cr12Ln4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) magnetic molecules was measured in static (up to 16 T) and pulsed (up to 45 T) magnetic fields using a rf tunnel-diode resonator (TDR). At low temperatures, the behavior of these finite spin systems is governed by discrete energy spectra of the individual molecules. In magnetic field, low-energy quantum levels Zeeman-split, crossing at field values where magnetization exhibits a step corresponding to switching between different spin states. In high fields, we detect multiple level crossings which allow for a detailed mapping of the energy diagram. We then perform quantum Monte Carlo (QMC) using a Heisenberg Hamiltonian with three adjustable exchange constants whose values are chosen so as to optimize agreement with the experimental energy spectrum. The variations in results for the studied molecules are correlated to the magnetic properties of the lanthanide ions.

Yeninas, Steven; Luban, Marshall; Prozorov, Ruslan; Coniglio, William A.; Agosta, Charles C.; Engelhardt, Larry; Timco, Grigore A.; Winnpenny, Richard E. P.

2011-03-01

159

Solvothermal synthesis and luminescence properties of NaYF4:Ln3+ (Eu3+, Tb3+, Yb3+/Er3+) nano- and microstructures  

NASA Astrophysics Data System (ADS)

NaYF4 and NaYF4 (Eu3+, Tb3+, Yb3+/Er3+) nano- and microstructures were successfully synthesized through a facile and effective polyol-mediated route with ethylene glycol (EG) as solvent. The factors including the molar ratio of F-/Y3+, reaction temperature and reaction time were well studied in the influences on size, morphology and phase transition of samples. The experimental results indicate that the F-/Y3+ ratio and reaction temperature play key roles in crystal phase and morphology of the product. Higher molar ratio of F-/Y3+ and higher temperature as well as longer reaction time facilitate ? cubic structure-to-? hexagonal structure phase transition, which behaves as a dissolution-recrystallization transformation process. Photoluminescence measurements demonstrated that the as-prepared ?-NaYF4 is one good up- and down-conversion luminescent host material.

Qu, Xuesong; Pan, Guohui; Yang, Hyun Kyoung; Chen, Yeqing; Chung, Jong Won; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun

2012-05-01

160

Crystal field energy levels of Eu3+ and Yb3+ in the C2 and S6 sites of the cubic C-type R2 O3  

NASA Astrophysics Data System (ADS)

In the cubic C-type rare-earth (R) sesquioxides, C-R2 O3, the trivalent R ions (R3+) occupy two different crystallographic sites with S6 and C2 symmetries. The R ions in the C2 lattice site have been studied intensively whereas the properties of the R3+ ions in the S6 site are largely unknown or the data are contradictory. Based on the spectroscopic data reinterpreted by a phenomenological crystal field (cf) analysis a new interpretation was obtained for the energy level scheme of the Eu3+ ions in the S6 site of C-R2 O3. The cf parameters obtained were then used to predict the energy level scheme of the Yb3+ ion in the same host lattices. In the prediction, the evolution of the cf parameters along the R series studied earlier in the R oxide and garnet systems was used. The relationship between the cf strength parameter and the overall splitting of the 2S+1 L J levels as well as the relationship between the barycentres of the free ion levels were used, also, to reinterpret the energy level scheme of the Yb3+ ion in the C2 site of C-Y2 O3.

Antic-Fidancev, Elisabeth; Hölsä, Jorma; Lastusaari, Mika

2003-02-01

161

New high pressure rare earth tantalates RExTa2O5+1.5x (RE=La, Eu, Yb)  

NASA Astrophysics Data System (ADS)

Rare earth tantalates La0.075Ta2O5.113, Eu0.089Ta2O5.134 and Yb0.051Ta2O5.077 have been prepared by solid state reaction at P=7.0 GPa and T=1050-1100 °C and studied by X-ray diffraction, thermal analysis and electron microscopy. Low hydrated amorphous tantalum, lanthanum, europium and ytterbium hydroxides were used as starting materials. Aqueous as well as anhydrous compounds were obtained. Title tantalates are crystallized in the structure type of F-Ta2O5 [Zibrov et al. Russ. J. Inorg. Chem. 48 (2003) 464-471] [5]. The structure was refined by the Rietveld method from X-ray powder diffractometer data: La0.075Ta2O5.113, a=10.5099(2), b=7.2679(1), c=6.9765(1) Å, V=532.90(1) Å3, Z=6, space group Ibam; Eu0.089Ta2O5.134, a=10.4182(3), b=7.2685(1), c=6.9832(1) Å, V=528.80(2) Å3, Z=6, space group Ibam; Yb0.051Ta2O5.077, a=10.4557(2), b=7.3853(1), c=6.8923(1) Å, V=532.21(1) Å3, Z=6, space group Ibam. RE atoms do not replace the tantalum in its positions but the only water in the channels of the structure. Highly charged cations RE+3 compress the unit cell so that its volume becomes less than that of F-Ta2O5. Significant decrease of the unit cell volume after water removal from the structure is possible due to the puckering of pentagonal bipyramid layers and change of the corrugation angle in the layer.

Zibrov, Igor P.; Filonenko, Vladimir P.; Zakharov, Nikolai D.; Werner, Peter; Drobot, Dmitrii V.; Nikishina, Elena E.; Lebedeva, Elena N.

2013-07-01

162

Up-conversion emission tuning in triply-doped Yb3+/Tm3+/Er3+ novel fluoro-phosphate glass and glass-ceramics  

NASA Astrophysics Data System (ADS)

New Yb3+, Er3+ and Tm3+ triply doped fluoro-phosphate glasses belonging to the system NaPO3-YF3-BaF2-CaF2 have been prepared by the classical melt-casting technique. Glasses containing up to 10 wt.% of rare-earth ions fluorides have been obtained and characterized by using differential scanning calorimetry (DSC), UV-visible-near-infrared spectroscopy and up-conversion emission spectroscopy under excitation with a 975 nm laser diode. Transparent and optically homogeneous glass-ceramics have been reproducibly obtained by appropriate heat treatment in view to manage the red, green and blue emissions upon 975 nm laser excitation. According to the applied thermal heat-treatment, a large enhancement of intensity of the up-conversion emission - from 10 to 160 times higher - has been achieved in the glassceramics compared to that of glasses, suggesting incorporation of the rare-earth ions into the crystalline phase. Furthermore, a large range of color rendering has been observed in these materials by controlling the laser excitation power and material crystallization rate. Time-resolved luminescence experiments as well as X-ray diffractometry and scanning electron microscopy techniques have been employed in order to understand and correlate the multicolor emission changes to the crystallization behavior of this material. A progressive phase transformation of the fluorite-type CaF2-based nanocrystals initially generated was observed along with increasing heat-treatment time, thus modifying the rare earth ions spectroscopic features.

Ledemi, Yannick; Trudel, Andrée.-Anne; Rivera, Victor A. G.; Messaddeq, Younes

2014-03-01

163

Structure, enhancement and white luminescence of multifunctional Lu6O5F8:20%Yb3+,1%Er3+(Tm3+) nanoparticles via further doping with Li+ under different excitation sources  

NASA Astrophysics Data System (ADS)

A series of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles with average size from 20 to 320 nm upon increasing Li+ concentration were prepared by a coprecipitation method. The detailed crystal structure of Lu6O5F8 as a new matrix is firstly analysed via retrieved refinement of the powder X-ray diffraction (XRD). In addition, the corresponding Powder Diffraction File card information was also obtained through indexing the XRD pattern of the host. Upconversion under excitation at 980 nm, downconversion with Xe lamp as excitation source and cathodoluminescence properties of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles were compared and studied. It is worthwhile pointing out that according to the effects of Li+ on emission intensity ratio, white UC emission was achieved in the Lu6O5F8:6%Yb3+,0.3%Er3+,0.4%Tm3+,5%Li+ compared to Li+ free sample with the same activator concentration. The reasons behind this behavior were presented and discussed. All in all, Li+ ion would be a wonderful luminescence intensifier for lanthanide ions, and the multifunctional lanthanide ion-doped Lu6O5F8 nanoparticles have potential application in photoluminescence areas and field emission display devices.A series of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles with average size from 20 to 320 nm upon increasing Li+ concentration were prepared by a coprecipitation method. The detailed crystal structure of Lu6O5F8 as a new matrix is firstly analysed via retrieved refinement of the powder X-ray diffraction (XRD). In addition, the corresponding Powder Diffraction File card information was also obtained through indexing the XRD pattern of the host. Upconversion under excitation at 980 nm, downconversion with Xe lamp as excitation source and cathodoluminescence properties of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles were compared and studied. It is worthwhile pointing out that according to the effects of Li+ on emission intensity ratio, white UC emission was achieved in the Lu6O5F8:6%Yb3+,0.3%Er3+,0.4%Tm3+,5%Li+ compared to Li+ free sample with the same activator concentration. The reasons behind this behavior were presented and discussed. All in all, Li+ ion would be a wonderful luminescence intensifier for lanthanide ions, and the multifunctional lanthanide ion-doped Lu6O5F8 nanoparticles have potential application in photoluminescence areas and field emission display devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33577h

Guo, Linna; Wang, Yuhua; Wang, Yanzhao; Zhang, Jia; Dong, Pengyu; Zeng, Wei

2013-02-01

164

Crystal growth, structure determination, and optical properties of new potassium-rare-earth silicates K 3RESi 2O 7 ( RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)  

NASA Astrophysics Data System (ADS)

Single crystals of K 3RESi 2O 7 ( RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K 3RESi 2O 7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K 3LuSi 2O 7, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K 3LuSi 2O 7 crystallizes in space group P6 3/ mmc with a=5.71160(10) Å and c=13.8883(6) Å. The structures containing the remaining rare earths crystallize in the space group P6 3/ mcm with the lattice parameters of a=9.9359(2) Å, c=14.4295(4) Å, (K 3GdSi 2O 7); a=9.88730(10) Å, c=14.3856(3) Å, (K 3TbSi 2O 7); a=9.8673(2) Å, c=14.3572(4) Å, (K 3DySi 2O 7); a=9.8408(3) Å, c=14.3206(6) Å, (K 3HoSi 2O 7); a=9.82120(10) Å, c=14.2986(2) Å, (K 3ErSi 2O 7); a=9.80200(10) Å, c=14.2863(4) Å, (K 3TmSi 2O 7); a=9.78190(10) Å, c=14.2401(3) Å, (K 3YbSi 2O 7). The optical properties of the silicates were investigated and K 3TbSi 2O 7 was found to fluoresce in the visible.

Vidican, Ioana; Smith, Mark D.; zur Loye, Hans-Conrad

2003-02-01

165

Electrochemical and spectroscopic investigation of Ln3+ (Ln = Sm, Eu, and Yb) solvation in bis(trifluoromethylsulfonyl)imide-based ionic liquids and coordination by N,N,N',N'-tetraoctyl-3-oxa-pentane diamide (TODGA) and chloride.  

PubMed

The electrochemistry and electronic absorption spectroscopy of samarium, europium, and ytterbium were investigated in the 1-(1-butyl)trimethylammonium bis(trifluoromethylsulfonyl)imide (BuMe3NTf2N) and 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyroTf2N) ionic liquids and in these solvents containing the neutral tridentate ligand N,N,N',N'-tetraoctyl-3-oxo-pentane diamide (TODGA) and the anionic hard ligand chloride. Lanthanide ions were introduced into the ionic liquids by controlled potential oxidation of the respective metals to yield solutions containing Eu(2+), Sm(3+), and Yb(3+), and it was possible to cycle between Eu(2+) and Eu(3+) as well as Yb(3+) and Yb(2+) using controlled potential electrolysis. Electronic absorption spectroscopy suggested that the Ln(3+) species are weakly solvated by Tf2N(-) anions as [Ln(Tf2N)x]((x-3)-) in the neat ILs. The quasireversible Ln(3+/2+) couples of all three elements were readily accessible in these ILs, but Sm(2+) was only stable on the voltammetric time scale. Addition of TODGA to [Ln(Tf2N)x]((x-3)-) solutions produces 3:1 complexes with Eu(3+) and Sm(3+) but only a 2:1 complex with the smaller Yb(3+) ion. Depending on the temperature, addition of Cl(-) to solutions of [Ln(Tf2N)x]((x-3)-) induces precipitation of LnCl3(s) when the mole ratio mCl(-)/mLn(3+) ? 3. However, when mCl(-)/mLn(3+) > 3, these precipitates redissolve to form the octahedral chloride complexes, [LnCl6](3-). PMID:23439132

Pan, Yunfeng; Hussey, Charles L

2013-03-18

166

Syntheses and crystal structures of anhydrous Ln(hfac)3(monoglyme). Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Er, Tm.  

PubMed

The crystal structures of a broad series of anhydrous Ln(hfac)(3)(monoglyme) complexes, prepared in moderate to high yield, are presented: hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-; Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Er, Tm. This study contradicts the general assumption that monoglyme is too small a polyether to act as a partitioning agent displacing coordinated water on the larger lanthanide(III) ions. The structures of an intermediate La(hfac)(3)(monoglyme)(2) species and the hydrated Ce(hfac)(3)(monoglyme)(H(2)O) species are also included. The crystallographic evidence presented herein is supplemented by other characterization techniques (melting point, IR, etc.) and trends are delineated. PMID:22130475

Fatila, Elisabeth M; Hetherington, Erin E; Jennings, Michael; Lough, Alan J; Preuss, Kathryn E

2012-01-28

167

One-pot solvothermal synthesis of uniform layer-by-layer self-assembled ultrathin hexagonal Gd2O2S nanoplates and luminescent properties from single doped Eu3+ and codoped Er3+, Yb3+.  

PubMed

Uniform Gd(2)O(2)S flower-like nano-assemblies were prepared through one-pot mild solvothermal synthesis. The parallel nanoplates are the building blocks, ?3 nm in thickness and 20-30 in diameter. Ethanediamine, the main solvent, plays an important role in dissolving a large amount of sulphur and producing active S(2-) ions, which results in the direct formation of Gd(2)O(2)S. Oleylamine, the capping agent, controls the growth of the plate-like structure. Under UV excitation, the Gd(2)O(2)S:Eu(3+) nano-phosphor shows good red luminescence with a main emission peak at 627 nm. Under 980 nm laser excitation, Gd(2)O(2)S:xYb(3+),1%Er(3+) nano-phosphors exhibit a tuneable emission, shifting from greenish-yellow to orange-yellow, with increasing Yb(3+) content. PMID:23033159

Liu, Jie; Luo, Hongde; Liu, Pujun; Han, Lixian; Zheng, Xiao; Xu, Bo; Yu, Xibin

2012-12-01

168

Laser-diode-excited blue upconversion in Tm3+/Yb3+ -codoped TeO2-Ga2O3-R2O (R=Li, Na, K) glasses.  

PubMed

This paper reports on intense blue upconversion in Tm(3+)/Yb(3+) codoped TeO(2)-Ga(2)O(3)-R(2)O(R=Li, Na, K) glasses upon excitation with commercial available laser diode (LD). Effects of alkali ions on the Raman spectra, thermal stability and spectroscopic properties of the tellurite-gallium glasses have also been investigated. Energy transfer and the involved upconversion mechanisms have been discussed. Intense blue upconversion emission centered at 476 nm along with a weak red emission at 650 nm has been observed upon excitation of 977 nm LD, assigned to the transitions of 1G4-->3H6, and 1G4-->3H4 and/or 3F(2,3)-->3H6 of Tm(3+), respectively. The blue upconversion intensity has a cubelike dependence on incident pump laser power, indicating a three-photon process. However, a quadratic dependence of the 476 nm upconversion intensity on the incident pump laser power has been observed when samples under excitation of 808 nm LD due to a two-photon absorption process. Enhanced upconversion luminescence have been observed with replacing K(+) for Na(+) and Li(+). PMID:17823854

Zhao, Chun; Zhang, Qinyuan; Yang, Gangfeng; Jiang, Zhonghong

2008-01-01

169

NaYF4:Yb,Tm nanocrystals and TiO2 inverse opal composite films: a novel device for upconversion enhancement and solid-based sensing of avidin  

NASA Astrophysics Data System (ADS)

Upconversion luminescence (UCL) detection based on rare-earth doped upconversion nanocrystals (UCNCs) as probes has been proved to exhibit a large anti-Stokes shift, no autofluorescence from biological samples, and no photobleaching. However, it is still a challenge to achieve a stable, reproducible solid-based UCL biosensor because of ineffective UCL of the UCNCs. In this work, we fabricated TiO2 inverse opal photonic crystals (IOPCs)/NaYF4:Yb3+,Tm3+ (Er3+) UCNC composite films, which can tremendously improve the overall UCL of Tm3+ as high as 43-fold. Based on the fluorescence resonance energy transfer (FRET) and the specific interaction between biotin and avidin, a novel solid-based UC biosensor is presented for sensing avidin. This solid-based detection system is convenient for detection, and also can offer two parameters for detecting trace amounts of avidin, namely, the emission intensity and the fluorescence decay time. The sensor has a high sensitivity of 34 pmol-1, a good linear relationship of 0.996 and a low detection limit of 48 pmol. It also exhibits excellent long-time photostability, and the absence of autofluorescence, and thus may have great potential for versatile applications in biodetection.

Xu, Sai; Xu, Wen; Wang, Yunfeng; Zhang, Shuang; Zhu, Yongsheng; Tao, Li; Xia, Lei; Zhou, Pingwei; Song, Hongwei

2014-05-01

170

NaYF4:Yb,Tm nanocrystals and TiO2 inverse opal composite films: a novel device for upconversion enhancement and solid-based sensing of avidin.  

PubMed

Upconversion luminescence (UCL) detection based on rare-earth doped upconversion nanocrystals (UCNCs) as probes has been proved to exhibit a large anti-Stokes shift, no autofluorescence from biological samples, and no photobleaching. However, it is still a challenge to achieve a stable, reproducible solid-based UCL biosensor because of ineffective UCL of the UCNCs. In this work, we fabricated TiO2 inverse opal photonic crystals (IOPCs)/NaYF4:Yb(3+),Tm(3+) (Er(3+)) UCNC composite films, which can tremendously improve the overall UCL of Tm(3+) as high as 43-fold. Based on the fluorescence resonance energy transfer (FRET) and the specific interaction between biotin and avidin, a novel solid-based UC biosensor is presented for sensing avidin. This solid-based detection system is convenient for detection, and also can offer two parameters for detecting trace amounts of avidin, namely, the emission intensity and the fluorescence decay time. The sensor has a high sensitivity of 34 pmol(-1), a good linear relationship of 0.996 and a low detection limit of 48 pmol. It also exhibits excellent long-time photostability, and the absence of autofluorescence, and thus may have great potential for versatile applications in biodetection. PMID:24752220

Xu, Sai; Xu, Wen; Wang, Yunfeng; Zhang, Shuang; Zhu, Yongsheng; Tao, Li; Xia, Lei; Zhou, Pingwei; Song, Hongwei

2014-06-01

171

Photoelectron spectroscopy of lanthanide-silicon cluster anions LnSi(n)(-) (3 Eu, Yb): prospect for magnetic silicon-based clusters.  

PubMed

Photoelectron spectroscopy was utilized to study a variety of LnSi(n)(-) cluster anions (Ln = Yb, Eu, Sm, Gd, Ho, Pr; 3 YbSi(n)(-) and EuSi(n)(-) are nearly identical to each other, while in the other the spectra of GdSi(n)(-), HoSi(n)(-), and PrSi(n)(-) are essentially identical. SmSi(n)(-) clusters exhibit an intermediate behavior with smaller clusters resembling the former category and larger clusters resembling the latter category. In the intermediate size range, 7 EuSi(n)(-)-like systems and the other HoSi(n)(-)-like clusters. The distinction between LnSi(n)(-) categories strongly correlates with the oxidation state of the particular lanthanide as usually found in its compounds. On the basis of this observation, we conclude that, among the Ln-silicon clusters studied herein, Yb, Eu, and in case of Sm, sizes n >or= 10, adopt a nominal +2 oxidation state while Ho, Pr, Gd, and in case of Sm, sizes n

Grubisic, Andrej; Ko, Yeon Jae; Wang, Haopeng; Bowen, Kit H

2009-08-01

172

Evolution of the crystal and magnetic structure of the R2MnRuO7 (R = Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) family of pyrochlore oxides.  

PubMed

The members of the family of pyrochlore oxides with the formula R(2)MnRuO(7) (R = Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) have been synthesized and characterized. Polycrystalline samples were prepared by a soft chemistry procedure involving citrates of the different metal ions, followed by thermal treatments in air or O(2) pressure. The crystallographic and magnetic structures have been analysed from X-ray diffraction (XRD) and neutron powder diffraction (NPD) data, in complement with magnetic measurements; the evolution along the series of the crystallographic parameters (unit-cell parameters, bond distances and angles) is discussed. In R(2)MnRuO(7) pyrochlores, Mn and Ru ions statistically occupy the 16c sites in a cubic unit cell with space group Fd ?3m, which defines an intrinsic frustrated three-dimensional system. In all the cases, the low-temperature NPD data unveils an antiferromagnetic coupling of two subsets of Mn(4+)/Ru(4+) spins, indicating that the magnetic frustration is partially relieved by the random distribution of Mn and Ru over the 16c sites. At lower temperatures there is a polarization of the R(3+) magnetic moments, which also participate in the magnetic structure, when a magnetic rare earth is present. PMID:22669397

Martínez-Coronado, R; Retuerto, M; Fernández, M T; Alonso, J A

2012-07-28

173

(?-NaYbF4:Tm3+)/CaF2 Core/Shell Nanoparticles with Efficient Near-Infrared to Near-Infrared Upconversion for High-Contrast Deep Tissue Bioimaging  

PubMed Central

We describe the development of novel and biocompatible core/shell (?-NaYbF4:Tm3+)/CaF2 nanoparticles which exhibit highly efficient NIRin-NIRout upconversion (UC) for high contrast and deep bioimaging. When excited at ~980 nm, these nanoparticles emit photoluminescence (PL) peaked at ~800 nm. The quantum yield of this UC PL under low power density excitation (~0.3 W/cm2) is 0.6±0.1%. This high UC PL efficiency is realized by suppressing surface quenching effects via hetero-epitaxial growth of a biocompatible CaF2 shell which results in a 35-fold increase in the intensity of UC PL from the core. Small animal whole-body UC PL imaging with exceptional contrast (signal-to-background ratio of 310) is shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles (700 pmol/kg). High-contrast UC PL imaging of deep tissues is also demonstrated, using a nanoparticle-loaded synthetic fibrous mesh wrapped around rat femoral bone, and a cuvette with nanoparticle aqueous dispersion - covered with a 3.2-cm thick animal tissue (pork).

Chen, Guanying; Shen, Jie; Ohulchanskyy, Tymish Y.; Patel, Nayan J.; Kutikov, Artem; Li, Zhipeng; Song, Jie; Pandey, Ravindra K.; Agren, Hans; Prasad, Paras N.; Han, Gang

2012-01-01

174

A systematic study of the oxygen K edge in the cubic and less common monoclinic phases of the rare earth oxides (Ho, Er, Tm, Yb) by electron energy loss spectroscopy  

NASA Astrophysics Data System (ADS)

Transmission electron microscopy and electron energy loss spectroscopy (EELS) were used to distinguish structural details for the cubic and uncommon monoclinic crystal phases of heavy metal rare earth oxide nanoparticles synthesized by a combustion process. Specifically, we systematically examined the EELS oxygen K edge for Ho, Tm, Er, and Yb sesquioxides in both phases. This work presents, to our knowledge, the first EELS study of the monoclinic phase in these materials and the first systematic comparative study between the monoclinic and cubic phases across a range of rare earth sesquioxides. For both phases, we observed the usual double-peak structure of the oxygen K edge typically seen for oxygen atoms tetrahedrally surrounded by metal atoms, but we found the details of the energy loss near-edge structure to differ substantially between the two phases. Our results indicate a greater peak separation for the cubic than for the monoclinic phase. Furthermore, a trend of increasing peak separation with increasing atomic number was also noted for both phases in the series of rare earth oxide nanoparticles. Our results show that the fine structure in EELS can be utilized to determine differences on the nanoscale between the common cubic structure and the less common monoclinic structure.

Harvey, Ashley; Guo, Bing; Kennedy, Ian; Risbud, Subhash; Leppert, Valerie

2006-02-01

175

Novel light-conversion hybrids of SBA-16 functionalized with rare earth (Eu3+, Nd3+, Yb3+) complexes of modified 2-methyl-9-hydroxyphenalenone and 1,10-phenanthroline  

NASA Astrophysics Data System (ADS)

Novel rare earth complex-functionalized mesoporous SBA-16-type hybrid materials are synthesized by the co-condensation of modified 2-methyl-9-hydroxyphenalenone (MHPOSi), from modified 3-(triethoxysilyl)-propyl isocyanate (TEPIC), and tetraethoxysilane (TEOS) in the presence of Pluronic F127 as a template. These inorganic-organic mesoporous hybrids are characterized by FT-IR spectra, small-angle X-ray diffraction (SAXRD), N2 adsorption-desorption measurements, thermal analysis and spectroscopy. Their photophysical properties, which show novel light conversion properties, are discussed in detail. The Eu3+ hybrid system shows ultraviolet excitation and visible emission, and the Nd+ and Yb3+ hybrids exhibit visible excitation and NIR emission.

Gu, Yan-Jing; Yan, Bing; Qiao, Xiao-Fei

2013-03-01

176

Preparation and spectroscopic properties of rare-earth (RE) (RE = Sm, Eu, Tb, Dy, Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) phosphate in vacuum ultraviolet region  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? We report the VUV spectroscopic properties of rare-earth ions in K{sub 2}LnZr(PO{sub 4}){sub 3}. ? The O{sup 2?}-Eu{sup 3+} charge transfer bands at about 220 nm have been observed. ? The 4f–5d spin-allowed and spin-forbidden transitions of Tb{sup 3+} have been observed. ? There is energy transfer between the host and rare-earth activators. -- Abstract: Rare earth (RE = Sm, Eu, Tb, Dy and Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) have been synthesized by solid-state reaction method, and their vacuum ultraviolet (VUV) excitation luminescent characteristics have been investigated. The band in the wavelength range of 130–157 nm and the other one range from 155 to 216 nm with the maximum at about 187 nm in the VUV excitation spectra of these compounds are attributed to the host lattice absorption and O–Zr charge transfer transition, respectively. The charge transfer bands (CTB) of O{sup 2?}-Sm{sup 3+}, O{sup 2?}-Dy{sup 3+} and O{sup 2?}-Tm{sup 3+}, in Sm{sup 3+}, Dy{sup 3+} and Tm{sup 3+}-activated samples, have not been obviously observed probably because the 2p electrons of oxygen are tightly bound to the zirconium ion in the host lattice. For Eu{sup 3+}-activated samples, the relatively weak O{sup 2?}-Eu{sup 3+} CTB at about 220 nm is observed. And for Tb{sup 3+}-activated samples, the bands at 223 and 258 nm are related to the 4f-5d spin-allowed and spin-forbidden transitions of Tb{sup 3+}, respectively. It is observed that there is energy transfer between the host lattice and the luminescent activators (e.g. Eu{sup 3+}, Tb{sup 3+}). From the standpoint of luminescent efficiency, color purity and chemical stability, K{sub 2}GdZr(PO{sub 4}){sub 3}:Sm{sup 3+}, Eu{sup 3+}, Tb{sup 3+} are attractive candidates for novel yellow, red, green-emitting PDP phosphors.

Zhang, Zhi-Jun, E-mail: zhangzj@mail.sic.ac.cn [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China)] [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Lin, Xiao [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China) [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Graduate School of Chinese Academy of Science, Beijing, 100039 (China); Zhao, Jing-Tai [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China)] [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Zhang, Guo-Bin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026 (China)] [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026 (China)

2013-02-15

177

Effect of Lattice Distortions on 90-K Class Superconductors: Y1-xEuxBa2Cu3O7-delta, Yb1-xSmxBa2Cu3O7-delta and Eu(Ba1-xSrx)2Cu3O7-delta  

Microsoft Academic Search

X-ray powder diffraction studies show that an oxygen deficient perovskite structure is preserved in the whole range of x for the Y1-xEuxBa2Cu3O7-delta and Yb1-xSmxBa2Cu3O7-delta system. Resistivity measurements do not show a strong x-dependence of Tc for either system which has the large difference of ionic radius between Y and Eu or Yb and Sm. In contrast, Tc is more strongly

Isao Taguchi

1988-01-01

178

Spectral conversion for solar cell efficiency enhancement using YVO4:Bi3+,Ln3+ (Ln = Dy, Er, Ho, Eu, Sm, and Yb) phosphors  

Microsoft Academic Search

Bi3+–Ln3+ (Ln = Dy, Er, Ho, Eu, and Sm) co-doped YVO4 phosphors are proposed as UV-absorbing luminescent converter candidate to enhance the power conversion efficiency and photochemical stability of dye-sensitized solar cells (DSSCs). The phosphors can efficiently convert UV photons in a broad range from 250 to 400 nm into visible emissions, which can be absorbed by DSSCs. Efficient broadband

X. Y. Huang; J. X. Wang; D. C. Yu; S. Ye; Q. Y. Zhang; X. W. Sun

2011-01-01

179

Spectral conversion for solar cell efficiency enhancement using YVO4:Bi3+,Ln3+ (Ln = Dy, Er, Ho, Eu, Sm, and Yb) phosphors  

Microsoft Academic Search

Bi3+-Ln3+ (Ln = Dy, Er, Ho, Eu, and Sm) co-doped YVO4 phosphors are proposed as UV-absorbing luminescent converter candidate to enhance the power conversion efficiency and photochemical stability of dye-sensitized solar cells (DSSCs). The phosphors can efficiently convert UV photons in a broad range from 250 to 400 nm into visible emissions, which can be absorbed by DSSCs. Efficient broadband

X. Y. Huang; J. X. Wang; D. C. Yu; S. Ye; Q. Y. Zhang; X. W. Sun

2011-01-01

180

Thermal-Neutron-Capture Gamma Rays in Yb170, Yb172, and Yb174  

Microsoft Academic Search

A Ge(Li) detector was used to investigate the gamma spectra following thermal neutron capture in enriched isotope targets of Yb170, Yb172, and Yb174. In addition to capture in these isotopes, gamma lines were identified as resulting from thermal capture in Yb171 and Yb173. The neutron separation energies of Yb171, Yb172, Yb173, Yb174, and Yb175 were found to be 6616, 8023,

A. I. Namenson; J. C. Ritter

1969-01-01

181

tmRDB (tmRNA database)  

PubMed Central

Maintained at the University of Texas Health Science Center at Tyler, Texas, the tmRNA database (tmRDB) is accessible at the URL http://psyche.uthct.edu/dbs/tmRDB/tmRDB.html with mirror sites located at Auburn University, Auburn, Alabama (http://www.ag.auburn.edu/mirror/tmRDB/) and the Bioinformatics Research Center, Aarhus, Denmark (http://www.bioinf.au.dk/tmRDB/). The tmRDB collects and distributes information relevant to the study of tmRNA. In trans-translation, this molecule combines properties of tRNA and mRNA and binds several proteins to form the tmRNP. Related RNPs are likely to be functional in all bacteria. In this release of tmRDB, 186 new entries from 10 bacterial groups for a total of 274 tmRNA sequences have been added. Lists of the tmRNAs and the corresponding tmRNA-encoded tag-peptides are presented in alphabetical and phylogenetic order. The tmRNA sequences are aligned manually, assisted by computational tools, to determine base pairs supported by comparative sequence analysis. The tmRNA alignment, available in a variety of formats, provides the basis for the secondary and tertiary structure of each tmRNA molecule. Three-dimensional models of the tmRNAs and their associated proteins in PDB format give evidence for the recent progress that has been made in the understanding of tmRNP structure and function.

Zwieb, Christian; Gorodkin, Jan; Knudsen, Bjarne; Burks, Jody; Wower, Jacek

2003-01-01

182

Selective Eu(III) Electro?Reduction and Subsequent Separation of Eu(II) from Rare Earths(III) via HDEHP Impregnated Resin  

Microsoft Academic Search

Eu(III) was selectively reduced to Eu(II) at three?dimensional glassy carbon cathode in 0.01 mol · dm hydrochloric acid medium. Eu(III) reduction took place after all the dissolved oxygen was reduced and then proceeded steadily. Separation of Eu(II) from trivalent rare earths (La, Ce, Sm, Gd, Er, Yb) was carried out using a novel impregnated resin based on bis(2?ethylhexy1)phosphoric acid. Eu(II) showed

Ludek Jelinek; Yuezhou Wei; Tsuyoshi Arai; Mikio Kumagai

2007-01-01

183

The peculiar magnetic property evolution along RCu3Mn4O12 (R=Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu): A first-principles study  

NASA Astrophysics Data System (ADS)

Within RCu3Mn4O12 (R=Rare earth), besides the expected ferrimagnetic order of Mn and Cu ions below TC1, R magnetic moments also play an important role at lower temperatures TC2, leading to their peculiar magnetic behavior. By first-principles calculation, we found that along the series from La to Lu, TC1 monotonically increased due to the ionic radius (IR) induced chemical pressure, as experimentally observed, while TC2 is closely related to the atomic radius of R. Additionally, the magnetic anisotropy energy (?Eani) along the series is found to be correlated with the total magnetic moment of R ion.

Liu, Xiaojuan; Lv, Shuhui; Li, Hongping; Meng, Jian

2010-12-01

184

170Yb Mössbauer study of the heavy-electron pnictides YbP, YbAs and YbSb  

Microsoft Academic Search

170Yb Mössbauer measurements on the heavy-electron compounds YbP, YbAs, and YbSb have probed the competition between RKKY exchange interactions and Kondo hybridisation. Magnetic ordering occurs below TN ~ 0.5 K with reduced magnetic moments; the RKKY exchange interaction was measured and found to be much greater than kBTN.

P. Bonville; J. A. Hodges; F. Hulliger; P. Imbert; G. Jéhanno; J. B. Marimon da Cunha; H. R. Ott

1988-01-01

185

Triaxial strongly deformed bands in {sup 160,161}Tm  

SciTech Connect

High-spin states in {sup 160,161}Tm were populated using the {sup 128}Te({sup 37}Cl, 5n and 4n) reactions at a beam energy of 170 MeV. Emitted {gamma} rays were detected in the Gammasphere spectrometer. Two rotational bands with high moments of inertia were discovered, one assigned to {sup 160}Tm, while the other tentatively assigned to {sup 161}Tm. These sequences display features similar to bands observed in neighboring Er, Tm, Yb, and Lu nuclei which have been discussed in terms of triaxial strongly deformed structures. Cranked Nilsson Strutinsky calculations have been performed that predict well-deformed triaxial shapes at high spin in {sup 160,161}Tm.

Teal, C.; Lagergren, K.; Aguilar, A.; Riley, M. A. [Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States); Hartley, D. J. [Department of Physics, U.S. Naval Academy, Annapolis, Maryland 21402 (United States); Simpson, J.; Joss, D. T. [STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Carpenter, M. P.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; Zhu, S. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Garg, U. [Physics Department, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Kondev, F. G. [Nuclear Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Wang, X. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Physics Department, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Ragnarsson, I. [Division of Mathematical Physics, LTH, Lund University, P.O. Box 118, S-22100 Lund (Sweden)

2008-07-15

186

Optical spectroscopy of Yb2 Ti2 O7 and Y2 Ti2 O7 : Yb3+ and crystal-field parameters in rare-earth titanate pyrochlores  

NASA Astrophysics Data System (ADS)

Optical absorption spectra of the Yb2Ti2O7 single crystals and luminescence spectra of the Y2Ti2O7:Yb (1%) polycrystalline samples were registered at temperatures 4.2-300K . These spectra and earlier published data on magnetic properties of Yb3+ ions and on the temperature dependence of the electric field gradient at Yb nuclei in Yb2Ti2O7 were used to analyze the crystal-field parameters in rare-earth titanates with the pyrochlore structure. The self-consistent sets of crystal-field parameters for rare-earth ions in the 16d sites with the D3d symmetry that describe satisfactory all known single-ion magnetic properties and low-energy excitations in R2Ti2O7 crystals ( R=Tb , Ho, Er, Tm, Yb) are presented.

Malkin, B. Z.; Zakirov, A. R.; Popova, M. N.; Klimin, S. A.; Chukalina, E. P.; Antic-Fidancev, E.; Goldner, Ph.; Aschehoug, P.; Dhalenne, G.

2004-08-01

187

Synthesis, structure, and thermally stable luminescence of Eu(2+)-doped Ba2Ln(BO3)2Cl (Ln = Y, Gd and Lu) host compounds.  

PubMed

A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction. The crystal structure and thermally stable luminescence of chloroborate phosphors Ba(2)Ln(BO(3))(2)Cl:Eu(2+) (Ln = Y, Gd, and Lu) have been reported in this paper. X-ray diffraction studies verify the successful isomorphic substitution for Ln(3+) sites in Ba(2)Ln(BO(3))(2)Cl by other smaller trivalent rare earth ions, such as Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. The detailed structure information for Ba(2)Ln(BO(3))(2)Cl (Ln = Y, Gd, and Lu) by Rietveld analysis reveals that they all crystallize in a monoclinic P2(1)/m space group. These compounds display interesting and tunable photoluminescence (PL) properties after Eu(2+)-doping. Ba(2)Ln(BO(3))(2)Cl:Eu(2+) phosphors exhibit bluish-green/greenish-yellow light with peak wavelengths at 526, 548, and 511 nm under 365 UV light excitation for Ba(2)Y(BO(3))(2)Cl:Eu(2+), Ba(2)Gd(BO(3))(2)Cl:Eu(2+), and Ba(2)Lu(BO(3))(2)Cl:Eu(2+), respectively. Furthermore, they possess a high thermal quenching temperature. With the increase of temperature, the emission bands show blue shifts with broadening bandwidths and slightly decreasing emission intensities. It is expected that this series of chloroborate phosphors can be used in white-light UV-LEDs as a good wavelength-conversion phosphor. PMID:21919480

Xia, Zhiguo; Wang, Xiaoming; Wang, Yingxia; Liao, Libing; Jing, Xiping

2011-10-17

188

AFe2As2 (A = Ca, Sr, Ba, Eu) and SrFe2-xTMxAs2 (TM = Mn, Co, Ni): crystal structure, charge doping, magnetism and superconductivity  

Microsoft Academic Search

The electronic structure and physical properties of the pnictide compound families REOFeAs (RE=La, Ce, Pr, Nd, Sm), AFe2As2 (A=Ca, Sr, Ba, Eu), LiFeAs and FeSe are quite similar. Here, we focus on the members of the AFe2As2 family whose sample composition, quality and single-crystal growth are more controllable compared with the other systems. Using first-principles band structure calculations, we focus

Deepa Kasinathan; Alim Ormeci; Katrin Koch; Ulrich Burkhardt; Walter Schnelle; Andreas Leithe-Jasper; Helge Rosner

2009-01-01

189

EU Business  

NSDL National Science Digital Library

EU Business is provided by Europanet. It aims to provide selected business information to the busy business person. Information available at the site includes European Union (EU) law, business developments in Europe, finance and EU programs. The site also keeps track of European Commission proposals and the progress of draft legislation. Users interested in doing business in Europe will find this site a useful guide to facilitate the process.

1998-01-01

190

Amphiphilic silane modified NaYF4:Yb,Er loaded with Eu(TTA)3(TPPO)2 nanoparticles and their multi-functions: dual mode temperature sensing and cell imaging.  

PubMed

Rare-earth upconversion nanophosphors (UCNPs) have become one of the most promising luminescent materials for bio-applications, but their use still meets some limitations by difficulties in obtaining biocompatible UCNPs. To address this problem, we have developed a simple and versatile strategy for converting hydrophobic UCNPs into hydrophilic ones by amphiphilic silane modification with ultrathin thickness at room temperature (RT). In this strategy, the coating layers can also afford the place for loading with Eu(TTA)3(TPPO)2 complex which displays down conversion luminescence (DCL). Due to the UC and DC properties, we achieved the dual mode physiological range temperature sensing and dual mode cell imaging. Such novel nanomaterials offer a new surface modification strategy for the NPs that are formed in the oil phase for bio-applications. PMID:23892394

Chen, Boting; Dong, Biao; Wang, Jing; Zhang, Shuang; Xu, Lin; Yu, Wei; Song, Hongwei

2013-09-21

191

Frustrated antiferromagnet YbAgGe under magnetic fields and pressures  

NASA Astrophysics Data System (ADS)

We present a detailed study of the field (B)- temperature (T) phase diagram under pressures (P) up to 2.7 GPa for the heavy-fermion antiferromagnet YbAgGe that crystallizes in the hexagonal ZrNiAl-type structure with a quasi-kagome lattice of Yb ions. This compound undergoes two magnetic transitions at TM1 = 0.8 K and TM2 = 0.65 K in zero field at ambient pressure. In the ground state, M(B) shows a metamagnetic transition at BM = 4.6 T for the easy magnetization direction B || a. This transition field decreases to 3.3 T as P is increased to 2.2 GPa. At 2.7 GPa, ?(B) exhibits successive transitions at 5.0, 6.0, 7.5, and 9.0 T. On the other hand, for the hard direction B || c, TM increases with applied field in the P range above 0.5 GPa. This increase of TM(B) is opposite to the decrease of TM(B) for a conventional antiferromagnetic phase. These findings suggest that the application of pressure releases in part the magnetic frustration in YbAgGe.

Kubo, Hirokazu; Umeo, Kazunori; Katoh, Kenichi; Ochiai, Akira; Takabatake, Toshiro

2010-01-01

192

Pressure-induced ferromagnetic order in the weak ferromagnet YbRhSb  

NASA Astrophysics Data System (ADS)

YbRhSb has a small spontaneous moment of 0.003 ?B/Yb below Tm1= 2.7 K at ambient pressure. We have studied the pressure effect on the weak ferromagnetism by the measurements of dc magnetization for a single crystal up to 2.5 GPa. With increasing P, Tm1 (P) increases to a maximum value of 3.3 K. For 0.9 < P < 1.5 GPa, another magnetic transition occurs at Tm1 above Tm1, and Tm1(P) has a deep minimum of 2.5 K at PC = 1.7 GPa. For P > 2 GPa, a spontaneous moment of 0.3?B/Yb appears along the orthorhombic c-axis. In the ferromagnetic state above 2 GPa, magnetization curves for B parallel a and B parallel b exhibit sharp metamagnetic transitions at around 1.5 T. The complexity of the magnetic behaviors may be ascribed to the competition between single-ion crystal field anisotropy with easy direction parallel a and inter-site exchange interaction with easy direction parallel c.

Umeo, K.; Kubo, H.; Muro, Y.; Nakamura, F.; Suzuki, T.; Takabatake, T.

2009-03-01

193

Ultraviolet upconversion luminescence of Gd{sup 3+} and Eu{sup 3+} in nano-structured glass ceramics  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Ultraviolet upconversion emissions of Eu{sup 3+} and Gd{sup 3+} are rarely studied. Black-Right-Pointing-Pointer Nanostructured glass ceramic is developed as a host for ultraviolet upconversion. Black-Right-Pointing-Pointer Ultraviolet upconversion signal are found greatly enhanced after crystallization. Black-Right-Pointing-Pointer It is promising for fabricating novel ultraviolet upconversion lasers. -- Abstract: Ultraviolet multiphoton upconversion emissions of Eu{sup 3+} ({sup 5}H{sub 3-7}, {sup 5}G{sub 2-6}, {sup 5}L{sub 6} {yields} {sup 7}F{sub 0}) and Gd{sup 3+} ({sup 6}I{sub J}, {sup 6}P{sub J} {yields} {sup 8}S{sub 7/2}) are studied in the Eu{sup 3+} (or Gd{sup 3+}) doped SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} precursor glasses and glass ceramics containing {beta}-YF{sub 3} nanocrystals, under continuous-wavelength 976 nm laser pumping. It is experimentally demonstrated that energy transfer from Yb{sup 3+} to Tm{sup 3+}, then further to Eu{sup 3+} or Gd{sup 3+} is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of {beta}-YF{sub 3} nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers.

Lin, Hang; Chen, Daqin; Yu, Yunlong; Yang, Anping; Zhang, Rui [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)] [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Wang, Yuansheng, E-mail: yswang@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)] [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

2012-02-15

194

Chemiluminescent Spectra of YbF and YbCl.  

National Technical Information Service (NTIS)

The chemiluminescent spectra of YbF and YbCl are obtained from the reactions of ytterbium with fluorine and ytterbium with chlorine dioxide under beam-gas conditions and in a high-pressure (3 Torr) system. Much more extensive band systems are observed tha...

H. U. Lee R. N. Zare

1977-01-01

195

Separation of Yb as YbSO 4 from the 176 Yb target for production of 177 Lu via the 176 Yb(n, ?) 177 Yb? 177 Lu process  

Microsoft Academic Search

An effective and simple process for the separation of 177Lu from neutron-irradiated Yb targets was developed. Irradiated Yb target was dissolved in H2SO4 solution and after reduction with sodium amalgam Yb was precipitated in the form of YbSO4. From 50 mg of Yb irradiated target only 1 mg Yb remains in solution after precipitation and separation of YbSO4. The overall

A. Bilewicz; K. ?uchowska; B. Barto?

2009-01-01

196

Continuous wave diode pumped Yb:LLF and Yb:NYF lasers  

NASA Astrophysics Data System (ADS)

Experimental and theoretical results of investigation of CW Yb:LiLuF 4 (Yb:LLF) and Yb:Na 4Y 6F 22 (Yb:NYF) lasers under longitudinal diode laser pump are reported. Slope efficiencies of 41%, 58% with 0.21, 0.53 W of output powers were obtained for the Yb:LLF and Yb:NYF lasers, correspondingly. The Yb:NYF laser demonstrated tunability in the region from 1005 to 1061 nm. The mathematical modelling of CW laser operation predicts under optimized laser parameters optical to optical efficiencies of about 55% and 51% for Yb:LLF and Yb:NYF lasers, respectively.

Yasukevich, A. S.; Kisel, V. E.; Kurilchik, S. V.; Grigoriev, S. V.; Kuleshov, N. V.; Gordeev, E. Yu.; Korableva, S. L.; Naumov, A. K.; Semashko, V. V.

2009-11-01

197

The series of rare earth complexes [Ln2Cl6 (?-4,4'-bipy)(py)6], Ln=Y, Pr, Nd, Sm-Yb: a molecular model system for luminescence properties in MOFs based on LnCl3 and 4,4'-bipyridine.  

PubMed

A series of 12 dinuclear complexes [Ln2Cl6(?-4,4'-bipy)(py)6], Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, (1-12, respectively) was synthesized by an anhydrous solvothermal reaction in pyridine. The complexes contain a 4,4'-bipyridine bridge and exhibit a coordination sphere closely related to luminescent lanthanide MOFs based on LnCl3 and 4,4-bipyridine. The dinuclear complexes therefore function as a molecular model system to provide a better understanding of the luminescence mechanisms in the Ln-N-MOFs (?)(2)[Ln2Cl6(4,4'-bipy)3]·2(4,4'-bipy). Accordingly, the luminescence properties of the complexes with Ln=Y, Sm, Eu, Gd, Tb, Dy, (1, 4-8) were determined, showing an antenna effect through a ligand-metal energy transfer. The highest efficiency of luminescence is observed for the terbium-based compound 7 displaying a high quantum yield (QY of 86%). Excitation with UV light reveals typical emission colors of lanthanide-dependent intra 4f-4f-transition emissions in the visible range (Tb(III) : green, Eu(III) : red, Sm(III) : salmon red, Dy(III) : yellow). For the Gd(III)- and Y(III)-containing compounds 6 and 1, blue emission based on triplet phosphorescence is observed. Furthermore, ligand-to-metal charge-transfer (LMCT) states, based on the interaction of Cl(-) with Eu(III), were observed for the Eu(III) compound 5 including energy-transfer processes to the Eu(III) ion. Altogether, the model complexes give further insights into the luminescence of the related MOFs, for example, rationalization of Ln-independent quantum yields in the related MOFs. PMID:24243814

Matthes, Philipp R; Nitsch, Jörn; Kuzmanoski, Ana; Feldmann, Claus; Steffen, Andreas; Marder, Todd B; Müller-Buschbaum, Klaus

2013-12-16

198

Damping in Yb nuclei  

SciTech Connect

In a mixture of three Yb nuclei, we find the rotational damping widths vary from 180 keV at 1.1 MeV {gamma}-ray energy to 290 keV at 1.5 MeV, and the average compound damping widths (or spreading widths) vary from 40 keV at 1.1 MeV {gamma}-ray energy to 60 keV at 1.3 MeV. The simulations also suggest extensive motional narrowing.

Stephens, F.S.; Deleplanque, M.A.; Lee, I.Y.; Ward, D.; Fallon, P.; Cromaz, M.; Macchiavelli, A.O.; Clark, R.M.; Diamond, R.M.; Gorgen, A.

2002-07-01

199

Concentration distribution of Yb 2+ and Yb 3+ ions in YbF 3:CaF 2 crystals  

Microsoft Academic Search

Calcium fluoride crystals doped with YbF3 were grown using the Bridgman technique. The optical absorption spectra reveal the characteristic UV-absorption bands of divalent Ytterbium. The absorption coefficient of divalent Yb is more than ten times higher than that of trivalent Ytterbium. This shows that the developed crystal growth process achieves a good Yb3+–Yb2+ conversion. The concentration distribution of the Yb2+

Irina Nicoara; Nicolae Pecingina-Garjoaba; Octavian Bunoiu

2008-01-01

200

Interplay between crystal electric field and magnetic exchange anisotropies in the heavy-fermion antiferromagnet YbRhSb under pressure  

NASA Astrophysics Data System (ADS)

We report the pressure effect on the magnetic ground state of the heavy-fermion (HF) canted antiferromagnet YbRhSb (orthorhombic ?-TiNiSi-type) by means of magnetization and resistivity measurements using a single crystal. At ambient pressure, this compound undergoes a transition at TM1=2.7 K into a canted antiferromagnetic (AF) state with a small spontaneous moment of 3×10-3?B/Yb. With increasing pressure P above 1 GPa, another magnetic transition occurs at TM2 above TM1, and TM1(P) has a deep minimum of 2.5 K at 1.7 GPa. For P?2 GPa, the canted AF structure changes to a ferromagnetic (FM) one, where a large moment 0.4 ?B/Yb lies in the orthorhombic b-c plane and a metamagnetic transition occurs at B ||a = 1.5 T. This unusual FM state below TM3?4.3 K is ascribed to the balance between the single-ion crystalline electric field (CEF) anisotropy with easy direction ||a and the intersite exchange interaction with easy b-c plane. Furthermore, we have investigated the pressure dependence of TM3 up to 20.4 GPa using electrical resistivity measurements. The structural stability under pressures up to 19 GPa was examined by x-ray diffraction. We find that TM3 above 2.5 GPa steeply increases up to about 7 K, showing a broad maximum and then slightly decreases with increasing pressure above 8 GPa, while the structure remains unchanged. We attribute the enhancement of TM3 above 2.5 GPa to an increase of the CEF anisotropy with respect to magnetic exchange anisotropy. Finally, we compare and discuss the volume dependence of magnetic phase diagram of YbRhSb with the isostructural HF ferromagnet YbNiSn.

Umeo, K.; Yamane, H.; Kubo, H.; Muro, Y.; Nakamura, F.; Suzuki, T.; Takabatake, T.; Sengupta, K.; Forthaus, M. K.; Abd-Elmeguid, M. M.

2012-01-01

201

A dosimetric comparison of {sup 169}Yb versus {sup 192}Ir for HDR prostate brachytherapy  

SciTech Connect

For the purpose of evaluating the use of {sup 169}Yb for prostate High Dose Rate brachytherapy (HDR), a hypothetical {sup 169}Yb source is assumed with the exact same design of the new microSelectron source replacing the {sup 192}Ir active core by pure {sup 169}Yb metal. Monte Carlo simulation is employed for the full dosimetric characterization of both sources and results are compared following the AAPM TG-43 dosimetric formalism. Monte Carlo calculated dosimetry results are incorporated in a commercially available treatment planning system (SWIFT{sup TM}), which features an inverse treatment planning option based on a multiobjective dose optimization engine. The quality of prostate HDR brachytherapy using the real {sup 192}Ir and hypothetical {sup 169}Yb source is compared in a comprehensive analysis of different prostate implants in terms of the multiobjective dose optimization solutions as well as treatment quality indices such as Dose Volume Histograms (DVH) and the Conformal Index (COIN). Given that scattering overcompensates for absorption in intermediate photon energies and distances in the range of interest to prostate HDR brachytherapy, {sup 169}Yb proves at least equivalent to {sup 192}Ir irrespective of prostate volume. This has to be evaluated in view of the shielding requirements for the {sup 169}Yb energies that are minimal relative to that for {sup 192}Ir.

Lymperopoulou, G.; Papagiannis, P.; Sakelliou, L.; Milickovic, N.; Giannouli, S.; Baltas, D. [Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens (Greece); Department of Medical Physics and Engineering, Strahlenklinik, Klinikum Offenbach, 63069 Offenbach (Germany); Pi-Medical Ltd., Research and Development Dept., Gennimata 2 Str., 115 24, Ampelokipoi, Athens (Greece); Department of Medical Physics and Engineering, Strahlenklinik, Klinikum Offenbach, 63069 Offenbach (Germany) and Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens (Greece)

2005-12-15

202

Xeriscape tm Landscaping  

Microsoft Academic Search

Xeriscape tm landscaping offers an approach for limiting water use in gardening. Xeriscape techniques will become increasingly important as communities cope with drought and dwindling water supplies. This paper introduces the subject and provides an annotated list of information sources.

Beth Clewis

1992-01-01

203

Phase and Size Controllable Synthesis of NaYbF4 Nanocrystals in Oleic Acid/ Ionic Liquid Two-Phase System for Targeted Fluorescent Imaging of Gastric Cancer  

PubMed Central

Upconversion nanocrystals with small size and strong fluorescent signals own great potential in applications such as biomolecule-labeling, in vivo tracking and molecular imaging. Herein we reported that NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with small size and strong fluorescent signals were controllably synthesized by oleic acid (OA)/ ionic liquid (IL) two-phase system for targeted fluorescent imaging of gastric cancer in vivo. The optimal synthesis condition of NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals by OA/IL two-phase system was established, adding more metal ion such as Na+ ion could facilitate the size control and crystal-phase transition, more importantly, markedly enhancing fluorescent intensity of beta-phase nanocrystals compared with traditional methods. Alpha-phase NaYbF4, 2%Tm upconversion nanocrystals with less than 10nm in diameter and beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with 30 nm or so in diameter and strong fluorescent signals were obtained, these synthesized nanocrystals exhibited very low cytotoxicity. Folic acid-conjugated silica-modified beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals were prepared, could actively target gastric cancer tissues implanted into nude mice in vivo, and realized targeted fluorescent imaging. Folic acid-conjugated silica-modified NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals show great potential in applications such as targeted near infared radiation fluorescent imaging, magnetic resonance imaging and targeted therapy of gastric cancer in the near future.

Pan, Liyuan; He, Meng; Ma, Jiebing; Tang, Wei; Gao, Guo; He, Rong; Su, Haichuan; Cui, Daxiang

2013-01-01

204

Yb:S-FAP lasers  

NASA Astrophysics Data System (ADS)

It has recently been reported that several high power, diode-pumped laser systems have been developed based on crystals of Yb:S-FAP [Yb 3+:Sr 5(PO 4) 3F]. The mercury laser, at Lawrence Livermore National Laboratory, is the most prominent system using Yb:S-FAP and is currently producing 23 J at 5 Hz in a 15 nsec pulse, based on partial activation of the system. In addition, a regenerative amplifier is being developed at Waseda University in Japan and has produced greater than 12 mJ with high beam quality at 50 Hz repetition rate. Q-Peak has demonstrated 16 mJ of maximum energy/output pulse in a multi-pass, diode side-pumped amplifier and ELSA in France is implementing Yb:S-FAP in a 985 nm pump for an EDFA, producing 250 mW. Growth of high optical quality crystals of Yb:S-FAP is a challenge due to multiple crystalline defects. However, at this time, a growth process has been developed to produce high quality 3.5 cm diameter Yb:S-FAP crystals and a process is under development for producing 6.5 cm diameter crystals.

Schaffers, Kathleen I.

2004-09-01

205

Magnetic and Moessbauer studies on rare-earth-containing Heusler alloys Pd/sub 2/RSn (R = Tb--Yb)  

SciTech Connect

Magnetic susceptibility and /sup 119/Sn Moessbauer studies have been carried out on a new series of rare-earth-containing Heusler alloys having the formula Pd/sub 2/RSn (R = Tb--Yb). The Tm and Yb compounds in this series along with Lu, Sc, and Y compounds are superconducting. The magnetic susceptibility of Pd/sub 2/TmSn and Pd/sub 2/YbSn deviates from the Curie-Weiss behavior at low temperatures indicating that crystalline electric field effects are appreciable. Analysis of the magnetic susceptibility data in terms of crystalline electric fields shows that the ground state of the Tm/sup 3 +/ ion is nonmagnetic which, therefore, does not affect the superconducting state. The susceptibility of Yb/sup 3 +/ ions at low temperatures is also reduced from the free-ion value due to the crystalline electric field interaction. The Tb- and Dy-containing compounds order antiferromagnetically with Neel temperatures of 9 and 15 K, respectively, while Er- and Ho-containing compounds are paramagnetic down to 1.4 K. The hyperfine field at the Sn site in Pd/sub 2/TbSn is about 50 kOe but is only about 10 kOe in Pd/sub 2/DySn at 4.2 K.

Malik, S.K.; Umarji, A.M.; Shenoy, G.K.

1985-06-01

206

1 W single-frequency Tm-doped ZBLAN fiber MOPA around 810 nm.  

PubMed

We demonstrate a tunable narrow-linewidth fiber MOPA system around 810 nm for the light source of the Sr optical lattice clock. The coherent cw light source with a wavelength of 813.42 nm was generated by a combination of a narrow linewidth external-cavity laser diode and a Tm-doped ZBLAN fiber amplifier, which was upconversion-pumped by an Yb-doped fiber laser at 1064 nm. The maximum output power of 1.1 W was obtained with the launched power of 17 W, which is the highest power obtained from a Tm-doped fiber amplifier ever reported. PMID:24686708

Kohno, Kenta; Takeuchi, Yu-ichi; Kitamura, Toshiyuki; Nakagawa, Ken'ichi; Ueda, Ken-ichi; Musha, Mitsuru

2014-04-01

207

Characterization of quasiparticle states at and beyond stability in ytterbium isotopes: Spectroscopy of 175Yb, 176Yb and 177Yb  

NASA Astrophysics Data System (ADS)

Excited states in 175Yb, 176Yb and 177Yb were populated via the bombardment of a 176Yb target with a 750 MeV 136Xe beam. Gamma-ray decays from these states were measured with the AFRODITE multi-detector spectrometer. The rotational band previously assigned to the ground state of 177Yb has been reassigned to the first-excited state of 175Yb. A new rotational band based on the ground state of 177Yb is presented, and the band based on the K? = 4- two-quasiparticle state in 176Yb has been identified. Also a candidate for the rotational band based on the K? = 8-, T1/2 = 11.4(3) s two-quasiparticle state in 176Yb has been found. Comparisons of gK values derived from in-band branching ratios are consistent with the ?9/2+[624] assignment to the ground state of 177Yb, the ?2{9/2+[624] ? 1/2-[510]} assignment to the K? = 4- state and with the ?2{9/2+[624] ? 7/2-[514]} assignment to the K? = 8- metastable excited state in 176Yb.

Ncapayi, N. J.; Mullins, S. M.; Benatar, M.; Gueorgueiva, E.; Lawrie, J. J.; Mabala, G. K.; Mukherjee, S.; Murray, S. H. T.; Mutshena, K. P.; Newman, R. T.; Sharpey-Schafer, J. F.; Smit, F. D.; Vymers, P.

2005-11-01

208

Mossbauer Studies Of 170Yb in Several Paramagnetic Salts.  

National Technical Information Service (NTIS)

Mossbauer effect studies of the 84 keV (2+ to O+) transition of 170Yb were performed in several paramagnetic salts; Yb2O3, YbCl3, YbF3, Yb3Ga5O12, Yb2(SO4)3.8H2O, Yb(NO3)3.6H2O and ytterbium acetate. Unlike in dysprosium salts, a vast variety of paramagne...

I. Nowik S. Ofer

1968-01-01

209

Broadband near ultra violet sensitization of 1 ?m luminescence in Yb3+-doped CeO2 crystal  

NASA Astrophysics Data System (ADS)

Broadband spectral modification of near ultra violet (UV) light to infra-red (IR) light is investigated in Yb3+-doped CeO2 polycrystalline ceramics sintered in different atmospheres (air, oxygen, and 95%N2-5%H2). The intense Yb3+ photoluminescence (PL) peaked at 970 nm was observed by the UV excitation at around 390 nm in the samples except those sintered under N2-H2. A broad photoluminescence excitation (PLE) band of Yb3+ luminescence peaked at 390 nm corresponds to the absorption band and the photocurrent excitation band in the non-doped CeO2 crystal, which are also in accordance with the PLE band of Eu3+ luminescence in the Eu3+-doped CeO2. Judging from these results, the PLE band is attributed to the charge transfer (CT) band from O2- to Ce4+, but not to the CT from O2- to Yb3+. From the sintering atmosphere dependence of the PL and PLE, we found that the oxygen vacancies and Ce3+ impurities are not responsible for the 390 nm-absorption band but they work as a quenching center for the Yb3+ luminescence.

Ueda, Jumpei; Tanabe, Setsuhisa

2011-10-01

210

Yb 3 d photoemission spectra of Yb(Ba 0.8Sr 0.2) 2Cu 3O 7 and YbF 3  

Microsoft Academic Search

We have measured the Yb 3d photoemission spectra of Yb(Ba0.8Sr0.2)2Cu3O7, YbF3 and related Yb oxides. For Yb(Ba0.8Sr0.2)2Cu3O7 with Yb3+ ions, the Yb 3d photoemission spectrum shows a weak satellite due to the 3d94f14L (L denotes a ligand hole) final state configuration at about 6.5 eV below the main peak. For YbF3, such a satellite is not observed.

Hiroyoshi Ishii; K. Jokura; T. Mitsuishi; H. Arai; S. Nakai; H. Kataura; T. Hanyu

1996-01-01

211

The M X-ray absorption of 70Yb  

Microsoft Academic Search

The MV, MIV and MIII absorption edges of Yb in YbF3 and in the metal have been detected and the variation in the absorption coefficient of Yb, in these regions, computed. The MV line absorption of Yb3+ has been studied in detail and shown to be absent for Yb metal. This latter has been cited as evidence supporting the conclusion,

F. H. Combley; E. A. Stewardson; J. E. Wilson

1968-01-01

212

Phase and size controllable synthesis of NaYbF4 nanocrystals in oleic acid/ionic liquid two-phase system for targeted fluorescent imaging of gastric cancer.  

PubMed

Upconversion nanocrystals with small size and strong fluorescent signals own great potential in applications such as biomolecule-labeling, in vivo tracking and molecular imaging. Herein we reported that NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with small size and strong fluorescent signals were controllably synthesized by oleic acid (OA)/ ionic liquid (IL) two-phase system for targeted fluorescent imaging of gastric cancer in vivo. The optimal synthesis condition of NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals by OA/IL two-phase system was established, adding more metal ion such as Na(+) ion could facilitate the size control and crystal-phase transition, more importantly, markedly enhancing fluorescent intensity of beta-phase nanocrystals compared with traditional methods. Alpha-phase NaYbF4, 2%Tm upconversion nanocrystals with less than 10nm in diameter and beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with 30 nm or so in diameter and strong fluorescent signals were obtained, these synthesized nanocrystals exhibited very low cytotoxicity. Folic acid-conjugated silica-modified beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals were prepared, could actively target gastric cancer tissues implanted into nude mice in vivo, and realized targeted fluorescent imaging. Folic acid-conjugated silica-modified NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals show great potential in applications such as targeted near infared radiation fluorescent imaging, magnetic resonance imaging and targeted therapy of gastric cancer in the near future. PMID:23471455

Pan, Liyuan; He, Meng; Ma, Jiebing; Tang, Wei; Gao, Guo; He, Rong; Su, Haichuan; Cui, Daxiang

2013-01-01

213

170Yb Mössbauer study of the YbCd5.7 binary quasi-crystal and related phases  

NASA Astrophysics Data System (ADS)

170Yb Mössbauer spectroscopy has been used to confirm the valence of Yb in the new binary quasi-crystalline YbCd5.7 alloy. Comparison with other phases in the Yb-Cd phase diagram shows that the local environments of the Yb atoms are very similar.

Ryan, D. H.; M, Saleema N.; Gagnon, R.; van Lierop, J.

2001-11-01

214

Facing the Future (TM)  

NSDL National Science Digital Library

Facing the Future(TM) provides educational materials and professional development opportunities for educators that address environmental issues such as population growth, poverty and equity, consumption trends, peace and conflict, health, climate change, and sustainability. These materials include textbooks for students, service learning and action projects, and curriculum units with activities and lesson plans that meet educational standards. The organization's web site provides information on downloading and/or purchasing these materials, information on a featured curriculum unit, news and event announcements, and information on professional development opportunities for in-service and pre-service educators.

215

Growth of YbF 3-doped CaF 2 crystals and characterization of Yb 3+\\/Yb 2+ conversion  

Microsoft Academic Search

Calcium fluoride crystals doped with YbF3 and PbF2-, NaF- and LiF-codoped were grown using the vertical Bridgman method. Transparent, high quality, with various high Yb2+ contents in the as-grown crystals has been obtained using a special procedure. The optical absorption spectra reveal the characteristic ultraviolet (UV) absorption bands of the divalent Yb ions. Influence of the codoping with Pb2+, Li+

Irina Nicoara; Marius Stef; Andreea Pruna

2008-01-01

216

Thermoelectric properties of YbxEu1-xCd2Sb2  

NASA Astrophysics Data System (ADS)

The thermoelectric performance of EuCd2Sb2 and YbCd2Sb2 was improved by mixed cation occupation. The composition, structure, and thermoelectric properties of YbxEu1-xCd2Sb2 (x=0, 0.5, 0.75, and 1) have been investigated. Polycrystalline samples are prepared by direct reaction of the elements. Thermoelectric properties were investigated after densification of the materials by spark plasma sintering. YbxEu1-xCd2Sb2 crystallizes in the P3m1 space group. The lattice parameters increase with the europium content. These materials show low electrical resistivity, high Seebeck coefficient, and low thermal conductivity together with high carrier concentration and high carrier mobility. ZT values of 0.88 and 0.97 are obtained for Yb0.5Eu0.5Cd2Sb2 and Yb0.75Eu0.25Cd2Sb2 at 650 K, respectively.

Zhang, H.; Fang, L.; Tang, M.-B.; Man, Z. Y.; Chen, H. H.; Yang, X. X.; Baitinger, M.; Grin, Y.; Zhao, J.-T.

2010-11-01

217

A New Yttrium Boride: YB 25  

NASA Astrophysics Data System (ADS)

A new yttrium boride has been found to exist between YB 12and YB 50. A single phase was established at a nominal composition of [B]/[Y]=25.5-26.0. X ray powder diffraction and electron diffraction analyses showed that the new YB 25phase has a monoclinic system with a=0.82842(3) nm, b=1.03203(3) nm, c=0.58570(2) nm, ?=90.402(3)°, and space group I121(No. 5), I1 m1 (No. 8), or I12/ m1 (No. 12). Rare earth elements from Gd to Ho can also form compounds isostructural to YB 25.

Tanaka, T.; Okada, S.; Yu, Y.; Ishizawa, Y.

1997-10-01

218

Analysis of the Petunia TM6 MADS Box Gene Reveals Functional Divergence within the DEF/AP3 Lineage[W  

PubMed Central

Antirrhinum majus DEFICIENS (DEF) and Arabidopsis thaliana APETALA3 (AP3) MADS box proteins are required to specify petal and stamen identity. Sampling of DEF/AP3 homologs revealed two types of DEF/AP3 proteins, euAP3 and TOMATO MADS BOX GENE6 (TM6), within core eudicots, and we show functional divergence in Petunia hybrida euAP3 and TM6 proteins. Petunia DEF (also known as GREEN PETALS [GP]) is expressed mainly in whorls 2 and 3, and its expression pattern remains unchanged in a blind (bl) mutant background, in which the cadastral C-repression function in the perianth is impaired. Petunia TM6 functions as a B-class organ identity protein only in the determination of stamen identity. Atypically, Petunia TM6 is regulated like a C-class rather than a B-class gene, is expressed mainly in whorls 3 and 4, and is repressed by BL in the perianth, thereby preventing involvement in petal development. A promoter comparison between DEF and TM6 indicates an important change in regulatory elements during or after the duplication that resulted in euAP3- and TM6-type genes. Surprisingly, although TM6 normally is not involved in petal development, 35S-driven TM6 expression can restore petal development in a def (gp) mutant background. Finally, we isolated both euAP3 and TM6 genes from seven solanaceous species, suggesting that a dual euAP3/TM6 B-function system might be the rule in the Solanaceae.

Rijpkema, Anneke S.; Royaert, Stefan; Zethof, Jan; van der Weerden, Gerard; Gerats, Tom; Vandenbussche, Michiel

2006-01-01

219

Direct visualization of gastrointestinal tract with lanthanide-doped BaYbF5 upconversion nanoprobes.  

PubMed

Nanoparticulate contrast agents have attracted a great deal of attention along with the rapid development of modern medicine. Here, a binary contrast agent based on PAA modified BaYbF5:Tm nanoparticles for direct visualization of gastrointestinal (GI) tract has been designed and developed via a one-pot solvothermal route. By taking advantages of excellent colloidal stability, low cytotoxicity, and neglectable hemolysis of these well-designed nanoparticles, their feasibility as a multi-modal contrast agent for GI tract was intensively investigated. Significant enhancement of contrast efficacy relative to clinical barium meal and iodine-based contrast agent was evaluated via X-ray imaging and CT imaging in vivo. By doping Tm(3+) ions into these nanoprobes, in vivo NIR-NIR imaging was then demonstrated. Unlike some invasive imaging modalities, non-invasive imaging strategy including X-ray imaging, CT imaging, and UCL imaging for GI tract could extremely reduce the painlessness to patients, effectively facilitate imaging procedure, as well as rationality economize diagnostic time. Critical to clinical applications, long-term toxicity of our contrast agent was additionally investigated in detail, indicating their overall safety. Based on our results, PAA-BaYbF5:Tm nanoparticles were the excellent multi-modal contrast agent to integrate X-ray imaging, CT imaging, and UCL imaging for direct visualization of GI tract with low systemic toxicity. PMID:23849344

Liu, Zhen; Ju, Enguo; Liu, Jianhua; Du, Yingda; Li, Zhengqiang; Yuan, Qinghai; Ren, Jinsong; Qu, Xiaogang

2013-10-01

220

Sites structure and spectroscopic properties of Yb-doped and Yb, Na-codoped CaF 2 laser crystals  

Microsoft Academic Search

For the first time, the effect of Na+ on crystal structure, valence state of Yb ions, spectroscopic properties of YbF3-doped CaF2 system was systematically studied. Na+ can greatly suppress the deoxidization of Yb3+ to Yb2+. Absorption and emission spectra showed codoping Na+ with different Na:Yb ratios can modulate the spectroscopy and photoluminescence properties of Yb3+ ions in CaF2 lattice in

Liangbi Su; Jun Xu; Hongjun Li; Lei Wen; Yueqin Zhu; Zhiwei Zhao; Yongjun Dong; Guoqing Zhou; Jiliang Si

2005-01-01

221

NanoKids(TM)  

NSDL National Science Digital Library

NanoKids(TM) is an education and outreach program for intermediate-level (middle-school) students intended to increase their knowledge of nanotechnology and emerging research and technology in this field, which involves working with objects on the molecular and atomic scale (as small as one-billionth of a meter). Site materials include a series of self-contained lessons accompanied by animated videos and an online workbook for students. There is also a sample test and additional resources for teachers (slide presentations, games, and other materials). The site also offers an overview of the project and its participants, biographical "sketches" of the characters used in the animations, and one-page features that explain the nanometer scale, the countries and scientists involved in nanotechnology, and atoms, molecules, and bondng. Some materials on the site are available in Spanish.

222

Upconversion emission in (Ln,Yb):KLu(WO4)2 nanocrystals for white light generation  

NASA Astrophysics Data System (ADS)

Optical active lanthanides ions in double tungstates exhibit high emission cross section with low concentration quenching. Production of double tungstates nanocrystals doped with lanthanide ions is suitable for applications in white light emitters if high quantum yield is reached. In this work lanthanide doped (Ln:Yb):KLu(WO4)2 nanocrystals (Ln = Er, Tm, Ho) upconversion emission properties have been study after 980 nm diode laser excitation at 14–334 W/cm2. From CIE chromaticity theory a possible mixture weight ratio to obtain a white light emitter powder was predicted. Luminescence under 980 nm of the (Ln:Yb):KLu(WO4)2 nanocrystals was study and decay times under 460 nm was measured. Reduction of the upconversion quantum yield was observed in the case of physical mixture of nanocrystals.

Barrera, E. W.; Pujol, M. C.; Carvajal, J. J.; Mateos, X.; Solé, R.; Massons, J.; Speghini, A.; Bettinelli, M.; Cascales, C.; Aguiló, M.; Díaz, F.

2014-04-01

223

Phase equilibrium and intermediate phases in the Eu-Sb system  

SciTech Connect

Rapid heating rate thermal analysis, X-ray diffraction, fluorescence spectrometry, and differential dissolution method were used to study the high-temperature phase equilibrium in the Eu-Sb system within the composition range between 37 and 96 at% Sb. The techniques were effective in determination of the vapor-solid-liquid equilibrium since intermediate phases except Eu{sub 4}Sb{sub 3} evaporated incongruently after melting. A thermal procedure was developed to determine the liquidus and solidus lines of the T-x diagram. Six stable phases were identified: two phases, EuSb{sub 2} and Eu{sub 4}Sb{sub 3}, melt congruently at 1045{+-}10 deg. C and 1600{+-}15 deg. C, the Eu{sub 2}Sb{sub 3}, Eu{sub 11}Sb{sub 10}, Eu{sub 5}Sb{sub 4}, and Eu{sub 5}Sb{sub 3} phases melt incongruently at 850{+-}8 deg. C, 950{+-}10 deg. C, 1350{+-}15 deg. C, and 1445{+-}15 deg. C, respectively. The exact composition shifting of Sb-rich decomposable phases towards Eu{sub 4}Sb{sub 3}, the most refractory compound, was determined. The topology of the Eu-Sb phase diagram was considered together with that of the Yb-Sb system. - Graphical abstract: The high-temperature range of the T-x phase diagram for the Eu-Sb system. Highlights: > The phase relations in the Eu-Sb system were studied over a large composition and temperature scale. > The liquidus and solidus lines of the T-x diagram were well established using effective techniques. > In the system, six binary phases are stable and they melt incongruently except EuSb{sub 2} and Eu{sub 4}Sb{sub 3}. > Incongruent evaporation was found to be typical of all the phases besides Eu{sub 4}Sb{sub 3}.

Abdusalyamova, M.N. [Institute of Chemistry of Tajik Academy of Sciences, Ajni Str. 299/2, 734063 Dushanbe (Tajikistan); Vasilyeva, I.G., E-mail: kamarz@niic.nsc.ru [Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Lavrentiev Avenue, 3, 630090 Novosibirsk (Russian Federation)

2011-10-15

224

Effects of Yb3+ in Er3+/Yb3+ Codoped Fluorophosphate Glasses  

NASA Astrophysics Data System (ADS)

For the Er3+/Yb3+ codoped fluorophosphate glasses, Judd-Ofelt theory is used to analyse the influence of YbF3 as not a sensitizer but an average component on the spectroscopic properties around 1530 nm emission. The double roles of Yb3+, as a sensitizer and as an average component, are discussed. It is found that Yb3+ as an average component contributes to the increase of fluorescence lifetime, and Yb3+ as a sensitizer has the best sensitization when its concentration is 2.4 mol%.

Liao, Mei-Song; Fang, Yong-Zheng; Hu, Li-li; Zhang, Li-Yan; Xu, Shi-Qing

2007-04-01

225

Structure of YB12 and SCB12.  

National Technical Information Service (NTIS)

Preparation of single crystals of YB12 and ScB12 was carried out and the structure of both compounds was examined. ScB12 was found to be tetragonal with a - 5.22A and c - 7.35A, space group I4/mmm. YB12 was found to be cubic in agreement with earlier repo...

V. I. Matkovich J. Economy R. F. Giese R. B. Barrett

1964-01-01

226

Unconventional T-H Phase Diagram in the Noncentrosymmetric Compound Yb2Fe12P7  

NASA Astrophysics Data System (ADS)

The temperature-(T-)magnetic-field (H) phase diagram for the noncentrosymmetric compound YbFeP, determined from electrical resistivity (?), specific heat (C), and magnetization (M) measurements on single crystal specimens, is reported. This system exhibits a crossover from a magnetically ordered non-Fermi-liquid (NFL) phase at low H to another NFL phase at higher H. The crossover occurs near the value of H where the magnetic ordering temperature (TM) is no longer observable in C(T,H)/T and ?(T,H), but not where TM extrapolates smoothly to T=0K at a possible quantum critical point (QCP). This indicates the occurrence of a quantum phase transition between the two NFL phases. The lack of a clear relationship between the extrapolated QCP and NFL behavior suggests an unconventional route to the NFL ground states.

Baumbach, R. E.; Hamlin, J. J.; Shu, L.; Zocco, D. A.; O'Brien, J. R.; Ho, P.-C.; Maple, M. B.

2010-09-01

227

Gd(3+)-Yb(3+) Exchange Interactions in LiYb(x)Y(1-x)F4 Single Crystals.  

National Technical Information Service (NTIS)

The evaluated Gd(3+) -Yb(3+) exchange interactions over the nearest and the next-nearest neighbors in LiYb(x)Y(1-x)F4 are found to increase in parabolic manner with x, the concentration of Yb(3+) ions. The Gd(3+) -Yb(3+) exchange interactions are sensitiv...

L. E. Misiak

2001-01-01

228

Mercury Removal Performance of Amberlite(TM) GT-73A, Purolite(TM) S-920, Ionac(TM) SR-4 and SIR-200(TM) Resins.  

National Technical Information Service (NTIS)

Testing looked at the mercury removal performance of various resins: Amberlite(TM) GT-73A from Rohn and Haas, Purolite(TM) S-920 from Bro-Tech Corporation, Ionac(TM) SR-4 from Sybron Chemicals, and SIR-200(TM) from Resin Tech. Larger than explained variat...

F. F. Fondeur W. B. Van Pelt S. D. Fink

2002-01-01

229

CaF2:Yb laser ceramics  

NASA Astrophysics Data System (ADS)

CaF2:Yb fluoride laser ceramics, prepared by hot-forming, exhibit the same optical properties as starting single crystals. Slope efficiency of the ?a0.95Yb0.05F2.05 is equal to 35% in the pulsed mode of laser operation. Decrease of ytterbium concentration in CaF2:Yb samples down to 3 mol.% resulted in the essential improvement of ?a0.97Yb0.03F2.03 thermal conductivity from 3.5 to 4.5 W/m K, but slightly decreased (down to 30%) slope efficiency of the samples under both pulsed and CW mode of operation. Alternative hot-pressing synthesis of CaF2:Yb fluoride laser ceramics provided materials with superior mechanical properties (microhardness ? = 3.2 GPa and fracture toughness ?1? = 0.65 ?P? m1/2) in comparison with hot-formed and/or single crystal CaF2:Yb specimens. For the first time, lasing has been observed for the novel aforementioned hot-pressed CaF2:Yb ceramics.

Akchurin, M. Sh.; Basiev, T. T.; Demidenko, A. A.; Doroshenko, M. E.; Fedorov, P. P.; Garibin, E. A.; Gusev, P. E.; Kuznetsov, S. V.; Krutov, M. A.; Mironov, I. A.; Osiko, V. V.; Popov, P. A.

2013-01-01

230

Yb3+:YAG silica fiber laser.  

PubMed

We demonstrate a compact, room-temperature, cw Yb(3+):Y(3)Al(5)O(12) silica (Yb(3+):YAG silica) fiber laser grown by the codrawing laser-heated pedestal growth technique. A slope efficiency of 76.3% was achieved from a 7 mm Yb(3+):YAG silica fiber, corresponding to an extracted power of nearly 1 W/cm. A laser side-mode suppression ratio of 70 dB was obtained with a 3 dB linewidth of 0.15 nm. Additionally, the propagation loss and emission cross section were determined by analyzing the lasing thresholds and slope efficiencies. PMID:19649096

Lai, Chien-Chih; Huang, Kuang-Yao; Tsai, Hann-Jong; Hsu, Kuang-Yu; Liu, Shih-Kun; Cheng, Ching-Ting; Ji, Kuan-Dong; Ke, Chih-Peng; Lin, Si-Rong; Huang, Sheng-Lung

2009-08-01

231

Anomalies in the Young modulus at structural phase transitions in rare-earth cobaltites RBaCo4O7 (R = Y, Tm-Lu)  

NASA Astrophysics Data System (ADS)

The elastic properties of rare-earth cobaltites RBaCo4O7 (R = Y, Tm-Lu) have been experimentally studied in the temperature range of 80-300 K. The strong softening of the Young modulus ? E( T)/ E 0 ? -(0.1-0.2) of cobaltites with Lu and Yb ions has been revealed, which is due to the instability of the crystal structure upon cooling and is accompanied by an inverse jump at the second-order structural phase transition. The softening of the Young modulus and the jump at the phase transition decrease by an order of magnitude and the transition temperature T s and hysteresis ? T s increase from a compound with Lu to that with Tm. A large softening of the Young modulus at the structural transition in Lu- and Yb cobaltites indicates that the corresponding elastic constant goes to zero, whereas this constant in Tm cobaltite is not a "soft" mode of the phase transition. It has been found that the structural phase transition in Lu- and Yb cobaltites is accompanied by a large absorption maximum at the phase transition point and an additional maximum in the low-temperature phase and absorption anomalies in Tm cobaltite is an order of magnitude smaller.

Kazei, Z. A.; Snegirev, V. V.; Andreenko, A. S.; Kozeeva, L. P.

2011-08-01

232

Efficient blue up-conversion luminescence of Tm3+ ions in transparent oxyfluoride glass ceramics containing Pbx Cd1-x F2 nanocrystals  

NASA Astrophysics Data System (ADS)

Oxyfluoride glasses were developed in the 30SiO2 . 15AlO1.5 . 28PbF2 . 22CdF2 . (4.8 - y)GdF3 . 0.1NdF3 . yYbF3 . 0.1TmF3 (y = 0, 0.1, 0.2, 0.5, 1, 2, 3, 4 and 4.8) composition, in mol%. X-ray diffraction analysis revealed that heat treatments of the oxyfluoride glasses cause the precipitation of (Nd3+, Yb3 +, Tm3+)-doped fluorite-type Pbx Cd1-x F2 nanocrystals of about 17.8 nm diameter in a glass matrix. Very strong blue up-conversion luminescence which can be assigned to the Tm3+ :1 G 4 rightarrow3 H 6 transition under 800 nm excitation was observed in these transparent glass ceramics. The intensity of the blue up-conversion luminescence is strongly dependent on the precipitation of Pbx Cd1-x F2 crystals and the YbF3 concentration. The reasons for the highly efficient Tm3+ up-conversion luminescence are discussed. An energy transfer process and an up-conversion mechanism in the glass and glass ceramics are also proposed.

Qiu, J.; Mukai, A.; Makishima, A.; Kawamoto, Y.

2002-12-01

233

Monodisperse lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm): morphology controlled synthesis, up-conversion luminescence and in vitro cell imaging  

NASA Astrophysics Data System (ADS)

Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb3+, 0.04Er3+ nanospheres is dominated by a single red emission at 660 nm, which falls into the ``optical window'' of biological tissues. The application of YOF: 0.20Yb3+, 0.04Er3+ nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise.Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb3+, 0.04Er3+ nanospheres is dominated by a single red emission at 660 nm, which falls into the ``optical window'' of biological tissues. The application of YOF: 0.20Yb3+, 0.04Er3+ nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise. Electronic supplementary information (ESI) available: The XRD patterns of GdOF, ErOF, Tm(OF)1.93 and YOF obtained after calcinations at 800 °C for 3 h and the corresponding standard data of GdOF, ErOF, Tm(OF)1.93 and YOF. The accurate amounts of Ln3+ and F- for LaOF, GdOF, ErOF and YOF: 0.20Yb3+, 0.04Er3+, respectively. SEM images of the ErOF precursor under different experimental conditions (a) pH = 2, urea/Ln3+ = 66, with LiF; (b) pH = 2, urea/Ln3+ = 66, with KF; (c) pH = 6, urea/Ln3+ = 66, with NaF; (d) pH = 10, urea/Ln3+ = 66, with NaF; (e) pH = 2, urea/Ln3+ = 80, with NaF and (f) pH = 2, urea/Ln3+ = 100, with NaF. See DOI: 10.1039/c4nr00384e

Zhang, Yang; Li, Xuejiao; Hou, Zhiyao; Lin, Jun

2014-05-01

234

Structure and magnetic properties of sulfides of the type Cd RE2S 4 and Mg(Gd xYb 1- x) 2S 4  

NASA Astrophysics Data System (ADS)

Cd RE2S 4 ( RE = Gd, Tb, Dy, Ho, Er, Tm, and Yb) and Mg(Gd xYb 1- x) 2S 4 were prepared by solid-state reactions. All the cadmium-containing compounds are cubic, i.e., the Th 3P 4 structure for Gd, Tb, and Dy and the spinel type for all the others. The first three compounds were deficient in CdS. In the case of the Mg system, for x = 1 the system is cubic Th 3P 4, for x = 0 cubic spinel, and for 0 < x < 1 orthorhombic MnY 2S 4 (Cmc2 1). All the materials studied are paramagnetic above 77 K. Below 77 K in the magnesium family both cubic materials are paramagnetic down to 4.2 K and the orthorhombic materials show magnetic ordering. In the cadmium family all but CdTm 2S 4 show exchange coupling.

Ben-Dor, L.; Shilo, I.

1980-11-01

235

Itinerant and local-moment magnetism in EuCr2As2 single crystals  

NASA Astrophysics Data System (ADS)

We report on the crystal structure, physical properties, and electronic structure calculations for the ternary pnictide compound EuCr2As2. X-ray diffraction studies confirmed that EuCr2As2 crystalizes in the ThCr2Si2-type tetragonal structure (space group I4/mmm). The Eu ions are in a stable divalent state in this compound. Eu moments in EuCr2As2 order magnetically below Tm = 21 K. A sharp increase in the magnetic susceptibility below Tm and the positive value of the paramagnetic Curie temperature obtained from the Curie-Weiss fit suggest dominant ferromagnetic interactions. The heat capacity exhibits a sharp ?-shape anomaly at Tm, confirming the bulk nature of the magnetic transition. The extracted magnetic entropy at the magnetic transition temperature is consistent with the theoretical value Rln(2S +1) for S =7/2 of the Eu2+ ion. The temperature dependence of the electrical resistivity ? (T) shows metallic behavior along with an anomaly at 21 K. In addition, we observe a reasonably large negative magnetoresistance (˜-24%) at lower temperature. Electronic structure calculations for EuCr2As2 reveal a moderately high density of states of Cr-3d orbitals at the Fermi energy, indicating that the nonmagnetic state of Cr is unstable against magnetic order. Our density functional calculations for EuCr2As2 predict a G-type AFM order in the Cr sublattice. The electronic structure calculations suggest a weak interlayer coupling of the Eu moments.

Paramanik, U. B.; Prasad, R.; Geibel, C.; Hossain, Z.

2014-04-01

236

Crystal structures and magnetic properties of novel rare-earth copper sulfides, EuRCuS3 (R = Y, Gd Lu)  

NASA Astrophysics Data System (ADS)

Novel quaternary rare-earth copper sulfides EuRCuS3 (R = Y, Gd-Lu excluding Ho, Er) have been investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, and specific heat measurements. These compounds crystallize in the Eu2CuS3-type structure for R = Y, Gd-Dy and in the KZrCuS3-type structure for R = Tm-Lu. Both EuY CuS3 and EuLuCuS3 show a ferromagnetic transition and the other EuRCuS3 compounds show a ferrimagnetic transition at around 5.0 K.

Wakeshima, Makoto; Furuuchi, Fumito; Hinatsu, Yukio

2004-08-01

237

Optical study of c-f hybridization states in mixed-valent Yb compounds: metallic YbAl 3 vs semiconducting YbB 12  

NASA Astrophysics Data System (ADS)

We have measured the optical conductivity spectra ?( ?) of YbB 12 and YbAl 3, which are typical mixed-valent Yb compounds. The measured ?( ?) spectra in the mid-infrared region are quite similar for the two compounds, with a pronounced peak centered near 0.2 eV. This result demonstrates that the Kondo semiconductor YbB 12 and the highly metallic YbAl 3 share very similar electronic structures near the Fermi level, in spite of their very different transport properties at low temperatures. This observation is discussed in terms of c-f hybridization states in these compounds.

Okamura, H.; Michizawa, T.; Matsunami, M.; Kimura, S.; Nanba, T.; Ebihara, T.; Iga, F.; Takabatake, T.

238

Optical study of c-f hybridization states in mixed-valent Yb compounds: metallic YbAl3 vs semiconducting YbB12  

NASA Astrophysics Data System (ADS)

We have measured the optical conductivity spectra ?(?) of YbB12 and YbAl3, which are typical mixed-valent Yb compounds. The measured ?(?) spectra in the mid-infrared region are quite similar for the two compounds, with a pronounced peak centered near 0.2eV. This result demonstrates that the Kondo semiconductor YbB12 and the highly metallic YbAl3 share very similar electronic structures near the Fermi level, in spite of their very different transport properties at low temperatures. This observation is discussed in terms of c-f hybridization states in these compounds.

Okamura, H.; Michizawa, T.; Matsunami, M.; Kimura, S.; Nanba, T.; Ebihara, T.; Iga, F.; Takabatake, T.

2004-05-01

239

Listening and Legos[TM  

ERIC Educational Resources Information Center

This simple exercise, performed in teams, gives students practice in listening to instructions, particularly when there are restrictions for the communication. The teams compete in a limited amount of time to build a Lego[TM] structure based on the instructions of one team member. Which team listens the best and is most successful?

Morris, Pamela

2012-01-01

240

Optical and spectral characterization of Er 3+/Yb 3+-codoped NAT ceramics  

NASA Astrophysics Data System (ADS)

Er 3+/Yb 3+-codoped aluminum oxide (Al 2O 3) modified tellurite ceramics have been prepared by high-temperature melting. Judd-Ofelt parameters of Eu 3+, which was introduced in 15%Na 2O-15%Al 2O 3-70%TeO 2 (NAT) ceramic system as a probe, present a medium asymmetry and covalence environment around rare-earth ions. Efficient 551 nm green and 668 nm red two-photon pumped upconversion fluorescence and strong 1.533 ?m infrared radiation were observed and recorded in the Er 3+/Yb 3+-codoped NAT ceramics under the excitation of ?980 nm diode lasers. For 1.533 ?m near-infrared emission, the maximum stimulated emission cross-section was calculated to be 6.61×10 -21 cm 2, and the ordinary exhibition referring to tellurite glass system is due to the lowering of refractive index, which is caused by the abundance of Al 2O 3 composition. Efficient visible upconversion and infrared emissions indicate that Er 3+/Yb 3+-codoped NAT ceramics are promising substrates in developing color light sources, upconversion display devices, infrared sensors and infrared radiation sources.

Wang, N. Q.; Li, X. J.; Pun, E. Y. B.; Lin, H.; Yang, D. L.

2009-05-01

241

Lattice dynamics in the thermoelectric Zintl compound Yb14MnSb11  

NASA Astrophysics Data System (ADS)

The density of phonon states in the thermoelectric material Yb14MnSb11 has been studied first by inelastic neutron scattering and second in an element-specific way by nuclear inelastic x-ray scattering. The low sound velocity of 1880(50) m/s as obtained from the density of phonon states can be identified as an important reason for the low heat transport in this system. The high melting temperature of Yb14MnSb11 contrasts with the low energy of all phonons (<25 meV) and relates to an unusual lack of softening of phonon modes with temperature, when comparing the phonon density of states observed at ambient temperatures and at 1200 K. We have also measured the density of phonon states of the related Eu14MnSb11 compound and of the thermoelectric Zintl phase Zn4Sb3 in order to compare with related thermodynamic properties of Yb14MnSb11 and to elucidate the different mechanisms of the heat conductivity reduction in Zintl phases.

Möchel, A.; Sergueev, I.; Wille, H.-C.; Juranyi, F.; Schober, H.; Schweika, W.; Brown, S. R.; Kauzlarich, S. M.; Hermann, R. P.

2011-11-01

242

EU SmartGrids Framework \\  

Microsoft Academic Search

The IEA World Energy Investment Outlook 2003 states that the electricity sector in the EU has an annual turnover of about $150billion and contributes about 1.5% to EU GDP. Investment in the sector is about $30 billion per year in the EU. Looking ahead, EU Member States will need to invest in excess of one trillion dollars in power infrastructure

M. Chebbo

2007-01-01

243

Applications of TM polarized illumination  

NASA Astrophysics Data System (ADS)

The use of transverse electric (TE) polarization has dominated illumination schemes as selective polarization is used for high-NA patterning. The benefits of TE polarization are clear - the interference of diffracted beams remains absolute at oblique angles. Transverse magnetic (TM) polarization is usually considered less desirable as imaging modulation from interference at large angle falls off rapidly as the 1/cos?. Significant potential remains, however, for the use of TM polarization at large angles when its reflection component is utilized. By controlling the resist/substrate interface reflectivity, high modulation for TM polarization can be maintained for angles up to 90° in the resist. This can potentially impact the design of illumination away from most recent TE-only schemes for oblique imaging angles (high NA). We demonstrate several cases of TM illumination combined with tuned substrate reflectivity for 0.93NA, 1.20NA, and 1.35NA and compare results to TE and unpolarized cases. The goal is to achieve a flat response through polarization at large imaging angles. An additional application of TM illumination is its potential use for double patterning. As double patterning and double exposure approaches are sought in order to meet the needs of 32nm device generations and beyond, materials and process engineering challenges become prohibitive. We have devised a method for frequency doubling in a single exposure using an unconventional means of polarization selection and by making use of the reflective component produced at the photoresist/substrate interface. In doing so, patterns can be deposited into a photoresist film with double density. As an example, using a projection system numerical aperture of 1.20, with water as an immersion fluid, and a conventional polyacrylate 193nm photoresist, pattern resolution at 20nm half-pitch are obtainable (which is 0.125lambda/NA). The process to transfer this geometry into a hardmask layer uses conventional materials, including the photoresist layer and thin film silicon oxide based materials.

Smith, Bruce; Zhou, Jianming; Xie, Peng

2008-03-01

244

Study of encapsulated {sup 170}Tm sources for their potential use in brachytherapy  

SciTech Connect

Purpose: High dose-rate (HDR) brachytherapy is currently performed with {sup 192}Ir sources, and {sup 60}Co has returned recently into clinical use as a source for this kind of cancer treatment. Both radionuclides have mean photon energies high enough to require specific shielded treatment rooms. In recent years, {sup 169}Yb has been explored as an alternative for HDR-brachytherapy implants. Although it has mean photon energy lower than {sup 192}Ir, it still requires extensive shielding to deliver treatment. An alternative radionuclide for brachytherapy is {sup 170}Tm (Z=69) because it has three physical properties adequate for clinical practice: (a) 128.6 day half-life, (b) high specific activity, and (c) mean photon energy of 66.39 keV. The main drawback of this radionuclide is the low photon yield (six photons per 100 electrons emitted). The purpose of this work is to study the dosimetric characteristics of this radionuclide for potential use in HDR-brachytherapy. Methods: The authors have assumed a theoretical {sup 170}Tm cylindrical source encapsulated with stainless steel and typical dimensions taken from the currently available HDR {sup 192}Ir brachytherapy sources. The dose-rate distribution was calculated for this source using the GEANT4 Monte Carlo (MC) code considering both photon and electron {sup 170}Tm spectra. The AAPM TG-43 U1 brachytherapy dosimetry parameters were derived. To study general properties of {sup 170}Tm encapsulated sources, spherical sources encapsulated with stainless steel and platinum were also studied. Moreover, the influence of small variations in the active core and capsule dimensions on the dosimetric characteristics was assessed. Treatment times required for a {sup 170}Tm source were compared to those for {sup 192}Ir and {sup 169}Yb for the same contained activity. Results: Due to the energetic beta spectrum and the large electron yield, the bremsstrahlung contribution to the dose was of the same order of magnitude as from the emitted gammas and characteristic x rays. Moreover, the electron spectrum contribution to the dose was significant up to 4 mm from the source center compared to the photon contribution. The dose-rate constant {Lambda} of the cylindrical source was 1.23 cGy h{sup -1} U{sup -1}. The behavior of the radial dose function showed promise for applications in brachytherapy. Due to the electron spectrum, the anisotropy was large for r<6 mm. Variations in manufacturing tolerances did not significantly influence the final dosimetry data when expressed in cGy h{sup -1} U{sup -1}. For typical capsule dimensions, maximum reference dose rates of about 0.2, 10, and 2 Gy min{sup -1} would then be obtained for {sup 170}Tm, {sup 192}Ir, and {sup 169}Yb, respectively, resulting in treatment times greater than those for HDR {sup 192}Ir brachytherapy. Conclusions: The dosimetric characteristics of source designs exploiting the low photon energy of {sup 170}Tm were studied for potential application in HDR-brachytherapy. Dose-rate distributions were obtained for cylindrical and simplified spherical {sup 170}Tm source designs (stainless steel and platinum capsule materials) using MC calculations. Despite the high activity of {sup 170}Tm, calculated treatment times were much longer than for {sup 192}Ir.

Ballester, Facundo; Granero, Domingo; Perez-Calatayud, Jose; Venselaar, Jack L. M.; Rivard, Mark J. [Department of Atomic, Molecular and Nuclear Physics, University of Valencia, E-46100 Burjassot (Spain) and IFIC, CSIC, University of Valencia, E-46100 Burjassot (Spain); Department of Radiation Oncology, ERESA, Hospital General Universitario, E-46014 Valencia (Spain); Department of Radiation Oncology, La Fe University Hospital, E-46009 Valencia (Spain); Department of Medical Physics, Instituut Verbeeten, Tilburg 5000LA (Netherlands); Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111 (United States)

2010-04-15

245

75 FR 2129 - Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...13625-000] Lock+ TM Hydro Friends Fund XXX, LLC; Notice of Preliminary Permit Application...13, 2009, Lock+ TM Hydro Friends Fund XXX, LLC filed an application, pursuant to...Krouse, Lock+ TM Hydro Friends Fund XXX, LLC, 5090 Richmond Avenue...

2010-01-14

246

Modified LaRC(TM)-IA Polyimides  

NASA Technical Reports Server (NTRS)

Modified versions of thermoplastic polyimide LaRC(TM)-IA incorporate various amounts of additional, rigid moieties into backbones of LaRC(TM)-IA molecules. Modified versions more resistant to solvents and exhibit higher glass-transition temperatures, yet retain melt-flow processability of unmodified LaRC(TM)-IA.

St. Clair, Terry L.; Chang, Alice C.; Hou, Tan H.; Working, Dennis C.

1994-01-01

247

Magnetic properties of KRE(WO 4) 2 (RE=Gd, Yb, Tm) single crystals  

NASA Astrophysics Data System (ADS)

Magnetic properties of KGd(WO 4) 2, KYb(WO 4) 2 and KTm(WO 4) 2 single crystals have been studied. Temperature and field dependences of the magnetization along the main magnetic axes and angular dependence of the magnetization in the planes settled on the magnetic axes were recorded in the temperature range from 2 up to 100 K and in magnetic field up to 9 T. Paramagnetic Curie temperatures, g-factors and exchange interaction parameters were determined. Different theoretical models were used to describe magnetic properties of KGd(WO 4) 2 and KYb(WO 4) 2 crystals.

Borowiec, M. T.; Zayarnyuk, T.; Pujol, M. C.; Aguiló, M.; Díaz, F.; Zubov, E. E.; Prokhorov, A. D.; Berkowski, M.; Domuchowski, W.; Wisniewski, A.; Puzniak, R.; Pietosa, J.; Dyakonov, V. P.; Baranski, M.; Szymczak, H.

2010-12-01

248

Spectroscopic properties of Yb 3+ in bismuth borate glasses  

Microsoft Academic Search

Absorption spectra, fluorescence spectra and fluorescence decay curves have been measured at room temperature. Spectroscopic and laser performance parameters of Yb3+ in bismuth borate glasses with different compositions and Yb3+ concentrations were calculated. The effects of the host glasses compositions and Yb3+ concentration on the spectroscopic and laser performance parameters have been analyzed. The effect of radiation trapping on the

Yujin Chen; Yidong Huang; Zundu Luo

2003-01-01

249

Comparative performance of passively Q-switched diode-pumped Yb:GGG, Yb:YAG, and Yb-doped tungstates lasers using Cr4+ -doped garnets  

NASA Astrophysics Data System (ADS)

We investigated the CW free-running and repetitive modulation in the kHz frequency domain of a passively Q-switched, diode-pumped Yb:YAG, Yb:GGG and Yb:KYW lasers, by using Cr4+:YAG as a saturable absorber. The results presented here are focused towards the design of a passively Q-switched Yb doped garnets or Yb doped tungstates microlaser. The free-running performance of Yb:YAG, Yb:GGG, Yb:KGW and Yb:KYW were characterized, and experimental parameters such as gain and loss were evaluated. We carried out a fit between our experimental results and an existing numerical model, which relates the experimental and the physical parameters of the ytterbium diode-pumped system to the minimal threshold pumping power. The best performance among the laser crystals was obtained for Yb:YAG laser. A maximum peak power of ?4.5-kW, at an average output power of 1.32-W, were extracted with of ?25 % extraction efficiency.

Kalisky, Y.; Kalisky, O.; Rachum, U.; Boulon, G.; Brenier, A.

2006-03-01

250

Properties of MBE grown CdYbTe and ZnYbTe on GaAs(100) substrates  

NASA Astrophysics Data System (ADS)

ZnYbTe and CdYbTe thin films were grown by molecular beam epitaxy (MBE) on ZnTe and CdTe buffer layers crystallized on GaAs(100) substrates. At the chosen growth temperature (320°C for CdYbTe and 340°C for ZnYbTe) the maximum concentration of ytterbium was found to be 5% in CdTe and 3% in ZnTe. The layers were characterized by X-ray diffraction, photoluminescence (PL) and reflectivity measurements. X-ray investigations have shown that there was a small admixture of pure YbTe in the samples. From the optical measurements it follows that in CdYbTe and ZnYbTe, Yb can be found both in 2 + (as in YbTe) and 3 + (as in Yb doped II-VI compounds) valence state. The relatively broad PL spectra detected at the energies close to the Yb3+4 f13( 2F{5}/{2} ? 2F{7}/{2}) transitions indicate that at such a high concentration Yb incorporates with certain inhomogeneity into the crystal lattices of ZnTe and CdTe.

Sadowski, J.; Dynowska, E.; Szamota-Sadowska, K.; Przedpe?ski, W.; Sitarek, P.; ?witatek, K.

1996-02-01

251

Agricultural applications of TM data  

NASA Technical Reports Server (NTRS)

Multitemporal Thematic Mapper, Thematic Mapper Simulator, and detailed ground truth data were collected for a 9- by 11-km sample segment in Webster County, Iowa, in the summer of 1982. Three dates were acquired each with Thematic Mapper Simulator (June 7, June 23, and July 31) and Thematic Mapper (August 2, September 3, and October 21). The additional TM spectral bands in the middle infrared were found to substantially improve corn/soybean separability in both single date and multitemporal analyses.

Pitts, D. E.; Bizzell, R.; Badhwar, G.; Thompson, D.; Henderson, K.; Shen, S.; Sorensen, C.; Carnes, J.

1984-01-01

252

Rare earth-copper-magnesium compounds RECu{sub 9}Mg{sub 2} (RE=Y, La-Nd, Sm-Ho, Yb) with ordered CeNi{sub 3}-type structure  

SciTech Connect

A series of ternary compounds RECu{sub 9}Mg{sub 2} (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb) have been synthesized via induction melting of elemental metal ingots followed by annealing at 400 deg. C for 4 weeks. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS) was used for examining microstructure and phase composition. These phases crystallize with an ordered version of the binary hexagonal structure type first reported for CeNi{sub 3}. The crystal structure was solved for TbCu{sub 9}Mg{sub 2} from single crystal X-ray counter data (TbCu{sub 9}Mg{sub 2}-structure type, P6{sub 3} /mmc-space group, hP24-Pearson symbol, a=0.49886 (7) nm, c=1.61646 (3) nm, R {sub F}=0.0474 for 190 unique reflections). The Rietveld refinement of the X-ray powder diffraction patterns of RECu{sub 9}Mg{sub 2} confirmed the same crystal structure for the reported rare earth metals. The unit cell volumes for RECu{sub 9}Mg{sub 2} smoothly follow the lanthanide contraction. The existence of a RECu{sub 9}Mg{sub 2} phase was excluded for RE=Er Tm under the investigated experimental conditions. - Graphical abstract: The perspective view of the arrangement of the icosahedrons and anti-cubooctahedrons in the structure of TbCu{sub 9}Mg{sub 2}.

Solokha, P. [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryl and Mefodiy str. 6, 79005 Lviv (Ukraine)]. E-mail: solokha_pavlo@yahoo.com; Pavlyuk, V. [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryl and Mefodiy str. 6, 79005 Lviv (Ukraine); Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland); Saccone, A. [Dipartimento di Chimica e Chimica Industriale, Sezione di Chimica Inorganica e Metallurgia, Universita di Genova, Via Dodecaneso 31, I-16146 Genova (Italy); De Negri, S. [Dipartimento di Chimica e Chimica Industriale, Sezione di Chimica Inorganica e Metallurgia, Universita di Genova, Via Dodecaneso 31, I-16146 Genova (Italy); Prochwicz, W. [Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland); Marciniak, B. [Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland); Rozycka-Sokolowska, E. [Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland)

2006-10-15

253

X-ray absorption study of rare earth ions in Sr 2MgSi 2O 7:Eu 2+,R 3+ persistent luminescence materials  

NASA Astrophysics Data System (ADS)

The valence of the europium dopant and selected rare earth co-dopants (Ce 3+, Dy 3+, and Yb 3+) in the Sr 2MgSi 2O 7:Eu 2+,R 3+ persistent luminescence materials were studied by room temperature XANES measurements. The results indicated the co-existence of both divalent and trivalent europium in all the studied materials. The relative amount of Eu 3+ was observed to increase upon increasing exposure to X-rays, as expected by the persistent luminescence mechanism. This suggests a simultaneous filling of oxygen vacancies initially created by the reducing preparation conditions. For the Dy and Yb co-dopants, only trivalent species were observed. On the other hand, traces of tetravalent cerium were present in the Eu,Ce co-doped materials.

Carlson, Stefan; Hölsä, Jorma; Laamanen, Taneli; Lastusaari, Mika; Malkamäki, Marja; Niittykoski, Janne; Valtonen, Riikka

2009-10-01

254

Optical properties and laser performance of Yb-doped vanadates grown by floating zone method  

NASA Astrophysics Data System (ADS)

We grew high-quality Yb:LuVO4, Yb:GdVO4, and Yb:YVO4 by the floating zone (FZ) method. It was found by measurement that these crystals had favorable optical properties. A maximum absorption coefficient of 27 cm-1 (FWHM) and a fluorescence bandwidth with a 20 nm (FWHM) were observed for Yb:LuVO4 at a Yb doping level of 4 at. %. Finally, we demonstrated the lasing performances of Yb:LuVO4, Yb:GdVO4, and Yb:YVO4. To our knowledge, this is the first time that a Yb-doped vanadate grown by the FZ method has been used as a laser, and 4 at.% Yb doping of the Yb:LuVO4 and Yb:YVO4 is the highest level of doping at which laser oscillation occurs among the Yb-doped vanadates.

Nakamura, Shinki; Agata, Taishi; Ogawa, Takayo; Wada, Satoshi; Higuchi, Mikio

2013-09-01

255

Effects of Second Phase Yb5Sb3 on the Thermoelectric Properties of YbAl3  

NASA Astrophysics Data System (ADS)

The compound YbAl3 exhibits a very high power factor but also rather a large thermal conductivity, leading to a low figure of merit. The second phase Yb5Sb3 was introduced in the YbAl3 matrix to reduce its thermal conductivity. The composites (YbAl3)1- x (Yb5Sb3) x with x = 0, 0.01, 0.05, 0.10, and 0.20 were synthesized by high frequency induction melting, annealing treatment, and spark plasma sintering. The thermoelectric properties of the composites were evaluated. The composites are of n-type conduction. The pure YbAl3 obtained in this work shows a high power factor of 11,500 ?W m-1 K-2 but also a high thermal conductivity of 19.6 W m-1 K-1. However, the existence of Yb5Sb3 compound in the YbAl3 matrix enhances the electrical resistivity and the absolute Seebeck coefficient of the composite, but significantly reduces its thermal conductivity in the temperature range considered, thereby enhancing the figure of merit. The highest ZT value of 0.23 may be obtained in the sample (YbAl3)0.95(Yb5Sb3)0.05 at room temperature, which is apparently higher than that of pure YbAl3.

Li, J. Q.; Liu, X. Y.; Li, Y.; Deng, J. F.; Ye, R. F.; Song, S. H.; Liu, F. S.; Ao, W. Q.

2014-04-01

256

Dual-wavelength ultrashort Yb: fiber amplifier  

NASA Astrophysics Data System (ADS)

Pump-probe spectroscopy of molecular systems requires high average power, short pulse, mid-infrared sources. Today, OPOs can deliver wavelengths of up to 4 µm and THz systems can supply wavelengths beyond 20 µm. To achieve tunable wavelengths in between these two regions, the signal and idler beams of the OPO can be difference frequency mixed again. This two-step nonlinear process necessarily leads to average powers much less than the OPO pump, typically a 1 W Ti:Sapphire laser. The goal of this work is to generate high average power (>1W) pump and signal beams for difference frequency generation at around 15 µm. In this paper, we report initial experimental results of two-wavelength amplification in Yb-doped double cladding fiber (DCF). A novel dual wavelength (1042nm and 1100nm) ultrashort optical pulse Yb fiber amplifier is described. The single stage Yb:fibre amplifier which is pumped by a 965nm diode laser achieved 500 gain yielding 150 mW total power including ASE. The ASE is eliminated with a notch filter. The power in the two colours was increased to 450 mW, with the ASE suppressed in a second Yb fiber amplifier also pumped by a 965nm laser diode.

Liu, Dongfeng; Song, Jie; Strickland, Donna

2004-11-01

257

The Crystal Structure of YB4.  

National Technical Information Service (NTIS)

A structure determination of YB4 was carried out in order to determine the boron positions in metal tetraborides. The structure proposed by earlier workers using the ThB4 was confirmed; however, significant departures in occupany of boron positions were n...

R. F. Giese V. I. Matkovich J. Economy

1965-01-01

258

Spectroscopic properties and quenching mechanisms of Yb3+- doped garnet crystals  

NASA Astrophysics Data System (ADS)

Yb3+ spectroscopic properties are given in garnet crystals. Especially, radiative energy transfer between Yb3+ ions and non-radiative energy transfer between Yb3+ and unexpected rare earth impurities are occurring as quenching mechanisms. Other mechanisms are also suspected from Yb3+ pairs, OH- groups and even traces of Yb2+.

Cañibano, H.; Guyot, Y.; Goutaudier, C.; Laversenne, L.; Boulon, G.

2004-11-01

259

Trapping Yb Atoms for an EDM Experiment  

NASA Astrophysics Data System (ADS)

We are investigating the possible use of a magneto-optical trap (MOT) and optical dipole trap to search for the CP-violating permanent electric dipole moment (EDM) by nuclear spin resonance in Yb (ytterbium) atoms. Optical cooling and trapping of Yb offers many advantages for an atomic EDM experiment including long spin-relaxation lifetimes and a zero average motional magnetic field v×E. The ultra-high vacuum necessary for the trap suppresses spurious magnetic fields due to leakage currents and will allow us to apply a high electric field. Similar EDM experiments have been proposed for the trapped heavy atoms Cs and Fr. However, the ^171Yb atoms are free from the large cross-sections for cold atom collisions that limit the sensitivity of the Cs and Fr experiments because Yb is diamagnetic with a spin-1/2 nucleus. We will use the ^1S0 arrow ^1P1 (398.9 nm) transition for cooling and trapping. The ^1P1 state has a relatively short lifetime of 5 ns, allowing a large laser cooling force to be applied to the atoms. The transition is almost a closed 2-state system, minimizing the need for an extra cleanup laser. We have frequency doubled a Ti:Sapphire laser with an LBO crystal to 398.9 nm and have observed fluorescence from this transition in a Yb beam. We have completed the initial studies for building the MOT and will discuss further progress and possible future experiments. Further information can be found at ?rb"http://www.phys.washington.edu/r~einam/".

Maruyama, Reina; Fortson, Norval; Romalis, Michael

1998-05-01

260

High-power Tm-doped fiber distributed-feedback laser at 1943 nm.  

PubMed

We report on high-power operation of a fiber distributed-feedback (DFB) laser fabricated from Tm-doped photosensitive alumino-silicate fiber and in-band pumped by an Er/Yb fiber laser at 1565 nm. The fiber DFB laser yielded up to 875 mW of single-ended output at 1943 nm on two orthogonally polarized modes for 3.5 W of absorbed pump power. Further scaling of the DFB laser output power was achieved with the aid of a simple Tm-doped fiber amplifier stage spliced directly to the DFB fiber without the need of an optical isolator. The maximum output power from the DFB laser and fiber amplifier was >3 W for a combined absorbed pump power of 8.1 W. The influence of thermal loading, owing to quantum defect heating in the Tm-doped core, on the output power and longitudinal mode behavior is discussed, and the prospects for further improvement in performance are considered. PMID:18794930

Zhang, Z; Shen, D Y; Boyland, A J; Sahu, J K; Clarkson, W A; Ibsen, M

2008-09-15

261

Stereocorrelation of Landsat TM images  

NASA Technical Reports Server (NTRS)

A digital elevation model (DEM) developed from Landsat TM images of a rugged terrain area in north Georgia by automated stereocorrelation techniques yielded an rms error (z), RMSE(z), value of + or - 42 m. Based on the B/H ratio of 0.18 for the Landsat data, this Z-error corresponds to a planimetric correlation accuracy of about + or - 0.3 pixels, confirming that precise correlation can be achieved with operational satellite data. Contours at a 100-m interval interpolated from the DEM show a deviation of + or - 33 m from reference contours obtained from existing 1:24,000-scale maps. The 28.5-m pixel resolution and the weak B/H ratio impose limitations on the accuracy that can be achieved with Landsat TM data. However, it is anticipated that RMSE(z) values of + or - 10 m or less can be achieved with SPOT-1 panchromatic stereo images of 10-m resolution recorded at B/H ratios of 0.5 to 1.0. DEMs generated by stereocorrelation techniques can be used to create orthoimages, perspective views, and topographic map products.

Ehlers, Manfred; Welch, R.

1987-01-01

262

TM waves guided by nonlinear planar waveguides  

Microsoft Academic Search

A numerical method is presented for calculating the dispersion relations and field distributions of stationary nonlinear transverse magnetic (TM) waves guided by optical planar waveguides with intensity-dependent permittivities. The method can treat arbitrary linear permittivity profiles and arbitrary types of the nonlinearity, since it is based on a numerical integration of the nonlinear wave equation. Numerical results for TM waves

Kazuhiko Ogusu

1989-01-01

263

Single crystal growth and various electronic states in Yb-based compounds  

NASA Astrophysics Data System (ADS)

We succeeded in growing single crystals of YbTIn5 (T: Co, Rh, Ir), YbGa4, YbT2Zn20 (T: Co, Rh, Ir), YbPdGe, Yb2Pt2Pb, and YbPd5Al2. The electronic and magnetic properties are clarified by measuring the electrical resistivity, magnetic susceptibility, magnetization, specific heat and de Haas — van Alphen effect.

Hirose, Yusuke; Yoshiuchi, Shingo; Nishimura, Naoto; Sakaguchi, Junya; Enoki, Kentaro; Iwakawa, Ken; Miura, Yasunao; Sugiyama, Kiyohiro; ?nuki, Yoshichika; Settai, Rikio; Takeuchi, Tetsuya; Honda, Fuminori; Matsuda, Tatsuma D.; Ymamoto, Etsuji; Haga, Yoshinori; Hagiwara, Masayuki

2013-06-01

264

Luminescent and scintillation properties of YAG:Tm and YAG:Ce,Tm single crystalline films  

NASA Astrophysics Data System (ADS)

The paper is dedicated to studying the luminescent and scintillation properties of the single crystalline films (SCF) of Tm and Tm-Ce doped Y3Al5O12 garnets grown by the liquid phase epitaxy method. We have found that the effective Tm ? Ce energy transfer is observed in YAG:Ce,Tm SCF. As a result of such transfer, the scintillation light yield of YAG:Ce,Tm SCF under ?-particles excitation can be large in comparison with YAG:Ce SCF counterpart.

Zorenko, Yu.; Gorbenko, V.; Savchyn, V.; Suchocki, A.; Wrzesinski, H.; Walczyk, K.; Fabisiak, K.; Bilski, P.; Twardak, A.

2014-08-01

265

Crystal growth, Yb3+ spectroscopy, concentration quenching analysis and potentiality of laser emission in Ca1-XYbXF2+X  

NASA Astrophysics Data System (ADS)

Ca1-XYbXF2+X crystals were grown by two different methods: simple melting under CF4 atmosphere and the laser heated pedestal growth (LHPG) method under Ar atmosphere. Spectroscopic characterization (absorption, emission, Raman spectroscopy and decay curves) was carried out to identify Stark levels of Yb3+ transitions in the different crystallographic sites of the cubic structure in Ca1-XYbXF2+X crystals. The Yb3+ concentration dependence of the experimental decay time was analysed by using concentration gradient fibre in order to understand involved concentration quenching mechanisms. Under Yb3+ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to unexpected rare earth impurities (Er3+, Tm3+) has been observed in the visible region and interpreted by a limited diffusion process within the Yb3+ doping ion subsystem towards impurities. The main parameters useful for a theoretical approach of laser potentiality have been given as tgrrad = 2.05 ms, N0 = 7.47 × 1021 cm-3 (32 mol%) and Nm = 6.39 × 1021 cm-3 (26.5 mol%).

Ito, Masahiko; Goutaudier, Christelle; Guyot, Yannick; Lebbou, Kheirreddine; Fukuda, Tsuguo; Boulon, Georges

2004-03-01

266

Diode-pumped regenerative Yb:SrF2 amplifier  

NASA Astrophysics Data System (ADS)

We report what we believe to be the first Yb:SrF2 regenerative femtosecond amplifier. The regenerative amplifier produces 325-fs pulses at 100-Hz repetition rate with an energy before compression of 1.4 mJ. The interest of Yb:SrF2 in such regenerative amplifiers and its complementarity to its well-known isotype Yb:CaF2 is also discussed.

Ricaud, S.; Georges, P.; Camy, P.; Doualan, J.-L.; Moncorgé, R.; Courjaud, A.; Mottay, E.; Druon, F.

2012-03-01

267

RbYb(PO3)4  

PubMed Central

Rubidium ytterbium(III) tetra­kis­(polyphosphate), RbYb(PO3)4, was synthesized by solid-state reaction. It adopts structure type IV of the MRE(PO3)4 (M = alkali metal and RE = rare earth metal) family of compounds. The structure is composed of a three-dimensional framework made up from double spiral polyphosphate chains parallel to [10-1] and irregular [YbO8] polyhedra. There are eight PO4 tetra­hedra in the repeat unit of the polyphosphate chains. The Rb+ cation is located in channels extending along [100] that are delimited by the three-dimensional framework. It is surrounded by 11 O atoms, defining an irregular polyhedron.

Zhu, Jing; Chen, Hui

2013-01-01

268

Cryogenic Yb:YAG thin-disk laser  

NASA Astrophysics Data System (ADS)

At cryogenic temperatures, Yb:YAG behaves as a 4-level laser. Its absorption and emission cross-sections increase, and its thermal conductivity improves. Yb:YAG thin disk laser performance at room and cryogenic (80°K) temperatures will be presented. The Yb:YAG gain media is cooled using either a pressurized R134A refrigerant system or by a two-phase liquid nitrogen spray boiler. Interchangeable mounting caps allow the same Yb:YAG media to be switched between the two systems. This allows direct comparison of lasing, amplified spontaneous emission, and temperature performance between 20°C and -200°C.

Vretenar, N.; Carson, T.; Lucas, T.; Newell, T.; Latham, W. P.; Peterson, P.; Bostanci, H.; Lindauer, J. J.; Saarloos, B. A.; Rini, D. P.

2011-10-01

269

Silicidation of Ni(Yb) Film on Si(001)  

NASA Astrophysics Data System (ADS)

The influence of the addition of Yb to Ni on the silicidation of Ni was investigated. The Ni(Yb) film was deposited on a Si(001) substrate by co-sputtering, and silicidation was performed by rapid thermal annealing (RTA). After silicidation, the sheet resistance of the silicide film was measured by the four-point probe method. X-ray diffraction and micro-Raman spectroscopy were employed to identify the silicide phases, and the redistribution of Yb after RTA was characterized by Rutherford backscattering spectrometry and Auger electron spectroscopy. The influence of the Yb addition on the Schottky barrier height (SBH) of the silicide/Si diode was examined by current voltage measurements. The experimental results reveal that the addition of Yb can suppress the formation of the high-resistivity Ni2Si phase, but the formation of low-resistivity NiSi phase is not affected. Furthermore, after silicidation, most of the Yb atoms accumulate in the surface layer and only a small number of Yb atoms pile up at the silicide/Si(001) interface. It is believed that the accumulation of a small amount of Yb at the silicide/Si(001) interface results in the SBH reduction observed in the Ni(Yb)Si/Si diode.

Luo, Jia; Jiang, Yu-Long; Ru, Guo-Ping; Li, Bing-Zong; Chu, Paul K.

2008-03-01

270

Optical spectroscopy of Yb 2+ ions in YbF 3-doped CaF 2 crystals  

Microsoft Academic Search

Transparent colorless Ca1?xYbx F2+x (x=0.0007–0.016) crystals were grown using the vertical Bridgman technique. In order to obtain efficient Yb3+–Yb2+ conversion in the as-grown crystals, a special procedure has been developed. Room temperature optical absorption spectra reveal the characteristic UV absorption bands of the Yb2+ ions in the as-grown crystals, with intensities more than 10 times higher than those reported by

Irina Nicoara; Liliana Lighezan; Monica Enculescu; Ionut Enculescu

2008-01-01

271

Eu{sub 3}F{sub 4}S{sub 2}: Synthesis, crystal structure, and magnetic properties of the mixed-valent europium(II,III) fluoride sulfide EuF{sub 2}.(EuFS){sub 2}  

SciTech Connect

Using the method to synthesize rare-earth metal(III) fluoride sulfides MFS (M=Y, La, Ce-Lu), in some cases we were able to obtain mixed-valent compounds such as Yb{sub 3}F{sub 4}S{sub 2} instead. With Eu{sub 3}F{sub 4}S{sub 2} another isotypic representative has now been synthesized. Eu{sub 3}F{sub 4}S{sub 2} (tetragonal, I4/mmm, a=400.34(2), c=1928.17(9) pm, Z=2) is obtained from the reaction of metallic europium, elemental sulfur, and europium trifluoride in a molar ratio of 5:6:4 within seven days at 850 deg. C in silica-jacketed gas-tightly sealed platinum ampoules. The single-phase product consists of black plate-shaped single crystals with a square cross section, which can be obtained from a flux using equimolar amounts of NaCl as fluxing agent. The crystal structure is best described as an intergrowth structure, in which one layer of CaF{sub 2}-type EuF{sub 2} is followed by two layers of PbFCl-type EuFS when sheeted parallel to the (001) plane. Accordingly there are two chemically and crystallographically different europium cations present. One of them (Eu{sup 2+}) is coordinated by eight fluoride anions in a cubic fashion, the other one (Eu{sup 3+}) exhibits a monocapped square antiprismatic coordination sphere with four F{sup -} and five S{sup 2-} anions. Although the structural ordering of the different charged europium cations is plausible, a certain amount of charge delocalization with some polaron activity has to take place, which is suggested by the black color of the title compound. Temperature dependent magnetic susceptibility measurements of Eu{sub 3}F{sub 4}S{sub 2} show Curie-Weiss behavior with an experimental magnetic moment of 8.19(5) mu{sub B} per formula unit and a paramagnetic Curie temperature of 0.3(2) K. No magnetic ordering is observed down to 4.2 K. In accordance with an ionic formula splitting like (Eu{sup II})(Eu{sup III}){sub 2}F{sub 4}S{sub 2} only one third of the europium centers in Eu{sub 3}F{sub 4}S{sub 2} carry permanent magnetic moments. {sup 151}Eu-Moessbauer spectroscopic experiments at 4.2 K show one signal at an isomer shift of -12.4(1) mm/s and a second one at 0.42(4) mm/s. These signals occur in a ratio of 1:2 and correspond to Eu{sup 2+} and Eu{sup 3+}, respectively. The spectra at 78 and 298 K are similar, thus no change in the Eu{sup 2+}/Eu{sup 3+} fraction can be detected. - Graphical abstract: Crystal structure and {sup 151}Eu-Moessbauer spectra of mixed-valent Eu{sub 3}F{sub 4}S{sub 2}.

Grossholz, Hagen; Hartenbach, Ingo [Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany); Kotzyba, Gunter [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Poettgen, Rainer, E-mail: pottgen@uni-muenster.d [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Trill, Henning; Mosel, Bernd D. [Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Schleid, Thomas, E-mail: schleid@iac.uni-stuttgart.d [Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany)

2009-11-15

272

Magnetic ordering in TmGa.  

PubMed

We have determined the magnetic structure of the intermetallic compound TmGa by high-resolution neutron powder diffraction and (169)Tm Mössbauer spectroscopy. This compound crystallizes in the orthorhombic (Cmcm) CrB-type structure and its magnetic structure is characterized by magnetic order of the Tm sublattice along the a-axis. The initial magnetic ordering occurs at 15(1) K and yields an incommensurate antiferromagnetic structure described by the propagation vector k1 = [0 0.275(2) 0]. At 12 K the dominant ferromagnetic ordering of the Tm sublattice along the a-axis develops in what appears to be a first-order transition. At 3 K the magnetic structure of TmGa is predominantly ferromagnetic but a weakened incommensurate component remains. The ferromagnetic Tm moment reaches 6.7(2) ?B at 3 K and the amplitude of the remaining incommensurate component is 2.7(4) ?B. The (169)Tm hyperfine magnetic field at 5 K is 631(1) T. PMID:24590122

Cadogan, J M; Stewart, G A; Muñoz Pérez, S; Cobas, R; Hansen, B R; Avdeev, M; Hutchison, W D

2014-03-19

273

EU homeland security: citizens or suspects?  

Microsoft Academic Search

EU homeland security agenda and the associated biometric instruments signal the increasing securitisation of the EU but challenge the EU’s commitment to the principles of freedom, democracy and justice. The doctrine of exceptionalism and use of EU biometry to service immigration and internal security priorities (such as combating terrorism and the US homeland security agenda) may compromise EU legitimacy and

JULIET LODGE

2004-01-01

274

Abnormal size-dependent upconversion emissions and multi-color tuning in Er3+-doped CaF2-YbF3 disordered solid-solution nanocrystals  

NASA Astrophysics Data System (ADS)

A series of Er3+-doped (1 - x)CaF2-xYbF3 (0 ? x ? 0.6) disordered solid-solution nanocrystals with various mean sizes were successfully prepared by a facile solvothermal route. Interestingly, abnormal size-dependent upconversion emissions were demonstrated in these nanocrystals for the first time. With increasing grain size, an obvious enhancement of red to green emission ratio was observed in the Er3+ (2 mol%): 0.4CaF2-0.6YbF3 nanocrystals, which is the opposite of the routine size-dependent upconversion emission behavior reported previously. Taking Eu3+ ions as a structural probe, we investigated the influence of a disordered solid-solution structure on Ln3+ luminescence, and proposed that Ln3+ clusters formed in the host should play a key role to induce this unusual size-dependent upconversion emission phenomenon. As a consequence, multi-colors such as green, yellow, and red upconversion emissions can be easily realized by appropriately modifying the Yb3+ content in the Er3+-doped (1 - x)CaF2-xYbF3 nanocrystals. The reported results will deepen the understanding of size effects on the lanthanide upconversion in nanocrystals.

Chen, Daqin; Lei, Lei; Xu, Ju; Yang, Anping; Wang, Yuansheng

2013-03-01

275

Abnormal size-dependent upconversion emissions and multi-color tuning in Er3+-doped CaF2-YbF3 disordered solid-solution nanocrystals.  

PubMed

A series of Er(3+)-doped (1 - x)CaF(2)-xYbF(3) (0 ? x ? 0.6) disordered solid-solution nanocrystals with various mean sizes were successfully prepared by a facile solvothermal route. Interestingly, abnormal size-dependent upconversion emissions were demonstrated in these nanocrystals for the first time. With increasing grain size, an obvious enhancement of red to green emission ratio was observed in the Er(3+) (2 mol%): 0.4CaF(2)-0.6YbF(3) nanocrystals, which is the opposite of the routine size-dependent upconversion emission behavior reported previously. Taking Eu(3+) ions as a structural probe, we investigated the influence of a disordered solid-solution structure on Ln(3+) luminescence, and proposed that Ln(3+) clusters formed in the host should play a key role to induce this unusual size-dependent upconversion emission phenomenon. As a consequence, multi-colors such as green, yellow, and red upconversion emissions can be easily realized by appropriately modifying the Yb(3+) content in the Er(3+)-doped (1 - x)CaF(2)-xYbF(3) nanocrystals. The reported results will deepen the understanding of size effects on the lanthanide upconversion in nanocrystals. PMID:23386131

Chen, Daqin; Lei, Lei; Xu, Ju; Yang, Anping; Wang, Yuansheng

2013-03-01

276

Lumineszenz und sensibilisierte Emission der dreiwertigen Seltenen Erden in Sr 3La 2W 2O 12  

NASA Astrophysics Data System (ADS)

By activation of the new host lattice Sr 3La 2W 2O 12 with the trivalent rare earth ions Nd, Eu, Ho, Er, Tm, Yb an intense emission in the visible and/or infrared region is obtained. Energy transfer from Er 3+ to Tm 3+ and Nd 3+ to Yb 3+ has been found to occur. The excitation, emission, and diffuse reflectance spectra are analyzed for Sr 3La 2W 2O 12: Ln3+ ( Ln = Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb).

Braun, R.; Kemmler-Sack, S.

1984-08-01

277

GdVO4 crystals with Nd3+, Tm3+, Ho3+, and Er3+ ions for diode-pumped microchip laser  

NASA Astrophysics Data System (ADS)

The Nd:GdVO4, Ho:Tm:GdVO4, Tm:GdVO4, Er:GdVO4, Yb:GdVO4 crystals were grown by Czochralski technique. Distribution coefficients of Yb3+, Tm3+, Er3+, Nd3+ ions depend linearly on average radius of a dodecahedral ion. Refractive indices are measured with accuracy within 5 by 10-5 in a range 400 - 1100 nm. Refractive indices depend on the size of the average dodecahedral radius. The thermal conductivity of the doped crystals in the 50 - 300 K temperature range is measured. The thermal conductivity in the <001> crystal direction at a temperature of 300 K is 12.3 W/m by K it is more than thermal conductivity of well-known Nd:YAG laser crystal. As a result of analysis it is shown that vanadate crystals have essential advantages for diode pump lasers in comparison with conventional YAG and YVO4 hosts: large stimulated emission cross section at lasing wavelength; wide absorption band at pump wavelength; low dependency on a pump wavelength and a temperature control of a diode laser; low lasing threshold. For compact design lasers were made crystals with thickness from 2 mm up to 150 micrometers. Microchip laser (monolithic laser) consists of flat-flat cavities formed by a short length of crystal with dielectric cavity mirrors deposited directly on the surfaces.

Zagumennyi, Alexander I.; Zavartsev, Yury D.; Studenikin, Pavel A.; Shcherbakov, Ivan A.; Umyskov, Alexander F.; Popov, Pavel A.; Ufimtsev, Vsevolod B.

1996-03-01

278

Efficient tunable diode-pumped Yb:LYSO laser  

NASA Astrophysics Data System (ADS)

We demonstrated efficient laser action of a new ytterbium-doped oxyorthosilicate crystal Yb:LuYSiO5 (Yb:LYSO) under high-power diode-pumping. The spectroscopic features and laser performance of the alloyed oxyorthosilicate crystal are compared with those of ytterbium-doped lutetium and yttrium oxyorthosilicates. In the continuous-wave laser operation of Yb:LYSO, a maximal slope efficiency of 96% and output power of 7.8 W were respectively achieved with different pump sources. The Yb:LYSO laser exhibits not only little sensitivity to the pump wavelength drift but also a broad tunability. By using a dispersive prism as the intracavity tuning element, we demonstrated that the continuous-wave Yb:LYSO laser exhibit a continuous tunability in the spectral range of 1014-1091 nm.

Li, Wenxue; Xu, Shixiang; Pan, Haifeng; Ding, Liangen; Zeng, Heping; Lu, Wei; Guo, Chunlei; Zhao, Guangjun; Yan, Chengfeng; Su, Liangbi; Xu, Jun

2006-07-01

279

Ternary rare earth-lanthanide sulfides. [Re = Eu, Sm or Yb  

DOEpatents

Disclosed is a new ternary rare earth sulfur compound having the formula La/sub 3-x/M/sub x/S/sub 4/, where M is europium, samarium, or ytterbium, with x = 0.15 to 0.8. The compound has good high-temperature thermoelectric properties and exhibits long-term structural stability up to 1000/sup 0/C.

Takeshita, Takuo; Gschneidner, K.A. Jr.; Beaudry, B.J.

1986-03-06

280

Radiotherapy and Antiangiogenic TM in Lung Cancer  

PubMed Central

Abstract Tetrathiomolybdate (TM) is a potent nontoxic orally delivered copper complexing agent under development for the last several years for the treatment of Wilson's disease. It has been shown to block angiogenesis in primary and metastatic tumors. Therefore, the combination of cytotoxic radiotherapy (RT) and antiangiogenic TM could target both the existing tumor and the tumor microvasculature in a comprehensive strategy. Using a Lewis lung high metastatic (LLHM) carcinoma mouse tumor model, we demonstrate that the combination of TM and RT is more effective than either used as monotherapy. We also show that their therapeutic effects are additive, with no additional toxicity. We show that TM has no significant cytotoxicity in vitro against LLHM tumor cells, further supporting the antiangiogenic mechanism for its action.

Khan, Mohamed K; Miller, Meredith W; Taylor, Jeremy; Gill, Navkiranjit K; Dick, Robert D; Van Golen, Kenneth; Brewer, George J; Merajver, Sofia D

2002-01-01

281

The GEMnet (TM) global data communication  

NASA Technical Reports Server (NTRS)

The GEMnet(TM) (Global Electronics Message network) will provide global digital data communications anywhere in the world at any time for minimum cost. GEMnet(TM) is an end-to-end Non-Voice Non-Geostationary Mobile Satellite (NVNG) (sometimes dubbed 'Little LEO') System which consists of a constellation of 38 low Earth orbiting small satellites and a ground segment. The GEMnet(TM) ground segment will consist of subscriber user terminals, gateway stations, a Network Operational Center(NOC), and a backbone network interconnecting the NOC and gateways. This paper will describe the GEMnet(TM) system concept including ground and space segments, system heritage, data communication services, and protocols.

Yi, Byung K.; Chitty, Richard; Walters, Dave; Howard, Regan

1995-01-01

282

LaRC(TM)-IA Copolyimides  

NASA Technical Reports Server (NTRS)

Copolyimides modified versions of LaRC(TM)-IA thermoplastic polyimide formulated by incorporating moieties of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and, alternatively, isophthaloyldiphthalic anhydride (IDPA) into LaRC(TM)-IA polymer backbones. Exhibit higher glass-transition temperatures and retain greater fractions of lower-temperature shear moduli at higher temperatures. Copolyimides spun into fibers or used as adhesives, molding powders, or matrix resins in many applications, especially in fabrication of strong, lightweight structural components of aircraft.

St. Clair, Terry L.; Chang, Alice C.

1995-01-01

283

Energy transfer properties of Nd3+?Yb3+ in Nd:Yb:LiNbO3 crystals  

NASA Astrophysics Data System (ADS)

Nd:Yb:LiNbO3 nonlinear laser crystal is a candidate for NIR laser around 1000 nm and self-frequency-doubling laser around 500 nm, with mature pump technique using ~808-nm diode laser, via Nd3+ absorption and efficient Nd3+?Yb3+ energy transfer. High-quality Nd:Yb:LiNbO3 crystals were grown by Czochralski method, and the main spectroscopic properties of Nd3+?Yb3+ (Nd3+:4F3/2+Yb3+:2F7/2?Nd3+:4I9/2+Yb3+:2F5/2) energy transfer in LiNbO3 crystals were studied systemically based on emission spectra and luminescence decay curves. Energy transfer efficiency as high as 86% was obtained in a Nd3+ (0.8 mol%) and Yb3+ (2.0 mol%) codoped sample, so Nd:Yb:LiNbO3 laser with a higher efficiency than that of Nd:LiNbO3 laser might be achieved under identical pump conditions.

Sun, Ting; Li, Ai-Hua; Xu, Chao; Xu, Yu-Heng; Wang, Rui

2014-03-01

284

Nanosecond cryogenic Yb:YAG disk laser  

NASA Astrophysics Data System (ADS)

A cryogenic Yb:YAG disk laser is modernised to increase its average and peak power. The master oscillator unit of the laser is considerably modified so that the pulse duration decreases to several nanoseconds with the same pulse energy. A cryogenic disk laser head with a flow-through cooling system is developed. Based on two such laser heads, a new main amplifier is assembled according to an active multipass cell scheme. The total small-signal gain of cryogenic cascades is ~108.

Perevezentsev, E. A.; Mukhin, I. B.; Kuznetsov, I. I.; Vadimova, O. L.; Palashov, O. V.

2014-05-01

285

NIR and CT luminescence spectra of [Yb(TFN)(S-BINAPO)] and [Yb(HFA)(S-BINAPO)] complexes.  

PubMed

The complexes [Yb(TFN)3(S-BINAPO)](TFN=4,4,4-trifluoro-1(2-napthyl)-1,3-butanedione) (complex 1) and [Yb(HFA)3(S-BINAPO)](HFA=hexafluoroacetylacetonate) (complex 2) were synthesized, characterized. The absorption as well as PL spectra have been studied. The complex [Yb(TFN)3(S-BINAPO)] showed narrowed emission peak (half width ?6nm) at around 981nm in addition to several emission peaks in NIR (near infrared) region. The complex [Yb(HFA)3(S-BINAPO)] showed strong emission peak at around 985nm. The charge transfer luminescence of [Yb(TFN)3(S-BINAPO)] was also observed at 412-463nm. PMID:24762571

Subhan, Md Abdus; Nakata, Hiroyasu

2014-09-15

286

Crystal growth and luminescence properties of Yb-doped aluminate, gallate, phosphate and vanadate single crystals  

Microsoft Academic Search

(Lu1?xYbx)3Al5O12 (Yb:LuAG), (Y1?xYbx)AlO3 (Yb:YAP), (Y0.9Yb0.1)VO4 (Yb:YVO) and Ca8(La1.98Yb0.02)(PO4)6O2 (Yb:CLPA) single crystals were grown from the melt. Typical double peak spectrum of the Yb3+ Charge Transfer (CT) luminescence was observed in Yb-doped LuAG and YAP. Strong dependence of decay time and intensity on temperature was observed. Concentration quenching effect in Yb-rich Yb:YAP samples results in pronounced 1\\/e decay time shortening below

A. Yoshikawa; M. Nikl; H. Ogino; J. B. Shim; V. V. Kochurikhin; N. Solovieva; T. Fukuda

2005-01-01

287

Optogalvanic spectroscopy of metastable states in Yb+  

NASA Astrophysics Data System (ADS)

The metastable 2F7/2 and 2D3/2 states of Yb+ are of interest for applications in metrology and quantum information and also act as dark states in laser cooling. These metastable states are commonly repumped to the ground state via the 638.6 nm 2F7/2-1D[5/2]5/2 and 935.2 nm 2D3/2-3D[3/2]1/2 transitions. We have performed optogalvanic spectroscopy of these transitions in Yb+ ions generated in a discharge. We measure the pressure broadening coefficient for the 638.6 nm transition to be 70±10 MHz mbar-1. We place an upper bound of 375 MHz/nucleon on the 638.6 nm isotope splitting and show that our observations are consistent with theory for the hyperfine splitting. Our measurements of the 935.2 nm transition extend those made by Sugiyama et al., showing well-resolved isotope and hyperfine splitting (Sugiyama and Yoda in IEEE Trans. Instrum. Meas. 44: 140, 1995). We obtain high signal-to-noise, sufficient for laser stabilisation applications (Streed et al. in Appl. Phys. Lett. 93: 071103, 2008).

Petrasiunas, M. J.; Streed, E. W.; Weinhold, T. J.; Norton, B. G.; Kielpinski, D.

2012-06-01

288

Eu3+ as a probe for rare-earth dopant site structure in nano-glass-ceramics  

Microsoft Academic Search

Eu3+-doped transparent nano-glass-ceramics, 32(SiO2)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2):3.5(EuF3)mol %, have been prepared aiming at the investigation of the site structure of the Eu3+ rare-earth dopant. In this nano-glass-ceramic host, other rare-earth dopants, such as Er3+, Tm3+, Ho3+, and Dy3+, also have served as a dopant; however the Eu3+ ion is a preferably sensitive probe for a rare-earth dopant site structure due to its unique

K. Driesen; V. K. Tikhomirov; C. Görller-Walrand

2007-01-01

289

Exchange-induced Tm magnetism in multiferroic h-TmMnO3  

NASA Astrophysics Data System (ADS)

Analysis of 169Tm Mössbauer spectra recorded for (hexagonal phase) h- TmMnO3 confirms that the Mn sublattice orders magnetically below TNMn = 82-83 K and reveals the growth of a local Tm moment at the 4b site that is induced by the Mn-Tm exchange interaction. The maximum hyperfine field recorded at the 169Tm nucleus is 312 T, which is just under half of the free ion value and corresponds to a saturation moment of 3.29 µB. The temperature dependence of the fitted magnetic hyperfine interaction is closely represented by a simple two-singlet ground state model for the Tm3+ crystal field scheme. The saturation molecular field is deduced to lie in the range BMn-Tm(T = 0 K) = 1.2-2.3 T, dependent on the expectation value of the coupling ? = lang0|Jz|1rang between the two-singlet states. As observed elsewhere for other hexagonal manganites, there is no Mn-based exchange field at the second Tm site (the 2a site) which contributes a paramagnetic subspectrum down to the lowest experimental temperature of 4.2 K.

Salama, Hazar A.; Stewart, G. A.

2009-09-01

290

Concurrent Validity of LibQUAL+[TM] Scores: What Do LibQUAL+[TM] Scores Measure?  

ERIC Educational Resources Information Center

The present study investigated the validity of LibQUAL+[TM] scores, and specifically how total and subscale LibQUAL+[TM] scores are associated with self-reported, library-related satisfaction and outcomes scores. Participants included 88,664 students and faculty who completed the American English (n[AE] = 69,494) or the British English (n[BE] =…

Thompson, Bruce; Cook, Colleen; Kyrillidou, Martha

2005-01-01

291

TM-align: a protein structure alignment algorithm based on the TM-score.  

PubMed

We have developed TM-align, a new algorithm to identify the best structural alignment between protein pairs that combines the TM-score rotation matrix and Dynamic Programming (DP). The algorithm is approximately 4 times faster than CE and 20 times faster than DALI and SAL. On average, the resulting structure alignments have higher accuracy and coverage than those provided by these most often-used methods. TM-align is applied to an all-against-all structure comparison of 10 515 representative protein chains from the Protein Data Bank (PDB) with a sequence identity cutoff <95%: 1996 distinct folds are found when a TM-score threshold of 0.5 is used. We also use TM-align to match the models predicted by TASSER for solved non-homologous proteins in PDB. For both folded and misfolded models, TM-align can almost always find close structural analogs, with an average root mean square deviation, RMSD, of 3 A and 87% alignment coverage. Nevertheless, there exists a significant correlation between the correctness of the predicted structure and the structural similarity of the model to the other proteins in the PDB. This correlation could be used to assist in model selection in blind protein structure predictions. The TM-align program is freely downloadable at http://bioinformatics.buffalo.edu/TM-align. PMID:15849316

Zhang, Yang; Skolnick, Jeffrey

2005-01-01

292

Modeling Cr-to-Tm and Cr-to-Tm-to-Ho energy transfer in YAG crystals  

NASA Technical Reports Server (NTRS)

A systematic analysis of energy transfer processes in crystals of YAG doped with varying concentrations of Cr and Tm is described. Both spectral measurements and measurements of the temporal response to pulsed excitation are used to give independent determinations of the microscopic interaction parameter for Cr to Tm transfer. The different factors in influencing the temperature dependence of the Cr to Tm transfer are discussed. The dependence of the Tm cross-relaxation rate on Tm concentration is determined.

Swetits, John J.

1991-01-01

293

Physical properties of superbulky lanthanide metallocenes: synthesis and extraordinary luminescence of [Eu(II)(Cp(BIG))2] (Cp(BIG) = (4-nBu-C6H4)5-cyclopentadienyl).  

PubMed

The superbulky deca-aryleuropocene [Eu(Cp(BIG))2], Cp(BIG) = (4-nBu-C6H4)5-cyclopentadienyl, was prepared by reaction of [Eu(dmat)2(thf)2], DMAT = 2-Me2N-?-Me3Si-benzyl, with two equivalents of Cp(BIG)H. Recrystallizyation from cold hexane gave the product with a surprisingly bright and efficient orange emission (45% quantum yield). The crystal structure is isomorphic to those of [M(Cp(BIG))2] (M = Sm, Yb, Ca, Ba) and shows the typical distortions that arise from Cp(BIG)???Cp(BIG) attraction as well as excessively large displacement parameter for the heavy Eu atom (U(eq) = 0.075). In order to gain information on the true oxidation state of the central metal in superbulky metallocenes [M(Cp(BIG))2] (M = Sm, Eu, Yb), several physical analyses have been applied. Temperature-dependent magnetic susceptibility data of [Yb(Cp(BIG))2] show diamagnetism, indicating stable divalent ytterbium. Temperature-dependent (151)Eu Mössbauer effect spectroscopic examination of [Eu(Cp(BIG))2] was examined over the temperature range 93-215?K and the hyperfine and dynamical properties of the Eu(II) species are discussed in detail. The mean square amplitude of vibration of the Eu atom as a function of temperature was determined and compared to the value extracted from the single-crystal X-ray data at 203?K. The large difference in these two values was ascribed to the presence of static disorder and/or the presence of low-frequency torsional and librational modes in [Eu(Cp(BIG))2]. X-ray absorbance near edge spectroscopy (XANES) showed that all three [Ln(Cp(BIG))2] (Ln = Sm, Eu, Yb) compounds are divalent. The XANES white-line spectra are at 8.3, 7.3, and 7.8?eV, for Sm, Eu, and Yb, respectively, lower than the Ln2O3 standards. No XANES temperature dependence was found from room temperature to 100?K. XANES also showed that the [Ln(Cp(BIG))2] complexes had less trivalent impurity than a [EuI2(thf)x] standard. The complex [Eu(Cp(BIG))2] shows already at room temperature strong orange photoluminescence (quantum yield: 45?%): excitation at 412?nm (24,270?cm(-1)) gives a symmetrical single band in the emission spectrum at 606?nm (?max =16495?cm(-1), FWHM: 2090?cm(-1), Stokes-shift: 2140?cm(-1)), which is assigned to a 4f(6)5d(1) ? 4f(7) transition of Eu(II). These remarkable values compare well to those for Eu(II)-doped ionic host lattices and are likely caused by the rigidity of the [Eu(Cp(BIG))2] complex. Sharp emission signals, typical for Eu(III), are not visible. PMID:23907896

Harder, Sjoerd; Naglav, Dominik; Ruspic, Christian; Wickleder, Claudia; Adlung, Matthias; Hermes, Wilfried; Eul, Matthias; Pöttgen, Rainer; Rego, Daniel B; Poineau, Frederic; Czerwinski, Kenneth R; Herber, Rolfe H; Nowik, Israel

2013-09-01

294

Cage Structure Formation of Singly Doped Aluminum Cluster Cations Al n TM + ( TM = Ti, V, Cr)  

NASA Astrophysics Data System (ADS)

Structural information on free transition metal doped aluminum clusters, Al n TM + ( TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size ( n = 5 - 35) and temperature ( T = 145 - 300 K) dependent investigations reveal that bare Al n + clusters are inert toward argon, while Al n TM + clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum cage. The critical size, n crit , is found to be surprisingly large, namely n crit = 16 and n crit = 19 - 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster-argon bond dissociation energies have been derived as function of cluster size from equilibrium mass spectra and are in the 0.1-0.3 eV range.

Lang, Sandra M.; Claes, Pieterjan; Neukermans, Sven; Janssens, Ewald

2011-09-01

295

Molecular geometries, electronic properties, and vibrational spectroscopic studies of endohedral metallofullerenes TM@C 24 and TM@C 24 H 12 (TM = Cr, Mo, and W)  

Microsoft Academic Search

Molecular geometries, electronic properties, and vibrational spectroscopies of TM@C24 and TM@C24H12 (TM = Cr, Mo, and W) in their different spin configurations have been systematically investigated with the hybrid DFT-(U)B3PW91\\u000a functional. The results show that the TM atoms bind over the pentagon ring inside C24 cage, and they move gradually toward the center of C24 cage along with the increasing atomic radii.

Julong Wu; Zhicheng Sun; Xiaojun Li; Liang Chen; Maosheng Tian

2010-01-01

296

A nuclear orientation study of YbVO 4  

Microsoft Academic Search

Nuclear orientation studies on single crystals of tetragonal YbVO4 are reported, using the radioactive isotopes169Yb (I=7\\/2), and175Yb (I=7\\/2). The anisotropies for a number of gamma-rays of both isotopes have been measured at milliKelvin temperatures, in magnetic\\u000a fields up to 0.6T applied along the c-axis. Striking variations of orientation are observed on ramping the magnetic field\\u000a through the anticipated spin inversion

W. D. Hutchison; M. J. Prandolini; D. H. Chaplin; G. J. Bowden; B. Bleaney

1996-01-01

297

The tmRDB and SRPDB resources  

PubMed Central

Maintained at the University of Texas Health Science Center at Tyler, Texas, the tmRNA database (tmRDB) is accessible at the URL with mirror sites located at Auburn University, Auburn, Alabama () and the Royal Veterinary and Agricultural University, Denmark (). The signal recognition particle database (SRPDB) at is mirrored at and the University of Goteborg (). The databases assist in investigations of the tmRNP (a ribonucleoprotein complex which liberates stalled bacterial ribosomes) and the SRP (a particle which recognizes signal sequences and directs secretory proteins to cell membranes). The curated tmRNA and SRP RNA alignments consider base pairs supported by comparative sequence analysis. Also shown are alignments of the tmRNA-associated proteins SmpB, ribosomal protein S1, alanyl-tRNA synthetase and Elongation Factor Tu, as well as the SRP proteins SRP9, SRP14, SRP19, SRP21, SRP54 (Ffh), SRP68, SRP72, cpSRP43, Flhf, SRP receptor (alpha) and SRP receptor (beta). All alignments can be easily examined using a new exploratory browser. The databases provide links to high-resolution structures and serve as depositories for structures obtained by molecular modeling.

Andersen, Ebbe Sloth; Rosenblad, Magnus Alm; Larsen, Niels; Westergaard, Jesper Cairo; Burks, Jody; Wower, Iwona K.; Wower, Jacek; Gorodkin, Jan; Samuelsson, Tore; Zwieb, Christian

2006-01-01

298

Yb\\/Er-codoped and Yb-doped waveguide lasers in phosphate glass  

Microsoft Academic Search

We present experimental and theoretical results of our recent work on the development of waveguide lasers using rare-earth-doped phosphate glasses. An improvement has been achieved over previously reported waveguide laser results using the process of ion exchange in a commercially available Yb\\/Er-codoped phosphate glass composition. We have demonstrated slope efficiencies near 30% with output powers approaching 200 mW for 1540

David L. Veasey; David S. Funk; Philip M. Peters; Norman A. Sanford; Gregory E. Obarski; Norman Fontaine; Matt Young; Adele P. Peskin; Wei-Chih Liu; S. N. Houde-Walter; Joseph S. Hayden

2000-01-01

299

Charge transfer processes and ultraviolet induced absorption in Yb:YAG single crystal laser materials  

NASA Astrophysics Data System (ADS)

Charge transfer (CT) transitions and UV induced color centers in Yb:YAG single crystals have been investigated. A simultaneous pair formation of a stable Yb2+ ion and a hole related (O-) color center (hole polaron) are observed through a CT-process. Slightly different types of hole related color centers are formed in Yb:YAG crystals containing small levels of iron impurities. Furthermore, excitation spectroscopy on the UV irradiated Yb:YAG samples could confirm an energy transfer process between Yb3+ and Yb2+ ions. The findings are important for an increased knowledge of the physical loss mechanisms observed in Yb-doped laser materials, such as the nonlinear decay process in Yb:YAG crystals as well as the photodarkening phenomenon in Yb-doped fiber lasers.

Rydberg, S.; Engholm, M.

2013-06-01

300

Theoretical investigation of CO adsorption on TM-doped (MgO) 12 (TM = Ni, Pd, Pt) nanotubes  

NASA Astrophysics Data System (ADS)

CO adsorption on TM-doped magnesia nanotubes (TM = Ni, Pd and Pt) have been studied by using density functional theory. Our calculation results show that CO favors adsorption on TM-doped magnesia nanotubes in the form of C atom bonding with TM atom. Fukui indices analysis clearly exhibits that doping of impurity TM atom allows for a noticeably enhancement of nucleophilic reactivity ability of magnesia nanotube. The adsorption energies demonstrate that CO molecule is more strongly bound on the 3-fold TM atoms than the 4-fold TM atoms. This finding is well confirmed by TM-C bond length, charge transfer and C-O vibrational frequency. The high adsorption energy of 2.55 eV is found when CO adsorbs on 3-fold Pt in Pt-doped magnesia nanotubes, implying the kind of the doping TM atom has a significant influence on the chemical reactivity.

Yang, Mingxia; Zhang, Yonghong; Huang, Shiping; Liu, Hui; Wang, Peng; Tian, Huiping

2011-12-01

301

Intermediate-valence icosahedral Au-Al-Yb quasicrystal  

NASA Astrophysics Data System (ADS)

A quasiperiodic intermediate-valence (IV) system is realized in an icosahedral Au-Al-Yb quasicrystal. X-ray absorption spectroscopy near the Yb L3 edge indicates that quasiperiodically arranged Yb ions assume a mean valence of 2.61, between a divalent state (4f14, J=0) and a trivalent one (4f13, J=7/2). Magnetization measurements demonstrate that the 4f holes in this quasicrystal have a localized character. The magnetic susceptibility shows a Curie-Weiss behavior above ˜100 K with an effective magnetic moment of 3.81?B per Yb. Moreover, a crystalline approximant to this quasicrystal is an IV compound. We propose a heterogeneous IV model for the quasicrystal, whereas the crystalline approximant is most likely a homogeneous IV system. At temperatures below ˜10 K, specific heat and magnetization measurements reveal non-Fermi-liquid behavior in both the quasicrystal and its crystalline approximant without either doping, pressure, or field tuning.

Watanuki, Tetsu; Kashimoto, Shiro; Kawana, Daichi; Yamazaki, Teruo; Machida, Akihiko; Tanaka, Yukinori; Sato, Taku J.

2012-09-01

302

High power Yb-Raman combined nonlinear fiber amplifier.  

PubMed

We demonstrated a high power Yb-Raman combined nonlinear fiber amplifier. The seed is a 30 W dual-wavelength Yb-doped fiber laser formed by 1070 nm and 1120 nm lasers. The gain medium in the amplifier stage is a 45-meters-long Yb-doped fiber, which power scaled the 1070 nm laser and Raman amplified the 1120 nm laser simultaneously. A record 1120 nm power of 732 W is obtained with pump power of 890 W. Numerical study taking into account of both Yb and Raman gain has been conducted to analyze the output characters and power evolution in the amplifier under different conditions. The numerical results are in good agreement with the experiment. This amplifier is also suitable to amplify laser in the wavelength range of 1100-1150 nm. PMID:24921728

Zhang, Hanwei; Xiao, Hu; Zhou, Pu; Wang, Xiaolin; Xu, Xiaojun

2014-05-01

303

Reactivation of methionine synthase from Thermotoga maritima (TM0268) requires the downstream gene product TM0269.  

PubMed

The crystal structure of the Thermotoga maritima gene product TM0269, determined as part of genome-wide structural coverage of T. maritima by the Joint Center for Structural Genomics, revealed structural homology with the fourth module of the cobalamin-dependent methionine synthase (MetH) from Escherichia coli, despite the lack of significant sequence homology. The gene specifying TM0269 lies in close proximity to another gene, TM0268, which shows sequence homology with the first three modules of E. coli MetH. The fourth module of E. coli MetH is required for reductive remethylation of the cob(II)alamin form of the cofactor and binds the methyl donor for this reactivation, S-adenosylmethionine (AdoMet). Measurements of the rates of methionine formation in the presence and absence of TM0269 and AdoMet demonstrate that both TM0269 and AdoMet are required for reactivation of the inactive cob(II)alamin form of TM0268. These activity measurements confirm the structure-based assignment of the function of the TM0269 gene product. In the presence of TM0269, AdoMet, and reductants, the measured activity of T. maritima MetH is maximal near 80 degrees C, where the specific activity of the purified protein is approximately 15% of that of E. coli methionine synthase (MetH) at 37 degrees C. Comparisons of the structures and sequences of TM0269 and the reactivation domain of E. coli MetH suggest that AdoMet may be bound somewhat differently by the homologous proteins. However, the conformation of a hairpin that is critical for cobalamin binding in E. coli MetH, which constitutes an essential structural element, is retained in the T. maritima reactivation protein despite striking divergence of the sequences. PMID:17656578

Huang, Sha; Romanchuk, Gail; Pattridge, Katherine; Lesley, Scott A; Wilson, Ian A; Matthews, Rowena G; Ludwig, Martha

2007-08-01

304

Reactivation of methionine synthase from Thermotoga maritima (TM0268) requires the downstream gene product TM0269  

PubMed Central

The crystal structure of the Thermotoga maritima gene product TM0269, determined as part of genome-wide structural coverage of T. maritima by the Joint Center for Structural Genomics, revealed structural homology with the fourth module of the cobalamin-dependent methionine synthase (MetH) from Escherichia coli, despite the lack of significant sequence homology. The gene specifying TM0269 lies in close proximity to another gene, TM0268, which shows sequence homology with the first three modules of E. coli MetH. The fourth module of E. coli MetH is required for reductive remethylation of the cob(II)alamin form of the cofactor and binds the methyl donor for this reactivation, S-adenosylmethionine (AdoMet). Measurements of the rates of methionine formation in the presence and absence of TM0269 and AdoMet demonstrate that both TM0269 and AdoMet are required for reactivation of the inactive cob(II)alamin form of TM0268. These activity measurements confirm the structure-based assignment of the function of the TM0269 gene product. In the presence of TM0269, AdoMet, and reductants, the measured activity of T. maritima MetH is maximal near 80°C, where the specific activity of the purified protein is ?15% of that of E. coli methionine synthase (MetH) at 37°C. Comparisons of the structures and sequences of TM0269 and the reactivation domain of E. coli MetH suggest that AdoMet may be bound somewhat differently by the homologous proteins. However, the conformation of a hairpin that is critical for cobalamin binding in E. coli MetH, which constitutes an essential structural element, is retained in the T. maritima reactivation protein despite striking divergence of the sequences.

Huang, Sha; Romanchuk, Gail; Pattridge, Katherine; Lesley, Scott A.; Wilson, Ian A.; Matthews, Rowena G.; Ludwig, Martha

2007-01-01

305

Highly efficient, low-noise Yb femtosecond fiber source  

Microsoft Academic Search

Summary form only given. With the recent availability of Raman-shifted, widely tunable Er fiber laser pulse sources, the direct injection of Yb fiber amplifiers with femtosecond pulses from a frequency-converted Er-fiber laser has become possible. The exploitation of the unique efficiency and large bandwidth of Yb fiber amplifiers thus allows the construction of highly compact ultrafast laser sources operating at

M. E. Fermann; M. L. Stock; A. Galvanauskas; A. Hariharan; G. Sucha; D. Harter; L. Goldberg

2000-01-01

306

[Direct upconversion sensitization luminescence comparison of the ErYb co-doped oxyfluoride fluoride pentaphosphate glass].  

PubMed

This paper investigates the direct upconversion sensitization luminescence of the ErYb co-doped oxyfluoride glass (ErYb: FOG), fluoride glass (ErYb: ZBLAN) and pentaphosphate noncrystalline (ErYb: PP) excited by a 966 nm diode laser. The splendid upconversion luminescence phenomenon is found. It is resulted from that the Yb3+ concentration in rather high, the energy transfer among Er(3+)-Yb3+ and Yb(3+)-Yb3+ ions is rather strong. An important fact is found that the direct upconversion sensitization luminescence of ErYb: FOG is about 100-100,000 times greater than that of ErYb: PP. And meanwhile it is interesting that the upconversion luminescence intensity of ErYb: FOG is near to that of ErYb: ZBLAN. It is significant to enhance the comprehensive level of up-conversion luminescence. PMID:12939953

Chen, Xiao-bo; Chen, Luan; Zhao, Chen-yi; Sawanobori, N; Ma, Hui; Song, Zeng-fu

2003-02-01

307

Beta-Decay Study of ^{150}Er, ^{152}Yb, and ^{156}Yb: Candidates for a Monoenergetic Neutrino Beam Facility  

SciTech Connect

The beta decays of ^{150}Er, ^{152}Yb, and ^{156}Yb nuclei are investigated using the total absorption spectroscopy technique. These nuclei can be considered possible candidates for forming the beam of a monoenergetic neutrino beam facility based on the electron capture (EC) decay of radioactive nuclei. Our measurements confirm that for the cases studied, the EC decay proceeds mainly to a single state in the daughter nucleus.

Estevez Aguado, M. E. [CSIC-Universidad de Valencia; Algora, A. [CSIC-Universidad de Valencia; Rubio, B. [CSIC-Universidad de Valencia; Bernabeu, J. [CSIC-Universidad de Valencia; Nacher, E. [CSIC-Universidad de Valencia; Tain, J. L. [CSIC-Universidad de Valencia; Gadea, A. [CSIC-Universidad de Valencia; Agramunt, J. [CSIC-Universidad de Valencia; Burkard, K. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Hueller, W. [GSI-Hemholtzzentrum fur Schwerionenforschung, Darmstadt, Germany; Doring, J. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Kirchner, R. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Mukha, I. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Plettner, C. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Roeckl, E. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Grawe, H. [GSI-Hemholtzzentrum fur Schwerionenforschung, Darmstadt, Germany; Collatz, R. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Hellstrom, M. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Cano-Ott, D. [CIEMAT, Madrid; Karny, M. [University of Warsaw; Janas, Z. [University of Warsaw; Gierlik, M. [University of Warsaw; Plochocki, A. [University of Warsaw; Rykaczewski, Krzysztof Piotr [ORNL; Batist, L. [Petersburg Nuclear Physics Institute, Gatchina, Russia; Moroz, F. [Petersburg Nuclear Physics Institute, Gatchina, Russia; Wittman, V. [Petersburg Nuclear Physics Institute, Gatchina, Russia; Blazhev, A. [University of Cologne; Valiente, J. J. [INFN, Laboratori Nazionali di Legnaro, Italy; Espinoza, C. [CFPT-IST, Lisbon

2011-01-01

308

Defying Gravity Using Jenga[TM] Blocks  

ERIC Educational Resources Information Center

This paper describes how Jenga[TM] blocks can be used to demonstrate the physics of an overhanging tower that appears to defy gravity. We also propose ideas for how this demonstration can be adapted for the A-level physics curriculum. (Contains 8 figures and 1 table.)

Tan, Yin-Soo; Yap, Kueh-Chin

2007-01-01

309

Doors to Discovery [TM]. WWC Intervention Report  

ERIC Educational Resources Information Center

Doors to Discovery[TM], an early childhood curriculum, focuses on the development of children's vocabulary and expressive and receptive language through a learning process called "shared literacy," where adults and children work together to develop literacy-related skills. Literacy activities, organized into thematic units, encourage children's…

What Works Clearinghouse, 2009

2009-01-01

310

Creation of Yb2O3 Nanoprecipitates Through an Oxidation Process in Bulk Yb-Filled Skutterudites  

NASA Astrophysics Data System (ADS)

An approach to introduce in situ nanoprecipitates into bulk filled skutterudites is developed through controlling the oxidation process of the fillers. Yb0.3Co4Sb12 is selected as the base material, and prolonged oxidation at high temperatures in sealed quartz tubes under a low pressure of oxygen leads to the formation of Yb2O3 nanoinclusions. Transmission electron microscopy shows that the Yb2O3 nanoprecipitates are created within the skutterudite crystal grains through an internal oxidation mechanism. With increased time of oxidation, the amount of Yb2O3 nanoprecipitates is increased and the nanoprecipitates are more uniformly distributed in the matrix. For the samples oxidized for 10 days, the lattice thermal conductivity is reduced by about 19% at 850 K compared with the Yb0.3Co4Sb12 matrix. The reduction in the lattice thermal conductivity originates from additional phonon scattering by the Yb2O3 nanoprecipitates, leading to a maximum ZT of 1.3.

Ding, Juan; Gu, Hui; Qiu, Pengfei; Chen, Xihong; Xiong, Zhen; Zheng, Qiang; Shi, Xun; Chen, Lidong

2013-03-01

311

Relative radiometric calibration of LANDSAT TM reflective bands  

NASA Technical Reports Server (NTRS)

Raw thematic mapper (TM) calibration data from pre-launch tests and in-orbit acquisitions from LANDSAT 4 and 5 satellites are analyzed to assess the radiometric characteristics of the TM sensor. A software program called TM radiometric and algorithmic performance program (TRAPP) was used for the majority of analyses. Radiometric uncertainty in the final TM image originates from: (1) scene variability (solar irradiance and atmospheric scattering); (2) optical and electrical variability of the sensor; and (3) variability introduced during image processing.

Barker, J. L.

1984-01-01

312

Hydrogen in amorphous TM 33 Zr 67 ( TM =Fe, Co, Ni) alloys  

Microsoft Academic Search

Hydrogen sorption properties and some corresponding changes in the crystallization of amorphous TM33Zr67 (TM=Fe, Co, Ni) alloys have been investigated. Relatively large amount of hydrogen was found to dissolve into the amorphous alloys\\u000a during electrochemical hydrogen charging. The microstructural evolution during annealing of H-charged Ni33Zr67 was studied as well. The weaker bonded hydrogen desorbs in a large temperature range (440–625

Tzveta Himitliiska; T. Spassov

2009-01-01

313

Phase diagram for 1/2 Yb2O3-BaO-CuO  

NASA Astrophysics Data System (ADS)

The phase diagram of the 1/2 Yb2O3-BaO-CuO system has been studied in oxygen at 935°C. An inert gas glove box was used for sample manipulation and storage to avoid problems caused by reactions of BaO-rich samples with atmospheric CO2 and H2O. Ternary phases prepared and identified were YbBa2Cu3Ox (Yb-123), YbBa4Cu3Oy (Yb-143), YbBa6Cu3Oz (Yb-163), and Yb2BaCuO5 (Yb-211). Compositions on and around the tie line between Yb-211 and BaCuO2 were also prepared and studied. X-ray diffraction measurements and differential thermal analyses were carried out to identify phases present. Results indicated that the 1/2 Yb2O3-BaO-CuO system is very similar to the 1/2 Y2O3-BaO-CuO system with the same ternary phases and with no extensive solid solution. The Yb-123 phase is the only superconducting phase in the system with an observed Tc of 90+/-1 K. The Yb-163 phase was observed to react rapidly with ambient air.

Peterson, D. E.; Oniyama, E.; Wahlbeck, P. G.; Coulter, J. Y.; Peterson, E. J.

1997-02-01

314

HSP60 interacts with YB-1 and affects its polysome association and subcellular localization  

SciTech Connect

YB-1 is a DNA/RNA-binding protein which, in the cytoplasm, associates with polysomes and regulates translation. However, YB-1 has a novel nuclear localization signal, and its nuclear accumulation is correlated with cancer induction. Here we designated the amino-acid sequence as YB-NLS and demonstrated that YB-NLS is necessary for the nuclear translocation of overexpressed YB-1 in NG108-15 cells. In addition, we found that a heat shock protein, HSP60, binds to YB-NLS in the cytoplasm. Interestingly, when HSP60 expression was repressed, an increase of polysome-associated YB-1 was observed in heavy-sedimenting fractions on a sucrose gradient. Overexpression of HSP60 resulted in a decrease of YB-1 in the heavy-sedimenting fractions and suppression of YB-NLS activity. Furthermore, the NLS-deleted YB-1 was apparently associated with the heavy-sedimenting polysomes. These results suggest that HSP60 interacts with YB-1 at the YB-NLS region and acts as a regulator of polysome association and the subcellular distribution of YB-1.

Ohashi, Sachiyo; Atsumi, Megumi [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)] [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan); Kobayashi, Shunsuke, E-mail: kobayashi.shunsuke@nihon-u.ac.jp [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)] [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)

2009-08-07

315

Sensitization of Pr3+ ions by Eu2+ ions in CaF2 thin films deposited by evaporation  

NASA Astrophysics Data System (ADS)

In the present article, we analyse the possibility of sensitizing the 3Pj levels of Pr3+ ion with Eu2+ ion in CaF2 thin film deposited by evaporation. Indeed, the forbidden nature of the 4f-4f transition of Pr3+ ion makes its absorption too weak for thin film applications, while materials doped with the Pr3+-Yb3+ couple are promising candidates for the achievement of efficient down-converter systems and could allow strong reduction of thermalization losses in silicon solar cells.

Guille, A.; Pereira, A.; Bensalah-Ledoux, A.; Moine, B.; Novotný, M.; Bulí?, J.; Fitl, P.; Lan?ok, J.

2013-11-01

316

Investigation of loss processes of Tm and Tm,Ho in YAG  

NASA Technical Reports Server (NTRS)

The loss of excitation from various manifolds of Tm and Tm,Ho in YAG as a function of temperature and concentration is studied. Two probable loss mechanisms - a Tm up-conversion and a Ho up-conversion - are identified. A 785-nm CW diode laser with 400-nW peak power was focused to a small spot on the sample. The emission from the sample observed at 90 deg was monitored through a monochromator with slits open to 3 mm. Intensity of emission was measured by varying the power of the excitation source using a set of neutral density filters. Power is reported as the percentage of the peak power, and the intensity curves were normalized below 20 percent of transmission. The fact that there is emission above the pump energy indicates an up-conversion from excited manifolds. Nonlinear changes in the intensity of the emission from the Tm 3F4 manifold with the pump power reveals a loss of excitation from this manifold. The linear dependence of the 5I7 manifold emission with pump power at low Tm and high Ho concentrations and the gain of energy in the 5I6 manifold of Ho indicate that the 5I7 manifold loss is due to the coupling of Tm and Ho ions.

Armagan, G.; Buoncristiani, A. M.; Bair, C. H.; Inge, A. T.; Hess, R. V.

1991-01-01

317

Pioneers--The "Engineering byDesign[TM]" Network  

ERIC Educational Resources Information Center

This article discusses the standards-based instruction model, Engineering byDesign[TM] (EbD), and a network of teachers called the Engineering byDesign[TM] Network. Engineering byDesign[TM] is the only standards-based national model for Grades K-12 that delivers technological literacy which was developed by the International Technology Education…

Burke, Barry N.

2006-01-01

318

High-pressure synthesis, crystal structure, and structural relationship of the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}  

SciTech Connect

Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C, representing the first known ytterbium fluoride borate. The compound exhibits isolated BO{sub 3}-groups next to ytterbium cations and fluoride anions, showing a structure closely related to the other known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}. Monoclinic Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} crystallizes in space group C2/c with the lattice parameters a=2028.2(4) pm, b=602.5(2) pm, c=820.4(2) pm, and beta=100.63(3){sup o} (Z=4). Three different ytterbium cations can be identified in the crystal structure, each coordinated by nine fluoride and oxygen anions. None of the five crystallographically independent fluoride ions is coordinated by boron atoms, solely by trigonally-planar arranged ytterbium cations. In close proximity to the above mentioned compounds RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}, Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} can be described via alternating layers with the formal compositions 'YbBO{sub 3}' and 'YbF{sub 3}' in the bc-plane. - Graphical abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}, built up from isolated BO{sub 3}-groups. The compound shows structural relations to the known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}.

Haberer, Almut [Institut fuer Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universitaet Innsbruck, Innrain 52a, A-6020 Innsbruck (Austria); Huppertz, Hubert, E-mail: hubert.huppertz@uibk.ac.a [Institut fuer Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universitaet Innsbruck, Innrain 52a, A-6020 Innsbruck (Austria)

2009-04-15

319

Magnetic transitions and ferromagnetic clusters in RuSr2(Eu,Ce)2Cu2O10+?  

Microsoft Academic Search

The macroscopic magnetizations of a RuSr2(Eu0.7Ce0.3)2Cu2O10+d sample were\\u000ainvestigated. A ferromagnet-like transition occurs around T_M in the low-field\\u000amagnetization. Highly nonlinear M(H), non-Curie-Weiss susceptibility, and slow\\u000aspin-dynamics, however, were observed up to T_1 approx 2-3 T_M. In addition, an\\u000aantiferromagnet-like differential-susceptibility maximum of Ru appears around a\\u000aseparate temperature T_AM between T_1 and T_M. The data are therefore\\u000aconsistent with

Y. Y. Xue; B. Lorenz; D. H. Cao; C. W. Chu

2003-01-01

320

The CSEP EU Testing Center  

NASA Astrophysics Data System (ADS)

The CSEP EU Testing Center at ETH Zurich (eu.cseptesting.org) represents the European node of the Collaboratory for the Study of Earthquake Predictability (CSEP). It is funded in parts through the through the EU project NERIES (www.neries-eu.org/) and serves multiple testing regions within Europe. The first is Italy, sponsored by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). For the Italian testing region, prospective testing of long-term (5 and10 year) models is scheduled to commence April 1 2009. More than 10 models have pre-registered for this testing class. In addition, about 10 short-term models (1 days and 3 months) will be installed at the testing center in Zurich throughout 2009, and added to prospective testing every three months. Models span the full range of purely statistical to mostly physics-based models, and have been contributed from researchers from more than 8 institutions across Europe. Model forecasts are to be evaluated against the earthquakes of magnitude 4 and 5 and above, as reported by INGV. The next testing region that has been proposed is Iceland, with prospective testing possible as early as 2010 if funds become available. In the medium term, testing should become an integral part of the emerging European Plate Observing System (http://www.epos-eu.org/), a research infrastructure for data and observatories on earthquakes, volcanoes, surface dynamics and tectonics. The CSEP EU Testing Center is also gearing up to serve the validation needs of SHARE, the next generation European seismic hazard model, and GEM, the Global Earthquake Model (www.globalquakemodel.org), a private-public partnership with the goal of creating a new global earthquake hazard and risk model by the year 2013. Continuous validation is seen as a critical step for the GEM model to gain acceptance and successively improve the underlying rate models. This presentation will give an update on the status of the testing center and the Italian testing region.

Wiemer, S.; Marzocchi, W.; Schorlemmer, D.; Woessner, J.; Euchner, F.

2009-04-01

321

Nanobulges on surface of silicon film and Si-Yb quantum cascade laser  

NASA Astrophysics Data System (ADS)

Nanosilicon provides pumping levels and the localized states produced from Si-Yb bond on bulge surface of silicon film generate stimulated emission, in which a four-level system is built for chip-laser. The Si-Yb nanobulges on Si film cause a remarkable increase of the surface area and make a buffering layer for mismatch between Si and Yb lattices. Dynamics of photoluminescence and electroluminescence on nanosilicon coated by Yb is investigated. Stimulated peaks near 700 nm are observed on silicon quantum dots coated by Yb. Enhanced EL peaks in the wavelength region from 1300 nm to 1650 nm are measured on the Si film coated by Yb. Si-Yb quantum cascade laser is designed, in which emission wavelength could be manipulated into the window of optical communication by Si-Yb bonding on bulge surface of Si film.

Huang, Wei-Qi; Liu, Shirong; Huang, Zhong-Mei; Miao, Xin-Jian; Qin, Chao-Jian; Lv, Quan

2014-07-01

322

Use of Yb(III) Centered Near Infra-Red (NIR) Luminescence to Determine the Hydration State of a 3,2-HOPO based MRI-Contrast Agent  

SciTech Connect

It has been more than a decade since the first reports of [Gd(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] as a potential new class of magnetic resonance imaging contrast agent (MRI-CA). The defining feature of these 1-methyl-3-hydroxypyridin-2-one (Me-3,2-HOPO) based compounds has been the use of a hexadentate ligand design, and hence an increase in the number of metal bound water molecules, without sacrificing complex stability compared to the typically octadentate contrast agents used commercially. Since that time, significant advances in the properties of these chelates have been steadily reported, including improvements in relaxivity, incorporation into macromolecular architectures and, recently, the first direct verification of solution structure using the discovery of Eu(III) centered luminescence with the isomeric 1-hydroxypyridin-2-one (1,2-HOPO) chelate as a sensitizing chromophore. Nonetheless, it has remained frustrating that direct measurements of the inner sphere hydration state, q, using luminescence techniques with the parent Me-3,2-HOPO compounds have remained elusive, even when direct laser excitation of weakly absorbing f-f transitions were employed (eg. for Eu(III) complexes). This failing can likely be traced to the presence of a low lying LMCT state which efficiently quenches metal based emission. Instead, estimates of the q and hence solution structure have relied on the fitting of relaxivity data to the Solomon-Bloembergen-Morgan equations or, where sufficiently soluble in aqueous solution, studies on the temperature dependence of the paramagnetic contribution to the water {sup 17}O NMR transverse relaxation rate. Recently, Beeby et al reported on a qualitative equation to determine inner sphere hydration based on the change in lifetimes for Yb(III) in going from H{sub 2}O to D{sub 2}O solution, and we reasoned that the lower energy accepting state of Yb(III) may lie below the LMCT state which quenches Eu(III) emission, and hence may facilitate sensitized emission from Yb(III). This hypothesis was borne out experimentally, and herein we describe for the first time sensitized luminescence in the Near Infra-Red (NIR) region from a [Yb(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] complex, and hence the direct measurement of q for the archetypical member of this family of compounds.

Moore, Evan G.; Seitz, Michael; Raymond, Kenneth N.

2008-06-09

323

Gender differences in health of EU10 and EU15 populations: the double burden of EU10 men  

PubMed Central

This study compares gender differences in Healthy Life Years (HLY) and unhealthy life years (ULY) between the original (EU15) and new member states (EU10). Based on the number of deaths, population and prevalence of activity limitations from the Statistics of Living and Income Conditions Survey (SILC) survey, we calculated HLY and ULY for the EU10 and EU15 in 2006 with the Sullivan method. We used decomposition analysis to assess the contributions of mortality and disability and age to gender differences in HLY and ULY. HLY at age 15 for women in the EU10 were 3.1 years more than those for men at the same age, whereas HLY did not differ by gender in the EU15. In both populations ULY at age 15 for women exceeded those for men by 5.5 years. Decomposition showed that EU10 women had more HLY because higher disability in women only partially offset (?0.8 years) the effect of lower mortality (+3.9 years). In the EU15 women’s higher disability prevalence almost completely offset women’s lower mortality. The 5.3 fewer ULY in EU10 men than in EU10 women mainly reflected higher male mortality (4.5 years), while the fewer ULY in EU15 men than in EU15 women reflected both higher male mortality (2.9 years) and higher female disability (2.6 years). The absence of a clear gender gap in HLY in the EU15 thus masked important gender differences in mortality and disability. The similar size of the gender gap in ULY in the EU-10 and EU-15 masked the more unfavourable health situation of EU10 men, in particular the much stronger and younger mortality disadvantage in combination with the virtually absent disability advantage below age 65 in men.

Looman, C. W. N.; Van Oyen, H.; Robine, J. M.; Jagger, C.

2010-01-01

324

Critical behavior of the ferromagnetic perovskites RTiO3 (R = Dy, Ho, Er, Tm, Yb) by magnetocaloric measurements  

NASA Astrophysics Data System (ADS)

Ferromagnetism in perovskites RTiO3 can be induced by a steric effect. The way in which the subtle local structural change can induce three-dimensional (3D) ferromagnetic coupling through Ti-O-Ti superexchange interactions remains controversial. A critical behavior study for the ferromagnetic phase has been made so far only on YTiO3 because the magnetization measurements are plagued by the contribution from the magnetic rare earth. Here we report critical exponents for most ferromagnetic members in the RTiO3 family by measuring the magnetocaloric effect and applying the corresponding scaling laws. Our results indicate that the ferromagnetic coupling in the RTiO3 can be well described by the 3D Heisenberg model.

Su, Yantao; Sui, Yu; Cheng, J.-G.; Zhou, J.-S.; Wang, Xianjie; Wang, Yang; Goodenough, J. B.

2013-05-01

325

Highly efficient cooperative up-conversion of Yb 3+ in NaYF 4  

Microsoft Academic Search

Strong blue cooperative up-conversion emission around 475 nm has been observed in Yb3+-doped hexagonal NaYF4. The influence of concentration of the Yb3+ ion on the luminescence intensity is investigated. It is found that the sample shows the strongest cooperative luminescence\\u000a when the Yb3+ ion concentration is 75%. The investigation shows that hexagonal NaYbF4 is an efficient blue up-converted phosphor, which might

Xiangfu Wang; Siguo Xiao; Xiaoliang Yang; J. W. Ding

2008-01-01

326

JIS YB Lead Complex Perovskite Ferroelectric Material  

NASA Astrophysics Data System (ADS)

Excess WO3 and higher sintering temperature were used for decreasing the temperature dependence of the dielectric constant in Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Mg1/2W1/2)O3 ternary systems. Under some conditions, materials with both JIS YB specifications (dielectric constant change less than 10% over the temperature range from -25 to 85°C) and high dielectric constant, 5000-7400, were obtained. In the materials, core-shell-like distributions of B-site components were observed. These core-shell structures consist of W-rich regions and Ti, Nb-rich regions. In the compositions containing 2% WO3, sintered at 1150°C, core-shell-like domain structures are observed. The fringe pattern corresponded to the Ti, Nb-rich region, and superlattice electron diffraction spots indicating B-site ordering were observed in the W-rich region. In addition, the amounts of WO3 varied the appearance of the core-shell structure.

Uchikoba, Fumio; Sawamura, Kentaro

1992-09-01

327

Determination of the stoichiometry and the Yb 2+ \\/Yb 3+ ratio in YbF x optical IAD films by RBS and in situ XPS analysis  

Microsoft Academic Search

Thin films of YbF3 are interesting as a possible component in antireflection coatings matching the CO2 laser radiation. Ion assisted deposition (IAD) techniques for producing high density films were applied to this material and proved to be most successful in optimising the figures of merit for this purpose (low absorption values, high damage thresholds). Our XPS and RBS measurements, however,

A. Schnellbügel; B. Selle; R. Anton

1997-01-01

328

Phase stability regions in the Na 2CO 3–YbF 3–H 2O system at 190 °C. Crystal structures of two new fluoride carbonates, Na 2Yb(CO 3) 2F and Na 3Yb(CO 3) 2F 2  

Microsoft Academic Search

Phase stability regions in the Na2CO3–YbF3–H2O system at T=190°C, P=11×105 Pa, t=1 h, microwave heating, and the crystal structures of two new carbonate fluorides Na2Yb(CO3)2F and Na3Yb(CO3)2F2 are presented. Five phases, obtained for [YbF3]?0.75 M and [Na]\\/[Yb]<30, are characterized by powder or single crystal X-ray diffraction, thermogravimetric or chemical analyses: NaYb(CO3)F2, Na2Yb(CO3)2F, Na3Yb(CO3)2F2, Na5Yb(CO3)4·2H2O, and Yb(CO3)(OH,F)·xH2O. NaYb(CO3)F2 (a=6.897(7) Å, b=9.118(9) Å,

Amor Ben Ali; Vincent Maisonneuve; Marc Leblanc

2002-01-01

329

TE/TM decomposition of electromagnetic sources  

NASA Technical Reports Server (NTRS)

Three methods are given by which bounded EM sources can be decomposed into two parts radiating transverse electric (TE) and transverse magnetic (TM) fields with respect to a given constant direction in space. The theory applies source equivalence and nonradiating source concepts, which lead to decomposition methods based on a recursive formula or two differential equations for the determination of the TE and TM components of the original source. Decompositions for a dipole in terms of point, line, and plane sources are studied in detail. The planar decomposition is seen to match to an earlier result given by Clemmow (1963). As an application of the point decomposition method, it is demonstrated that the general exact image expression for the Sommerfeld half-space problem, previously derived through heuristic reasoning, can be more straightforwardly obtained through the present decomposition method.

Lindell, Ismo V.

1988-01-01

330

Crystal-field analysis of Eu 3+ energy levels in the new rare-earth R BiY 1- xRxGeO 5 oxide  

NASA Astrophysics Data System (ADS)

Pale colored BiY 1- xRxGeO 5 ( R=rare-earth from Pr to Yb) polycrystalline samples exhibit a crystalline phase isostructural with the orthorhombic Pbca (No. 61) structure-type established for BiYGeO 5 and BiYbGeO 5. R occupies a single point site in the host, with the lowest C1 symmetry. While for Pr and Nd x must be ?0.35, for smaller R ions, Sm to Yb, the phase appears for any x content. Detailed crystallographic data for BiErGeO 5 have been determined from the structure refinement of its neutron diffraction profile at room temperature. Optical absorption and photoluminescence measurements at 10 K have been performed for BiEuGeO 5. An initial approach to the parametrization of crystal-field effects on this new host has been provided by results of the semi-empirical Simple Overlap Model, which considers the crystallographic positions of the nearest neighbors around R. Furthermore, the strongly reduced 7FJM set of levels of the 4 f6 configuration has been taken into account for a trustworthy phenomenological determination of crystal-field parameters of the observed optical center for the Eu 3+ sample. In spite of difficulties imposed by the low symmetry of Eu 3+, a very good root mean squares deviation ?=5.6 cm -1 between experimental and simulated energy level schemes has been obtained considering the approximate C2( Cs) symmetry for the Eu 3+ in the host.

Cascales, C.; Zaldo, C.

2003-02-01

331

An Acidic Protein, YBAP1, Mediates the Release of YB-1 from mRNA and Relieves the Translational Repression Activity of YB-1†  

PubMed Central

Eukaryotic Y-box proteins are nucleic acid-binding proteins implicated in a wide range of gene regulatory mechanisms. They contain the cold shock domain, which is a nucleic acid-binding structure also found in bacterial cold shock proteins. The Y-box protein YB-1 is known to be a core component of messenger ribonucleoprotein particles (mRNPs) in the cytoplasm. Here we disrupted the YB-1 gene in chicken DT40 cells. Through the immunoprecipitation of an epitope-tagged YB-1 protein, which complemented the slow-growth phenotype of YB-1-depleted cells, we isolated YB-1-associated complexes that likely represented general mRNPs in somatic cells. RNase treatment prior to immunoprecipitation led to the identification of a Y-box protein-associated acidic protein (YBAP1). The specific association of YB-1 with YBAP1 resulted in the release of YB-1 from reconstituted YB-1-mRNA complexes, thereby reducing the translational repression caused by YB-1 in the in vitro system. Our data suggest that YBAP1 induces the remodeling of YB-1-mRNA complexes.

Matsumoto, Ken; Tanaka, Kimio J.; Tsujimoto, Masafumi

2005-01-01

332

Low Temperature Phase Transitions in the Heavy Electron Compound YbSb.  

National Technical Information Service (NTIS)

Using Mossbauer spectroscopy on /sup 170/Yb, we detected two low temperature phase transitions in the heavy electron pnictide YbSb. Below T/sub N/= 0.32K antiferromagnetic ordering of Yb/sup 3+/ develops, and between 0.32K and 5K a phase exists whose natu...

P. Bonville J. M. Broto A. Fert

1988-01-01

333

Rare Earth Impurities in YB6 and ZrB12.  

National Technical Information Service (NTIS)

Data is presented on the depression of the superconducting transition temperatures of YB6 and ZrB12 by rare earth impurities. These data show unusual features. Ce in YB6 is in some ways analogous to Yb in ZrB12, and this analogy also appears to hold betwe...

Z. Fisk B. T. Matthias E. Corenzwit

1969-01-01

334

Evolving Bot AI in UnrealTM  

Microsoft Academic Search

\\u000a This paper describes the design, implementation and results of an evolutionary bot inside the PC game UnrealTM, that is, an autonomous enemy which tries to beat the human player and\\/or some other bots. The default artificial intelligence\\u000a (AI) of this bot has been improved using two different evolutionary methods: genetic algorithms (GAs) and genetic programming\\u000a (GP). The first one has

Antonio Miguel Mora; Ramón Montoya; Juan Julián Merelo Guervós; Pablo García-Sánchez; Pedro A. Castillo; Juan Luís Jiménez Laredo; Ana Isabel Martínez García; Anna Espacia

2010-01-01

335

Preliminary evaluation of TM for soils information  

NASA Technical Reports Server (NTRS)

Thematic mapper data acquired over Mississippi County, Arkansas, were examined for utility in separating soil associations within generally level alluvium deposited by the Mississippi River. The 0.76 to 0.90 micron (Band 4) and the 1.55 to 1.75 micron (Band 5) were found to separate the different soil associations fairly well when compared to the USDA-SCS general soil map. The thermal channel also appeared to provide information at this level. A detailed soil survey was available at the field level along with ground observations of crop type, plant height, percent cover and growth stage. Soils within the fields ranged from uniform to soils that occur as patches of sand that stand out strongly against the intermingled areas of dark soil. Examination of the digital values of individual TM bands at the field level indicates that the influence of the soil is greater in TM than it was in MSS bands. The TM appears to provide greater detail of within field variability caused by soils than MSS and thus should provide improved information relating to crop and soil properties. However, this soil influence may cause crop identification classification procedures to have to account for the soil in their algorithms.

Thompson, D. R.; Henderson, K. E.; Houston, A. G.; Pitts, D. E.

1984-01-01

336

Laser spectroscopy of nanocrystalline Eu 2O 3 and Eu 3+:Y 2O 3  

NASA Astrophysics Data System (ADS)

This letter presents optical spectra of Eu 3+ in nanocrystalline Eu 2O 3 and Eu 3+:Y 2O 3. The nanocrystalline particles condense in the monoclinic crystal structure after CO 2-laser vaporization of metal oxide ceramics. The spectra of 14 nm Eu 2O 3 particles have the same sharp lines as do micrometer-size particles, and the spectra of 5 nm Eu 2O 3 particles show the sharp lines superimposed on broad and shifted bands. The spectra of 12 nm particles prepared from Eu 0.2Y 1.8O 3 starting material show two phases that are attributed to slightly disordered Eu 2O 3 and crystalline Eu 3+:Y 2O 3. The spectra of 5 nm particles prepared from Eu 0.2Y 1.8O 3 show broad bands similar to the 5 nm Eu 2O 3 spectra.

Eilers, Hergen; Tissue, Brian M.

1996-03-01

337

Investigation of ?-induced reactions on the p nucleus Yb168  

NASA Astrophysics Data System (ADS)

Cross sections for the Yb168(?,?)Hf172 and Yb168(?,n)Hf171 reactions were measured by means of the activation method using ? particles with energies between 12.9 MeV and 15.1 MeV. The spectroscopy of the ? rays emitted by the reaction products was performed using three different HPGe detector types, namely clover-type high-purity germanium detectors, a low-energy photon spectrometer detector, and a coaxial high-purity germanium detector. The results were compared to Hauser-Feshbach statistical model calculations. Within certain assumptions, astrophysical conclusions could be drawn concerning the production of the p nucleus Yb168. The data in this work can serve as a contribution to the current very fragmentary experimental data base for charged-particle induced reactions. In addition, the absolute intensity for nine ?-ray transitions following the electron capture decay of Hf171 could be derived.

Netterdon, L.; Demetriou, P.; Endres, J.; Giesen, U.; Kiss, G. G.; Sauerwein, A.; Szücs, T.; Zell, K. O.; Zilges, A.

2013-10-01

338

Preparation and characterization of Yb-doped YAG ceramics  

NASA Astrophysics Data System (ADS)

This work presents the results of the preparation of polycrystalline Yb:YAG ceramics for laser sources with dopant concentration from 0 up to 20 at.% via solid state reactive sintering. Samples were prepared via cold isostatic pressing of spray dried mixture of pure oxide powders with TEOS as a sintering aid. Sintering was conducted under high vacuum and clean atmosphere. Various sintering cycles were tested, so that optimum conditions could be selected in dependence on Yb concentration. Samples with optical transmittance higher than 80% were prepared and their laser performance was examined. Slope efficiency as high as 73% and a maximum output power of 6 W were obtained for the sample doped with 10% Yb. Final microstructure of prepared samples was analyzed via optical microscopy, scanning and transmission electron microscopy, and EDS.

Hostaša, Jan; Esposito, Laura; Alderighi, Daniele; Pirri, Angela

2013-02-01

339

Hidden order in Yb2TI2O7  

NASA Astrophysics Data System (ADS)

We report low temperature specific heat and positive muon spin rotation (?-SR) measurements of both polycrystal and single crystal Yb2Ti2O7. Our zero field (ZF) ?-SR shows little spin relaxation temperature dependence in the polycrystal Yb2Ti2O7, contrast to previously reported results. We observe no collinear ferromagnetic order, rather a hidden order ground state where spin fluctuations remain dynamic down to 16 mK. Single crystal Yb2Ti2O7 zero field ?-SR measurements with the crystallographic <111> direction parallel to the initial muon polarization show small but measurable temperature dependence. In addition, our transverse field (TF) ?-SR measurements show the spin susceptibility undergoes a distinct change at temperatures corresponding to the magnetic transition measured in the specific heat.

DÓ Rtenzio, Robert; Dabkowska, Hanna; Dunsiger, Sarah; Goko, Tatsuo; Kycia, Jan; Liu, Lian; Medina, Teresa; Munsie, Timothy; Pomaranski, David; Ross, Kate; Uemura, Yasutomo; Williams, Travis; Luke, Graeme

2013-03-01

340

Yb:YAG Lasers for Space Based Remote Sensing  

NASA Technical Reports Server (NTRS)

Diode pumped solid state lasers will play a prominent role in future remote sensing missions because of their intrinsic high efficiency and low mass. Applications including altimetry, cloud and aerosol measurement, wind velocity measurement by both coherent and incoherent methods, and species measurements, with appropriate frequency converters, all will benefit from a diode pumped primary laser. To date the "gold standard" diode pumped Nd laser has been the laser of choice for most of these concepts. This paper discusses an alternate 1 micron laser, the YB:YAG laser, and its potential relevance for lidar applications. Conceptual design analysis and, to the extent possible at the time of the conference, preliminary experimental data on the performance of a bread board YB:YAG oscillator will be presented. The paper centers on application of YB:YAG for altimetry, but extension to other applications will be discussed.

Ewing, J.J.; Fan, T. Y.

1998-01-01

341

Laser spectroscopy of nanocrystalline Eu 2O 3 and Eu 3+:Y 2O 3  

Microsoft Academic Search

This letter presents optical spectra of Eu3+ in nanocrystalline Eu2O3 and Eu3+:Y2O3. The nanocrystalline particles condense in the monoclinic crystal structure after CO2-laser vaporization of metal oxide ceramics. The spectra of 14 nm Eu2O3 particles have the same sharp lines as do micrometer-size particles, and the spectra of 5 nm Eu2O3 particles show the sharp lines superimposed on broad and

Hergen Eilers; Brian M. Tissue

1996-01-01

342

Valence and environment of rare earth ions in CaAl 2O 4:Eu 2+,R 3+ persistent luminescence materials  

NASA Astrophysics Data System (ADS)

The existence of the different R 2+/R 3+/R IV (R: rare earth) ions as well as the modifications in the structural environment around the dopant and co-dopants in CaAl 2O 4:Eu 2+,R 3+ persistent luminescence materials was studied by L III edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) measurements at Hamburger Synchrotronstrahlungslabor (HASYLAB) at Deutsches Elektronen-Synchrotron (DESY) (Hamburg, Germany). The measurements were carried out at 10 and 296 K for selected rare earth (co-)dopants (Eu 2+; Ce 3+, Nd 3+, Sm 3+, and Yb 3+). The XANES results indicated the co-existence of both divalent and trivalent europium in all co-doped CaAl 2O 4:Eu 2+,R 3+ materials, but only divalent europium in CaAl 2O 4:Eu 2+. The measurement temperature did not affect the XANES results. The interatomic distances extracted from the EXAFS data of the CaAl 2O 4:Eu 2+,R 3+ materials indicated that co-doping creates distortions around the Eu 2+ ions suggesting dopant aggregation.

Hölsä, Jorma; Laamanen, Taneli; Lastusaari, Mika; Malkamäki, Marja; Welter, Edmund; Zajac, Dariusz A.

2010-04-01

343

Magnetic ordering and hybridisation in YbAuCu{4}  

NASA Astrophysics Data System (ADS)

We report on a ^{170}Yb Mössabauer spectroscopy investigation of the low temperature magnetic properties of the cubic heavy electron material YbAuCu4. In the antiferromagnetically ordered phase (T_N=1 K), we measure a 20 % reduction of the Yb^{+3} saturated spontaneous moment with respect to that of the crystal field ?_7 ground state and we evidence a sizeable anisotropy of the interionic magnetic interaction. We interpret these features in terms of 4f electron - conduction electron hybridisation, which accounts for the heavy electron properties. The energy scale k_BT_0 of hybridisation is estimated to be 0.3 K. The Mössbauer spectra in the ordered and paramagnetic phases show inhomogeneous line broadenings which are interpreted as arising from a distribution of local strains along the <~ngle111rangle crystal axes, of mean magneto-elastic energy 0.2 0.4 K. Nous présentons une étude par spectroscopie Mössbauer sur ^{170}Yb des propriétés à basse température du composé cubique à électrons lourds YbAuCu4. Dans la phase antiferromagnétique (T_N=1 K), nous mesurons une réduction de 20 % du moment spontané à saturation de Yb^{+3} par rapport au moment de l'état fondamental ?_7 de champ cristallin, et nous mettons en évidence une anisotropie notable de l'interaction magnétique entre les ions. Nous interprétons ce comportement en termes d'hybridation entre les électrons 4f et les électrons de conduction, qui rend compte des propriétés de type électron lourd. L'échelle d'énergie k_BT_0 de l'hybridation est estimée de l'ordre de 0,3 K. Les spectres Mössbauer dans les phases ordonnée et paramagnétique présentent des élargissements de raie inhomogènes qui sont interprétés en termes de distribution de contraintes locales suivant les axes <111> du cristal, d'énergie magnéto-élastique moyenne 0,2 0,4 K.

Bonville, P.; Canaud, B.; Hammann, J.; Hodges, J. A.; Imbert, P.; Jéhanno, G.; Severing, A.; Fisk, Z.

1992-04-01

344

Magnetism in superconducting EuFe2As1.4P0.6 single crystals studied by local probes  

NASA Astrophysics Data System (ADS)

We have studied the magnetism in superconducting single crystals of EuFe2As1.4P0.6 by using the local probe techniques of zero-field muon spin rotation/relaxation and 151Eu/57Fe Mössbauer spectroscopy. All of these measurements reveal magnetic hyperfine fields below the magnetic ordering temperature TM=18K of the Eu2+ moments. The analysis of the data shows that there is a coexistence of antiferromagnetism, resulting from Eu2+ moments ordered along the crystallographic c-axis, and superconductivity below TSC? 10 K. We find indications for a change in the dynamics of the small Fe magnetic moments (~0.07 ?B) at T*?15K that may be triggering the onset of superconductivity: below T* the Fe magnetic moments seem to be "frozen" within the ab-plane.

Munevar, J.; Micklitz, H.; Alzamora, M.; Argüello, C.; Goko, T.; Ning, F. L.; Munsie, T.; Williams, T. J.; Aczel, A. A.; Luke, G. M.; Chen, G. F.; Yu, W.; Uemura, Y. J.; Baggio-Saitovitch, E.

2014-06-01

345

Is YbAs a heavy Fermion system  

SciTech Connect

Using parameters extracted from a tight binding fit to an ab initio band structure, the specific heat anomaly observed in YbAs around 5 K is computed within the infinite U limit of the degenerate Anderson impurity model. Applying the renormalization procedure derived in variational treatments of the periodic Anderson model, a quasiparticle Fermi surface with strong nesting features and small mass enhancements is obtained. The results suggest that YbAs is not a classical'' heavy Fermion system. 28 refs., 3 figs., 1 tab.

Monnier, R.; Degiorgi, L.; Delley, B.; Koelling, D.D. (Eidgenoessische Technische Hochschule, Zurich (Switzerland). Lab. fuer Festkoerperphysik; Paul Scherrer Inst. (PSI), Villigen (Switzerland); Argonne National Lab., IL (USA))

1989-08-01

346

Electron Paramagnetic Resonance of Yb3+ in Scheelite Single Crystals  

Microsoft Academic Search

The electron paramagnetic resonance spectra of the ground state of trivalent ytterbium have been observed in eight single crystals with scheelite structure at 4.2°K and X band frequencies. The crystals used were CdMoO4, CaWO4, CaMoO4, SrWO4, SrMoO4, PbWO4, PbMoO4, and BaWO4. The tetragonal spectra for Yb171, Yb173, and the even isotopes of ytterbium were best fitted with an axial spin

J. P. Sattler; J. Nemarich

1970-01-01

347

Effect of Yb3+ doping on upconversion emission intensity and mechanism in Er3+/Yb3+-codoped fluorozirconate glasses under 800 nm excitation  

NASA Astrophysics Data System (ADS)

Er3+ singly- and Er3+/Yb3+-codoped fluorozirconate glasses were prepared. The upconversion emission intensities of the Er3+ ion around both 550 and 660 nm were measured under 800 nm excitation. The absorption band of the Yb3+ ion is located around 980 nm. Though the absorption band of Yb3+ does not interact directly with the incident light at 800 nm, both upconversion intensities around 550 and 660 nm emission increased with the increasing YbF3 concentration. We calculated the upconversion intensities around 550 and 660 nm by using rate equations and evaluated the principal upconversion mechanism in Er3+ singly- and Er3+/Yb3+-codoped samples quantitatively. We also investigated the reason for the increase of the upconversion emission intensities with the codoping of Yb3+ under 800 nm excitation.

Tsuda, M.; Soga, K.; Inoue, H.; Inoue, S.; Makishima, A.

1999-12-01

348

Growth and characterization of Yb 3+ doped garnet crystals for scintillator application  

NASA Astrophysics Data System (ADS)

Several concentration of Yb-doped Lu 3Al 5O 12 (Yb:LuAG) and Lu 3Ga 5O 12 (Yb:LGG) single crystals were grown by the micro-pulling-down method. The crystals were seeded-grown in the <1 1 1> direction and transparent and crack free crystals were obtained. Photoluminescence spectra and decay kinetics of these crystals were studied. Charge transfer luminescence of Yb 3+ was observed in both crystals. Mean decay time of about 25 ns at 90 K and strong thermal quenching at room temperature was measured for Yb 5%:LuAG. Radioluminescence intensity was compared to the standard BGO sample.

Ogino, Hiraku; Yoshikawa, Akira; Lee, Jong-Ho; Nikl, Martin; Solovieva, Natalia; Fukuda, Tsuguo

2004-09-01

349

Improvements in the production of Yb:YAG transparent ceramic materials: Spray drying optimisation  

Microsoft Academic Search

Spray drying parameters have been optimized for the preparation of granulated stoichiometric mixture of oxides. These oxides are used in the production of Yb:YAG laser grade ceramic materials by reactive sintering. The selected compositions were Yb0.294Y2.706Al5O12 and Yb0.03Y2.97Al5O12, i.e. YAG doped with 9.8 and 1.0at% of Yb with respect to the overall Y+Yb amount. The influence of solid content, drying

Marina Serantoni; Andreana Piancastelli; Anna Luisa Costa; Laura Esposito

350

Growth and spectral properties of Yb 3+:GdAl 3(BO 3) 4 single crystal  

NASA Astrophysics Data System (ADS)

Ytterbium-doped gadolinium aluminum borate (Yb 3+:GAB) crystal with size up to 25 mm×15 mm×15 mm has been grown by the top seeded solution growth method. The X-ray powder diffraction proved that the structure of the Yb 3+:GAB crystal has the same space group R 32 as pure GAB crystal. The polarized absorption spectra, emission spectra, and fluorescence lifetime of the Yb 3+:GAB crystal were measured at room temperature. The spectroscopic parameters of the crystal were compared with those of Yb 3+:YAl 3(BO 3) 4 crystal. The results showed that the Yb 3+:GAB crystals can also be used as nonlinear laser materials.

Liao, Jinsheng; Lin, Yanfu; Chen, Yujin; Luo, Zundu; Huang, Yidong

2004-09-01

351

Output power improvement in an Yb-doped fiber laser with an additional unpumped Yb-doped fiber  

NASA Astrophysics Data System (ADS)

Master oscillator power amplifier (MOPA) technology has been widely used in high-power or ultrashort-pulse fiber laser systems because the shape of the laser pulse can be easily adjusted. Usually, the first amplification stage of a 1064 nm fiber laser uses the core-pumped Yb-doped fiber amplifier (YDFA); however, the gain or output power is limited owing to the strong amplifier spontaneous emission (ASE) in the 1030 nm band. This paper presents the improved output power in an YDFA by inserting an additional unpumped Yb-doped fiber, which absorbs the lost backward ASE emitted from the pump end. We achieved an output power increase of more than 10% in a low-power signal, and the increase in output power decreased as the signal power increased. Moreover, the insertion of an additional unpumped Yb-doped fiber restricted the unwanted 1030 nm lasing in a low-power signal.

Jeong, Hoon; Park, Hyoyeong; Kim, Seungtaek; Kim, Jongseok; Byun, Chulsoo; Kim, Cheolho

2012-03-01

352

Er/Yb co-doped fiber amplifier with wavelength-tuned Yb-band ring resonator  

NASA Astrophysics Data System (ADS)

Erbium-ytterbium co-doped fiber amplifier with wavelength-tuned Yb-band loop resonator is presented. The amplified spontaneous emission (ASE) from Yb ions is utilized to stimulate a laser emission at several wavelengths from the 1 ?m band in the 1550 nm amplifier. The wavelength of this lasing is tuned by introducing a fiber Bragg grating (FBG). The results show, that the overall efficiency of the amplifier at nominal 1550 nm wavelength can be increased by introducing a feedback loop with 1040 nm and 1050 nm FBG. This loop also protects the Er/Yb amplifier from parasitic lasing at 1 ?m and allows significant output power scaling without risk of self-pulsing.

Sobon, Grzegorz; Sliwinska, Dorota; Kaczmarek, Pawel; Abramski, Krzysztof M.

2012-08-01

353

Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3/Si multilayer deposited on Si substrates  

PubMed Central

Eu2O3/Si multilayer nanostructured films are deposited on Si substrates by magnetron sputtering. Transmission electron microscopy and X-ray diffraction measurements demonstrate that multicrystalline Eu silicate is homogeneously distributed in the film after high-temperature treatment in N2. The Eu2+ silicate is formed by the reaction of Eu2O3 and Si layers, showing an intense and broad room-temperature photoluminescence peak centered at 610 nm. It is found that the Si layer thickness in nanostructures has great influence on Eu ion optical behavior by forming different Eu silicate crystalline phases. These findings open a promising way to prepare efficient Eu2+ materials for photonic application.

2013-01-01

354

Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3/Si multilayer deposited on Si substrates.  

PubMed

Eu2O3/Si multilayer nanostructured films are deposited on Si substrates by magnetron sputtering. Transmission electron microscopy and X-ray diffraction measurements demonstrate that multicrystalline Eu silicate is homogeneously distributed in the film after high-temperature treatment in N2. The Eu2+ silicate is formed by the reaction of Eu2O3 and Si layers, showing an intense and broad room-temperature photoluminescence peak centered at 610 nm. It is found that the Si layer thickness in nanostructures has great influence on Eu ion optical behavior by forming different Eu silicate crystalline phases. These findings open a promising way to prepare efficient Eu2+ materials for photonic application. PMID:23618344

Li, Leliang; Zheng, Jun; Zuo, Yuhua; Cheng, Buwen; Wang, Qiming

2013-01-01

355

Effect of Yb3+ doping on upconversion emission intensity and mechanism in Er3+\\/Yb3+-codoped fluorozirconate glasses under 800 nm excitation  

Microsoft Academic Search

Er3+ singly- and Er3+\\/Yb3+-codoped fluorozirconate glasses were prepared. The upconversion emission intensities of the Er3+ ion around both 550 and 660 nm were measured under 800 nm excitation. The absorption band of the Yb3+ ion is located around 980 nm. Though the absorption band of Yb3+ does not interact directly with the incident light at 800 nm, both upconversion intensities

M. Tsuda; K. Soga; H. Inoue; S. Inoue; A. Makishima

1999-01-01

356

Growth and optical properties of (Yb 3-xY x)Al 5O 12:Ce 3+ single crystals  

NASA Astrophysics Data System (ADS)

To improve the infrared emission of Yb 3+ ions doped in the garnet host Y 3Al 5O 12 (YAG) single crystal through the energy transfer from Ce 3+ to Yb 3+ ions, the <1 1 1>-oriented YAG:Ce 3+, YAG:Yb 3+, YAG:(Ce 3+, Yb 3+) and Yb 3Al 5O 12:Ce 3+ (YbAG:Ce 3+) single crystals were grown using the Czochralski Method, respectively. The excitation and emission spectra of these garnet single crystals were characterized. In YAG:Ce 3+ crystal, the yellow emission of Ce 3+ ions present, but it was completely extinguished in YAG:(Ce 3+, Yb 3+) crystal and YbAG:Ce 3+ crystal. However, the characteristic absorption bands of Ce 3+ still existed in the excitation spectrum of Yb 3+ ions, which showed that the energy absorbed by Ce 3+ ions can be transferred to Yb 3+ ions for its infrared emission.

Zhong, Jiuping; Liu, Chunmeng; Liang, Hongbin; Su, Qiang; Zhou, Jianying; Wang, Jiyang

2011-11-01

357

Dosimetric characterization of a new preparation of BaSO 4 activated by Eu ions  

NASA Astrophysics Data System (ADS)

The results of a thermoluminescent investigation carried out on a new preparation of BaSO 4 activated by Eu ions at different concentrations (0.1, 0.5 and 1.0 mol%) are reported in this paper. Several batches were prepared by varying Dy, Tm and Sm ions concentrations. The TL sensitivity property of each of the doped barium sulphate samples were compared to the BaSO 4:Eu. The highest sensitivity was found for BaSO 4:Eu (0.5 mol%). The main dosimetric characteristics, i.e. thermoluminescent (TL) response as a function of the dose, reproducibility, lower detection limit, and fading, have been investigated for the BaSO 4:Eu. Furthermore, the kinetic parameters, i.e. activation energy, E, the frequency factor, s, the pre-exponential factor s? and the kinetic order, b, have been calculated using initial-rise and deconvolution methods. The peak shape methods related to the geometric properties of a TL peak were also used. In order to analyse the TL response at different energies, the effective atomic number ( Zeff = 45-47) for this material was determined.

González, P. R.; Furetta, C.; Calvo, B. E.; Gaso, M. I.; Cruz-Zaragoza, E.

2007-07-01

358

Magnetic frustration in the disordered pyrochlore Yb(2)GaSbO(7).  

PubMed

In the pyrochlore Yb(2)GaSbO(7), the Yb(3+) sublattice forms a network of corner sharing tetrahedra and the second sublattice is made up of disordered, non-magnetic Ga(3+) and Sb(5+) ions. We have examined this compound using magnetic susceptibility, (170)Yb Mössbauer spectroscopy (down to 0.03 K) and muon spin relaxation (?SR) (down to 0.02 K) measurements. We establish the size of the Yb(3+) magnetic moments and that of the Yb(3+)-Yb(3+) coupling. At low temperatures, the correlated moments fluctuate between directions that are well tilted relative to the local [111] axis. The lattice disorder does not quench the frustration induced low temperature spin fluctuations but it does remove the first order dynamic transition that is present in the crystallographically ordered counterpart Yb(2)Ti(2)O(7). Below 1.0 K, the fluctuation rate of the correlated moments decreases progressively as the temperature is reduced and the moments remain dynamic down to 0.02?K where the rate is 7 × 10(7) s(-1). Magnetic frustration is operative in Yb(2)GaSbO(7) where the Yb(3+)-Yb(3+) interaction is antiferromagnetic as it is in Yb(2)Ti(2)O(7) where the interaction is ferromagnetic. PMID:21471632

Hodges, J A; Dalmas de Réotier, P; Yaouanc, A; Gubbens, P C M; King, P J C; Baines, C

2011-04-27

359

Coexistence of superconductivity and weak ferromagnetism in Eu2-xCexRuSr2Cu2O10-?  

NASA Astrophysics Data System (ADS)

Eu2-xCexRuSr2Cu2O10-?(Ru-2122) is the first Cu-O based system in which superconductivity (SC) in the CuO2 planes and weak-ferromagnetism (W-FM) in the Ru sublattice coexist. The hole doping in the CuO2 planes, is controlled by appropriate variation of the Ce concentration and/or increasing the oxygen concentration. SC occurs for Ce contents of 0.4-0.8, with the highest TC=35 K for Ce=0.6. Due to the granular nature of the materials the magneto-resistance R(H) below TC is positive and unexpected hysteresis loops are observed. The R(H) curve on decreasing the applied field (Hext) is much smaller than the R(H) curve for increasing (Hext). The width of the loops depends strongly on the weak-link properties. The as-prepared non-SC EuCeRuSr2Cu2O10 (x=1) sample exhibits magnetic irreversibility below Tirr=125 K and orders anti-ferromagnetically (AFM) at TM =165 K. Systematic magnetic studies on Eu2-xCexRuSr2Cu2O10-? show that TM, Tirr and Msat decrease with x, and the full Ce dependent magnetic-SC phase diagram is presented. A simple model for the SC state is proposed. The interpretation of the magnetic behavior is: (i) the system becomes antiferromagnetically (AFM) ordered at TM; (b) at Tirr < TM, W-FM is induced by the canting of the Ru moments, and (c), at lower temperatures the appropriate samples become SC at TC. The magnetic features are not affected by the SC state, and the two states coexist.

Felner, Israel

2002-11-01

360

Magnetic and151Eu mössbauer studies on EuTGa (T=Pd AND Pt) compounds  

NASA Astrophysics Data System (ADS)

The compounds EuPdGa and EuPtGa show lattice volume anomaly indicating the abnormal valence state of Eu. in these compounds. Magnetization studies reveal that these compounds are magnetically ordered with a moment of ˜7 ?B/f.u. at 5K. The Curie temperatures obtained from the low field ac susceptibility measurements are 38K for EuPdGa and 36K for EuPtGa.151Eu Mössbauer studies at 300K gave large negative isomer shifts (relative to SmF3) and show a hyperfine split pattern at 4.2K in both the compounds. These results suggest that Eu is in a divalent state in EuPdGa and EuPtGa.

Malik, S. K.; Shenoy, G. K.; Paulose, P. L.; Nagarajan, R.; Dwight, A. E.; Vaishnava, P. P.; Kimball, C. W.

1987-03-01

361

Some dielectric and optical properties of PbF2-codoped CaF2:YbF3 crystals  

Microsoft Academic Search

YbF3-doped and PbF2-codoped CaF2 crystals were grown using the vertical Bridgman method. The optical absorption spectra reveal the existence of both Yb2+ and Yb3+ ions. The Pb2+ ions modify the characteristic absorption peaks of the Yb2+ ions, but do not influence the Yb3+ ion peaks. The dielectric relaxation gives information about the impurity-defect aggregates. The obtained dielectric spectra show that

M. Stef; G. Buse; A. Pruna; I. Nicoara

2009-01-01

362

TE/TM Simulations of Interferometric Measurements  

NASA Technical Reports Server (NTRS)

Interferometric synthetic aperture radar (IFSAR) measurements at X-, C-, L-, and P-band are used to derive ground topography at meter level resolution. Interpretation of the derived topography requires attention due to the complex interaction of the radar signal with ground cover. The presence of penetrable surfaces such as vegetation, and tree canopies poses a challenge since the depth of penetration depends on a number of parameters such as the operating radar frequency, polarization, incident angle, as well as terrain structure. The dependence of the reconstructed topography on polarization may lead to the characterization of the ground cover. Simulation of interferometric measurements is useful for interpretation of the derived topography (B. Houshmand, Proceedings of URSI, 314, 1997). In this talk , time domain simulations for interferometric measurement for TE- and TM- polarization are presented. Time domain simulation includes the effects of the surface material property as well geometry comparable the radar signal wavelength (B. Houshmand, Proceedings of the URSI, 25, 1998). The IFSAR simulation is carried out in two steps. First, the forward scattering data is generated based on full wave analysis. Next, the electromagnetic information is inverted to generate surface topography. This inversion is based on the well known IFSAR processing technique which is composed of signal compression, and formation of an interferogram. The full wave forward scattering data is generated by the scattered-field formulation of the FDTD algorithm. The simulation is carried out by exciting the computational domain by a radar signal. The scattered field is then computed and translated to the receiving interferometric antennas using the time-domain Huygen's principle. The inversion process starts by compressing the time-domain data. The range compressed data from both receivers are then coregistered to form an interferogram. The resulting interferogram is then related to the ground topography using the radar imaging geometry. In this talk, the simulation results are compared with the C-band TM IFSAR derived topography, and the TE/TM SAR images at L-Band.

Houshmand, Bijan

2000-01-01

363

The tmRNA ribosome-rescue system.  

PubMed

The bacterial tmRNA quality control system monitors protein synthesis and recycles stalled translation complexes in a process termed "ribosome rescue." During rescue, tmRNA acts first as a transfer RNA to bind stalled ribosomes, then as a messenger RNA to add the ssrA peptide tag to the C-terminus of the nascent polypeptide chain. The ssrA peptide targets tagged peptides for proteolysis, ensuring rapid degradation of potentially deleterious truncated polypeptides. Ribosome rescue also facilitates turnover of the damaged messages responsible for translational arrest. Thus, tmRNA increases the fidelity of gene expression by promoting the synthesis of full-length proteins. In addition to serving as a global quality control system, tmRNA also plays important roles in bacterial development, pathogenesis, and environmental stress responses. This review focuses on the mechanism of tmRNA-mediated ribosome rescue and the role of tmRNA in bacterial physiology. PMID:22243584

Janssen, Brian D; Hayes, Christopher S

2012-01-01

364

Graphing Calculators, the CBL2[TM] and TI-Interactive[TM] in High School Science.  

ERIC Educational Resources Information Center

This collection of activities is designed to show how TI-Interactive[TM] and Calculator-based Laboratories (CBL) can be used to explore topics in high school science. The activities address such topics as specific heat, Boyle's Law, Newton's Law of Cooling, and Antarctic Ozone Levels. Teaching notes and calculator instructions are included as are…

Molnar, Bill

365

YbNi2: A heavy fermion ferromagnet  

NASA Astrophysics Data System (ADS)

Measurements of the magnetization and specific heat of YbNi2 binary alloy are reported. The DC magnetic susceptibility displays a ferromagnetic behavior with a Curie temperature TC=10.5 K, one of the highest found in Yb compounds. Moreover, the temperature dependence of the specific heat exhibits a lambda anomaly with a peak of 5.12 J/mol K at 9.4 K. The analysis also shows an additional magnetic contribution around 32 K stemming from the crystalline electric field of a quartet at ?1=72 K and a doublet at ?2=126 K, according to the splitting of the Yb3+ ion in cubic symmetry. From the magnetic contribution to the specific heat, a relatively high Kondo temperature TK=27 K is estimated. Below the magnetic transition, the specific heat shows a huge value of the electronic coefficient ?LT=573 mJ/mol K, which is a signature of a heavy fermion behavior. Therefore, this alloy is a fine example of enhanced ferromagnetism and heavy fermion behavior among Yb compounds.

Rojas, D. P.; Fernández Barquín, L.; Echevarria-Bonet, C.; Rodríguez Fernández, J.

2012-10-01

366

Laser and spectroscopic properties of Yb-doped apatite crystals  

NASA Astrophysics Data System (ADS)

Favorable spectroscopic and laser properties were measured in several Yb-doped apatite crystals: Ca5(PO4)(sub 3)F, Sr5(PO4)(sub 3)F, and Ca(5-x)Sr(x)(PO4)(sub 3)F where (x = 1-3). The properties included absorption and emission spectra, and laser pumping (slope efficiency).

Deloach, L. D.; Payne, S. A.; Krupke, W. F.; Smith, L. K.; Kway, W. L.; Tassano, J. B.; Chai, B. H. T.

1993-05-01

367

Multimodal microscopy with sub-30 fs Yb fiber laser oscillator  

PubMed Central

Nonlinear optical microscopy with sub-30 fs pulses from an Yb-fiber laser, approximately three times shorter than typical fiber laser pulses, leads to an order of magnitude brighter third harmonic generation imaging. Multiphoton fluorescence, second and third harmonic generation modalities are compared on stained microspheres and unstained biological tissues.

Nie, Bai; Saytashev, Ilyas; Chong, Andy; Liu, Hui; Arkhipov, Sergey N.; Wise, Frank W.; Dantus, Marcos

2012-01-01

368

Coherent Combining of High-Power Yb Fiber Amplifiers.  

National Technical Information Service (NTIS)

Commercial 0.5-kW Yb-doped fiber amplifiers have been characterized and been found to be suitable for coherent beam combining. Eight such fiber amplifiers have been coherently combined in a tiled-aperture configuration with 78% combining efficiency. The p...

C. X. Yu D. V. Murphy, K. C. Goldizen, S. J. Augst, S. M. Redmond

2011-01-01

369

Gain calculation for Er\\/Yb-doped fiber amplifiers  

Microsoft Academic Search

Gain and output power as a function of pump power has been calculated for short Er\\/Yb doped single mode fibers for various fiber parameters. The calculation shows (i) small signal gain increases with increasing Er concentration, (ii) long fiber lengths provide both higher gain and higher output, (iii) calculated gain is larger for higher Er emission cross section, and, (iv)

Qiang Wang; Robert G. Ahrens; Niloy K. Dutta

2004-01-01

370

High power single-frequency Yb doped fiber amplifiers  

Microsoft Academic Search

We review the recent dramatic advances in high power single-frequency Yb doped fiber amplifiers and discuss fundamental aspects and future prospects. We present up-to-date experimental results with particular attention to cladding-pumped, refined power amplifier regimes.

Y. Jeong; J. Nilsson; D. B. S. Soh; C. A. Codemard; P. Dupriez; C. Farrell; J. K. Sahu; J. Kim; S. Yoo; D. J. Richardson; D. N. Payne

2006-01-01

371

SBS-suppressed, single mode Yb-doped fiber amplifiers  

Microsoft Academic Search

Experimental results are presented demonstrating 100 muJ of pulse energy and over 500 W of peak power from a stimulated Brillouin scattering (SBS)-suppressed, single mode, Yb-doped fiber structure. Over 135 Watts are achieved continuous-wave.

Peter D. Dragic

2009-01-01

372

Unusual Hyperfine Spectra of Yb(3 Plus) IN Scheelites.  

National Technical Information Service (NTIS)

The tetragonal X-band electron paramagnetic resonance spectrum of Yb3+ shows an unusual hyperfine spectrum in the laser host scheelite crystals SrWO4, SrMoO4, PbWO4, and PbMoO4. For these crystals the principal 2I + 1 hyperfine absorption lines of the par...

J. P. Sattler J. Nemarich

1970-01-01

373

Development of the HiLight TM scintillator for computed tomography medical imaging  

NASA Astrophysics Data System (ADS)

The image quality of computed tomography (CT) medical scanners is extremely sensitive to afterglow, radiation damage and optical non-uniformities of scintillators used in X-ray detectors. This represents a tough challenge in the design of scintillator materials with optimum properties. Discussion will center on the development and properties of the first commercialized transparent ceramic scintillator, the (Y,Gd) 2O 3:Eu-based HiLight TM scintillator used in GE Medical System's CT products. The flexibility of the ceramic scintillator platform has enabled it to be engineered to satisfy the changing needs of CT imaging, which is demonstrated by its successful incorporation into over 8000 CT systems worldwide since 1988. The ceramic process makes possible uniform co-doping at ppm levels to control electronic defects responsible for afterglow, reducing it to levels below detectibility in CT images. Annealing of the material in controlled oxygen atmospheres, combined with rapid oxygen diffusion along grain boundaries in the ceramic, reduces radiation damage to negligible values. Transient thermoluminescence of these materials will be discussed as a diagnostic of electronic trap levels responsible for both afterglow and radiation damage. Finally, with the increased scan speed requirements of modern CT systems, energy transfer between the Eu activator and other rare-earth ions can be used to speed the radiative decay of the scintillator, ensuring the material's continued viability in future CT systems.

Duclos, Steven J.; Greskovich, Charles D.; Lyons, Robert J.; Vartuli, James S.; Hoffman, David M.; Riedner, Robert J.; Lynch, Michael J.

2003-06-01

374

Triaxial Superdeformed Bands in ^163Tm  

NASA Astrophysics Data System (ADS)

Following the recent discovery of triaxial superdeformation bands in the Z = 71, 72 nuclei [1,2], we have investigated the Z = 69 nucleus ^163 Tm using the reaction ^130 Te( ^37 Cl, 4n) ^163 Tm with a beam energy of 170 MeV. Gamma-ray spectroscopy was performed using the Gammasphere array at LBNL. The data were sorted into a hypercube. The preliminary results have indicated two bands with ? E _? 60 keV above the previously known 5286 keV, 49/2^- state. These bands appear to talk to one another. It may be recalled that evidence for wobbling motion has recently been reported in the isobaric nucleus ^163 Lu The detailed experimental results and comparisons with the neighboring nuclei will be presented. [1] H. Amro et al, Phys. Lett. B 506, 39(2001). [2] G. Schonwasser eet al., Eur. Phys. J. A13, 291(2002). [3] D. R. Jensen et al, Nucl. Phys. A 703, 3 (2002).

Pattabiraman, N. S.; Ghugre, S. S.; Garg, Umesh; Li, T.; Nayak, B. K.; Zhu, S.; Chakrawarthy, R. S.; Macchiavelli, A. O.; Janssens, R. V. F.

2002-10-01

375

Optical Lattice Clocks Based on Neutral Yb Atoms  

NASA Astrophysics Data System (ADS)

Designer optical lattices are used in a variety of AMO investigations due to their ability to confine atoms under highly controllable conditions. I will describe how we use such lattices (in one or more dimensions) to produce optical atomic clocks that might one day achieve a fractional frequency precision of one part in 10^17 or better. We take advantage of the tight confinement and long interaction times provided by the lattice to perform high resolution spectroscopy on a narrow optical transition in neutral Yb (natural linewidth ˜ 10 mHz) to which we lock the frequency of our clock laser. By tuning the optical lattice to its magic wavelength (at which the induced light shifts are equal for the ground and excited states of the clock reference transition), we remove the effect of the lattice on the clock frequency to first order. To improve further our knowledge of the clock frequency, we evaluate potential shifts due to higher-order lattice effects, background blackbody radiation, and collision effects in over-filled lattices. Through the use of tens of thousands of trapped atoms, we have the potential to achieve high measurement precision in comparatively short averaging times. I will present results for one-dimensional lattice clocks at 578 nm based on two isotopes of Yb. The first uses Yb-171 (nuclear spin, I, =1/2) and has demonstrated an absolute fractional frequency uncertainty below one part in 10^15. The second is based on Yb-174 (I = 0) and uses the technique of magnetic-field induced spectroscopy to excite the atoms. Included will be measurements of the Yb absolute clock frequency at the sub-Hz level, new stability results, and comparisons with other optical clocks. Finally, future directions will be considered including the use of multi-dimensional lattices to isolate the individual atoms.

Oates, Chris

2010-03-01

376

Production and initial structural characterization of the TM4TM5 helix-loop-helix domain of the translocator protein.  

PubMed

Mainly present in the mitochondria, the translocator protein, TSPO, previously known as the peripheral benzodiazepine receptor, is a small essential membrane protein, involved in the translocation of cholesterol across mitochondrial membranes, a rate determining step in steroids biosynthesis. We previously reported the structure of five fragments encompassing the five putative transmembrane helices and showed that each of these fragments constitutes an autonomous folding unit. To further characterize the structural determinants responsible for helix-helix association of this membrane protein, we now investigate the folding of double transmembrane domains in various detergent micelles. Herein, we present the successful biosynthesis of a double transmembrane domain encompassing the last two C-terminal helices (TM4TM5). For optimal production of this domain in Escherichia coli, the evaluation of various peptide constructs, including TM4TM5 fused to different purification tags or to solubilizing proteins, was necessary. The protocol of production of TM4TM5 with more than 95% purity is reported. This domain was further characterized using circular dichroism and solution state NMR. Far-UV circular dichroism studies indicate that the secondary structure of TM4TM5 is highly helical when solubilized in various detergent micelles including n-dodecyl-?-d-maltoside, n-octyl-?-d-glucoside, n-dodecylphosphocholine, 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), and 1-palmitoyl-2-hydroxy-sn-glycero-3-phospho-(1'-rac-glycerol). In addition, the solubilization conditions of the domain were optimized for NMR experiments, and preliminary analysis indicates that TM4TM5 adopts a stable tertiary fold within the TM4TM5-DHPC complex. PMID:23315717

Galvagnion, C; Montaville, P; Coïc, Y-M; Jamin, N

2013-02-01

377

Elevated serum dehydroepiandrosterone sulfate levels in practitioners of the Transcendental Meditation (TM) and TM-Sidhi programs  

Microsoft Academic Search

Serum dehydroepiandosterone sulfate (DHEA-S) levels were measured in 270 men and 153 women who were experienced practitioners of the Transcendental Meditation (TM) and TM-Sidhi programs, mental techniques practiced twice daily, sitting quietly with the eyes closed. These were compared according to sex and 5-year age grouping to 799 male and 453 female nonmeditators. The mean DHEA-S levels in the TM

Jay L. Glaser; Joel L. Brind; Joseph H. Vogelman; Michael J. Eisner; Michael C. Dillbeck; R. Keith Wallace; Deepak Chopra; Norman Orentreich

1992-01-01

378

High magnetic field study of the Tm2Fe17 and Tm2Fe17D3.2 compounds  

NASA Astrophysics Data System (ADS)

A magnetization study of a Tm2Fe17 single crystal and aligned powder of the deuteride Tm2Fe17D3.2 has been carried out in steady (14 T) and pulsed (60 T and, in one case, up to 74 T) magnetic fields at temperatures between 1.5 and 300 K. Tm2Fe17 is a ferrimagnet with TC = 295 K and a spontaneous moment of 22 ?B/f.u. at T = 4.2 K. Of particular interest are low-temperature magnetization curves along the sixfold crystal axis c, which is an easy direction in Tm2Fe17 and a hard direction in the deuteride. In either case the magnetization increases with magnetic field undulatorily in broad steps whose height is a multiple of the atomic moment of Tm, ?Tm = 7 ?B. In Tm2Fe17, the positions of the steps yield information on the Fe-Tm molecular field, 48 T on the Tm 2d site and 60 T on the Tm 2b site, whereas the crystal field parameter A66 is found from the widths of the steps: A66(b) = -35 Ka0-6 and A66(d) = -26 Ka0-6 (here a0 is the Bohr radius). It also proves possible to estimate the other sixth-order crystal field parameter: A60 ˜ -4 Ka0-6 (on average for both sites). Less information can be extracted from the powder data for the deuteride. Thus, the mean molecular field on Tm in Tm2Fe17D3.2 is found to be 49 T or 9% less than in the parent binary compound.

Isnard, O.; Andreev, A. V.; Kuz'min, M. D.; Skourski, Y.; Gorbunov, D. I.; Wosnitza, J.; Kudrevatykh, N. V.; Iwasa, A.; Kondo, A.; Matsuo, A.; Kindo, K.

2013-11-01

379

High-efficiency wavelength and polarization selective grating-waveguide structures for Yb:YAG thin-disk lasers  

NASA Astrophysics Data System (ADS)

We report on Grating Waveguide Structures (GWS) with a high diffraction efficiency used in Littrow configuration to select (and tune) the wavelength of an Yb:YAG thin-disk laser. The structures are composed of a multilayer HR coating, on which an additional low index layer (SiO2) and high index layer (Ta2O5) was deposited. A binary grating with a period of 580 nm is etched on top of the structure with a groove depth of 87 nm for GWS 1 and 72 nm for GWS 2. The simulation results show that the diffraction efficiency in the -1st order can reach a value of 99.99% for TE polarization, whereas it is only about 20% for TM polarization at 1030 nm. The grating was fabricated by standard interference lithography followed by a dry etching process to the desired groove depth. The spectroscopic measurement exhibited a diffraction efficiency of 99.6% for GWS 1 at 1030 nm and 99.7% for GWS 2 at 1048 nm. The devices were placed as end-mirror into the resonator of a Yb:YAG thin-disk laser. An output power of up to 110 W could be obtained from the laser in fundamental-mode operation (M2 ~ 1.2) with GWS 1, corresponding to an optical efficiency of ?oo = 36.2%. In multi-mode operation (M2 ~ 6) a power of 325 W with ?oo = 53.2% could be extracted. The spectral bandwidth of the emitted beam was measured using an Optical Spectrum Analyzer (OSA) to be less than 20 pm in fundamental-mode. We also showed a continuous wavelength tuning range of 46 nm for GWS 1 and of 38 nm for GWS 2. With a commercially available Stokes polarimeter the degree of linear polarization (DOLP) was measured to be higher than 98.6% over the whole power and wavelength tuning range.

Rumpel, Martin; Abdou Ahmed, Marwan; Voss, Andreas; Graf, Thomas

2012-05-01

380

Energy transfer processes and heat generation in Yb3+-doped phosphate glasses  

NASA Astrophysics Data System (ADS)

In this work we present a study of energy transfer processes in Yb3+-doped phosphate glasses with different OH- contents and Yb3+ concentrations. Fluorescence and thermal lens (TL) techniques were used in order to analyze the Yb3+-OH- and Yb3+-other impurity interactions. The role of OH- groups is also presented and discussed. The results show that in the low concentration region up to ~3×1020 Yb ions/cm3, the interaction between Yb3+ and OH radicals is the dominant process reducing the lifetime, increasing the TL dioptric power, and then endangering the performance of the system. For the high Yb3+ concentration limit, the Yb3+-other impurity interaction, which is favored by energy migration, is comparable to the Yb3+-OH- energy transfer, even for high OH- concentration. The nonradiative decay rate due to hydroxyl groups follows Förster-Dexter theory [Ann. Phys. 2, 55 (1948); J. Chem. Phys. 21, 836 (1953)] except at low Yb3+ concentration, being more active at low OH- levels, where quenching rate is probably due to several impurities.

Jacinto, C.; Oliveira, S. L.; Nunes, L. A. O.; Catunda, T.; Bell, M. J. V.

2006-12-01

381

Spectra and energy levels of Yb{sup 3+} in AlN  

SciTech Connect

We report on the crystal-field energy levels calculation of Yb{sup 3+} ions in an AlN host using crystal-field theory. Cathodoluminescence spectra of AlN grown by molecular beam epitaxy on Si (0001) substrate and doped by implantation with ytterbium (Yb) ions were critically examined assuming that Yb{sup 3+} ions are involved in different sites. The comparison between the emission spectra of Yb{sup 3+} ions in the GaN and AlN indicates the presence of some similarities between the lattice locations of Yb{sup 3+} ions in these hosts. We demonstrate that assuming the existence of a substitutional Yb{sub Al(Ga)} site and a V{sub N}-Yb complex defect in AlN (GaN) lattice, a good agreement between the measured and calculated energy values of Yb{sup 3+} ion transition lines can be obtained. Furthermore, we have investigated the Zeeman g{sub ||}) and g{sub perpendicular}) parameters for the Yb{sup 3+} ion in an Al substitutional site as well as in the V{sub N}-Yb complex using the perturbation theory.

Koubaa, T.; Dammak, M.; Kammoun, M. [Departement de Physique, Groupe de Physique Theorique, Laboratoire de Physique Appliquees, Faculte des Sciences de Sfax, Sfax 3018 (Tunisia); Jadwisienczak, W. M.; Lozykowski, H. J. [School of Electrical Engineering and Computer Science, Ohio University, Ohio 4570 (United States); Anders, A. [Plasma Applications Group, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)

2009-07-01

382

LaVo4: Eu Phosphor Films with Enhanced Eu Solubility  

SciTech Connect

Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO{sub 4}:Eu is a promising candidate due to the low Eu-site point symmetry, and thus high dipole transition probability within Judd-Ofelt theory. However, the low solubility limit (< 3 mol %) of Eu in LaVO{sub 4} prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO{sub 4}:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO{sub 4}:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO{sub 4}.

Hwang, Harold

2011-08-11

383

Transport, Thermal, and Magnetic Properties of YbNi3X9 (X = Al, Ga): A Newly Synthesized Yb-Based Kondo Lattice System  

NASA Astrophysics Data System (ADS)

We have succeeded in synthesizing a new Yb-based Kondo lattice system, YbNi3X9 (X = Al, Ga). Our study reveals that YbNi3Al9 shows typical features of a heavy-fermion antiferromagnet with a Néel temperature of TN = 3.4 K. All of the properties reflect a competition between the Kondo effect and the crystalline electric field (CEF) effect. The moderate heavy-fermion state leads to an enhanced Sommerfeld coefficient of 100 mJ/(mol\\cdotK2), even if ordered antiferromagnetically. On the other hand, the isostructural gallide YbNi3Ga9 is an intermediate-valence system with a Kondo temperature of TK = 570 K. A large hybridization scale can overcome the CEF splitting energy, and a moderately heavy Fermi-liquid ground state with high local moment degeneracy should form at low temperatures. Note that the quality of single-crystalline YbNi3X9 is extremely high compared with those of other Yb-based Kondo lattice compounds. We conclude that YbNi3X9 is a suitable system for investigating the electronic structure of Yb-based Kondo lattice systems from a heavy-fermion system with an antiferromagnetically ordered ground state to an intermediate-valence system.

Yamashita, Tetsuro; Miyazaki, Ryoichi; Aoki, Yuji; Ohara, Shigeo

2012-03-01

384

Efficient sensitization of Yb3+ emission by Nd3+ in Y2O3 transparent ceramics and the prospect for high-energy Yb lasers.  

PubMed

Very efficient energy transfer from Nd3+ to Yb3+ in transparent Y2O3 ceramics in the temperature range 10-300 K is demonstrated. It is inferred that this shows potential for the construction of high-energy Yb3+ lasers under diode or flash-lamp excitation of Nd3+. PMID:19823528

Lupei, Voicu; Lupei, Aurelia; Gheorghe, Cristina; Hau, Stefania; Ikesue, Akio

2009-07-15

385

Inside Linden Lab: Second Life [TM] for Educators  

ERIC Educational Resources Information Center

A new culture called Second Life [TM] has emerged that promises innovative strategies for everything from social interactions to business. Some educators believe it may hold new and unique opportunities for teaching and learning. Second Life [TM] (SL) is the creation of Linden Labs, a San Francisco-based corporation defined by its creators as "an…

Atkinson, Tom

2008-01-01

386

Accelerated Math[TM]. What Works Clearinghouse Intervention Report  

ERIC Educational Resources Information Center

"Accelerated Math"[TM], published by Renaissance Learning, is a software tool used to customize assignments and monitor progress in math for students in grades 1-12. The "Accelerated Math"[TM] software creates individualized assignments aligned with state standards and national guidelines, scores student work, and generates reports on student…

What Works Clearinghouse, 2011

2011-01-01

387

Paramagnetic Centers in ZnWO_4:Tm Single Crystals  

NASA Astrophysics Data System (ADS)

Thulium-doped ZnWO4 has been characterized by ESR. Most of the Tm dopant is present as diamagnetic Tm^3+ substituting for Zn^2+; however, a low concentration of Tm^2+ centers with S=1/2 (4f^13 electron configuration) are found by ESR in C1 symmetry. The intensity of this center can be enhanced by a 366-nm UV illumination at 77 K which stimulates an electron transfer to the Tm^3+ ion. The low symmetry is assumed to result from an associated defect, probably an adjacent Zn vacancy, needed for partial charge compensation of the originally built-in Tm^3+ ion; the vacancy remains near the Tm ion even after it captures an electron to become Tm^2+. Furthermore, paramagnetic hole type defects are observed following UV illumination at 77 K. One of these has been characterized by ESR and assigned to an O^- center near a Tm^3+-cation vacancy combination. Supported by the NSF Grant INT-9222297, University of Connecticut Research Foundation, and the Hungarian National Science Research Foundation (OTKA-#7380).

Kappers, L. A.; Gilliam, O. R.; Watterich, A.

1997-03-01

388

Relative radiometric calibration of LANDSAT TM reflective bands  

NASA Technical Reports Server (NTRS)

A common scientific methodology and terminology is outlined for characterizing the radiometry of both TM sensors. The magnitude of the most significant sources of radiometric variability are discussed and methods are recommended for achieving the exceptional potential inherent in the radiometric precision and accuracy of the TM sensors.

Barker, J. L.

1984-01-01

389

Utilising eduroam[TM] Architecture in Building Wireless Community Networks  

ERIC Educational Resources Information Center

Purpose: eduroam[TM] has already been proved to be a scalable, secure and feasible way for universities and research institutions to connect their wireless networks into a WLAN roaming community, but the advantages of eduroam[TM] have not yet been fully discovered in the wireless community networks aimed at regular consumers. This aim of this…

Huhtanen, Karri; Vatiainen, Heikki; Keski-Kasari, Sami; Harju, Jarmo

2008-01-01

390

Electronic structure and f-orbital occupancy in Yb-substituted CeCoIn5  

SciTech Connect

The local structure and 4f orbital occupancy have been investigated in Ce{sub 1?x}Yb{sub x}CoIn{sub 5} via Yb L{sub III}-edge extended x-ray absorption fine structure (EXAFS), Ce and Yb L{sub III}-edge x-ray absorption near-edge structure (XANES), and angle-resolved photoemission spectroscopy (ARPES) measurements. Yb(III) (4f{sup 13}) is the hole analog of Ce(III) (4f{sup 1}). Yb is found to be strongly intermediate-valent in Ce{sub 1?x}Yb{sub x}CoIn{sub 5} throughout the entire doping range, including pure YbCoIn{sub 5}, with an f-hole occupancy for Yb of n{sub f} ? 0.3 (i.e. Yb{sup 2.3+}), independent of Yb concentration and independent of temperature down to T = 20 K. In contrast, the f-electron orbital occupancy for Ce remains close to 1 for all Yb concentrations, suggesting that there is no mutual influence on n{sub f} between neighboring Ce and Yb sites. Likewise, ARPES measurements at 12 K have found that the electronic structure along {Gamma} ? X is not sensitive to the Yb substitution, suggesting that the Kondo hybridization of Ce f electrons with the conduction band is not affected by the presence of Yb impurities in the lattice. The emerging picture is that in Ce{sub 1?x}Yb{sub x}CoIn{sub 5} there are two networks, interlaced but independent, that couple to the conduction band: one network of Ce ions in the heavy-fermion limit, one network of Yb ions in the strongly intermediate-valent limit. The robustness of the local and electronic structure to doping suggests the absence of charge transfer between the Ce and Yb ions, and may explain the relative robustness of superconductivity for this Ce-site substitution as compared to the In-site substitution.

Booth, C. H.; Durakiewicz, T.; Capan, C.; Hurt, D.; Bianchi, A. D.; Joyce, J.J.; Fisk, Z.

2011-05-03

391

Registratiom of TM data to digital elevation models  

NASA Technical Reports Server (NTRS)

Several problems arise when attempting to register LANDSAT thematic mapper data to U.S. B Geological Survey digital elevation models (DEMs). The TM data are currently available only in a rotated variant of the Space Oblique Mercator (SOM) map projection. Geometric transforms are thus; required to access TM data in the geodetic coordinates used by the DEMs. Due to positional errors in the TM data, these transforms require some sort of external control. The spatial resolution of TM data exceeds that of the most commonly DEM data. Oversampling DEM data to TM resolution introduces systematic noise. Common terrain processing algorithms (e.g., close computation) compound this problem by acting as high-pass filters.

1984-01-01

392

Water quality mapping using Landsat TM imagery  

NASA Astrophysics Data System (ADS)

Environmental monitoring through the method of traditional ship sampling is time consuming and requires a high survey cost. The objective of this study is to evaluate the feasibility of Landsat TM imagery for total suspended solids (TSS) mapping using a newly developed algorithm over Penang Island. The study area is the seawater region around Penang Island, Malaysia. Water samples were collected during a 3-hour period simultaneously with the satellite image acquisition and later analyzed in the laboratory above the study area. The samples locations were determined using a handheld GPS. The satellite image was geometrically corrected using the second order polynomial transformation. The satellite image also was atmospheric corrected by using ATCOR2 image processing software. The digital numbers for each band corresponding to the sea-truth locations were extracted and then converted into reflectance values for calibration of the water quality algorithm. The proposed algorithm is based on the reflectance model that is a function of the inherent optical properties of water, which can be related to its constituent's concentrations. The generated algorithm was developed for three visible wavelenghts, red, green and blue for this study. Results indicate that the proposed developed algorithm was superior based on the correlation coefficient (R) and root-mean-square deviation (RMS) values. Finally the proposed algorithm was used for TSS mapping at Penang Island, Malaysia. The generated TSS map was colour-coded for visual interpretation and image smoothing was performed on the map to remove random noise. This preliminary study has produced a promising result. This study indicates that the empirical algorithm is suitable for TSS mapping around Penang Island by using satellite Landsat TM data.

Lim, H. S.; Matjafri, M. Z.; Abdullah, K.; Alias, A. N.; Wong, C. J.; Mustapha-Rosli, M. R.; Mohd Saleh, N.

2009-05-01

393

Structure of Tm2 and Tm2C2 encapsulated in low-symmetry C82(Cs(6)) fullerene cage by single crystal X-ray diffraction  

NASA Astrophysics Data System (ADS)

The molecular structures of Tm2@C82(Cs(6)) and Tm2C2@C82(Cs(6)) are determined by means of single crystal X-ray diffraction using the co-crystals with nickel octaethylporphyrin (Ni(OEP)). The molecular orientations and Tm positions of Tm2@C82(Cs(6)) and Tm2C2@C82(Cs(6)) are basically the same each other. One of the two Tm positions is very close to the Tm position of Tm@C82(Cs(6)). These facts demonstrate that the stable endohedral Tm positions are not fundamentally affected by the addition of the other Tm atoms but dependent on the kind of the fullerene cage structure.

Sado, Yuki; Aoyagi, Shinobu; Izumi, Noriko; Kitaura, Ryo; Kowalczyk, Tim; Wang, Jian; Irle, Stephan; Nishibori, Eiji; Sugimoto, Kunihisa; Shinohara, Hisanori

2014-04-01

394

Crystallization of BaF2-ZnF2-YbF3-ThF4 glass  

NASA Astrophysics Data System (ADS)

The phases and the rates of crystallization in a Ba-Zn-Yb-Th fluoride glass were studied using differential scanning calorimetry, XRD, and observational and chemical SEM analyses. The crystallizing phases that were identified included a BaYbTh fluoride, ZnF2, and YbF3. The BaYbTh fluoride crystallized first at about 450 C, and ZnF2, which was excluded from this phase, crystallized at its surfaces. At higher temperatures, the BaYbTh fluoride phase decomposed partially to BaThF6 and YbF3 phases.

Garcia, Roberto; Doremus, Robert H.; Ko, Sen-Hou; Margraf, Tracey; Bansal, Narottam P.

1988-10-01

395

Synthesis of nano-sized Yb 3Al 5O 12 powders by the urea co-precipitation method  

Microsoft Academic Search

Nano-sized polycrystalline ytterbium aluminum garnet (YbAG, Yb3Al5O12) powders were successfully synthesized by a simple urea co-precipitation method. The thermal behavior of the YbAG precursor was investigated. The calcined amorphous YbAG precursor was directly converted to 20–30nm monophase YbAG at as low as temperature 900°C, without any other intermediate phases. The nano-sized YbAG powders calcined at 900°C distributed evenly with a

Yusong Wu; Jiang Li; Yubai Pan; Qian Liu; Jingkun Guo

2009-01-01

396

Crystallization of BaF2-ZnF2-YbF3-ThF4 glass  

NASA Technical Reports Server (NTRS)

The phases and the rates of crystallization in a Ba-Zn-Yb-Th fluoride glass were studied using differential scanning calorimetry, XRD, and observational and chemical SEM analyses. The crystallizing phases that were identified included a BaYbTh fluoride, ZnF2, and YbF3. The BaYbTh fluoride crystallized first at about 450 C, and ZnF2, which was excluded from this phase, crystallized at its surfaces. At higher temperatures, the BaYbTh fluoride phase decomposed partially to BaThF6 and YbF3 phases.

Garcia, Roberto; Doremus, Robert H.; Ko, Sen-Hou; Margraf, Tracey; Bansal, Narottam P.

1988-01-01

397

Excitation and relaxation of Yb3 + in InPAs and InP  

Microsoft Academic Search

Excitation and relaxation mechanisms of Yb3+ ions in InP and InP0.93As0.07 alloy have been studied based on optically detected cyclotron resonance (ODCR), temperature dependent photoluminescence (PL), and PL decay measurements. It is shown with use of ODCR that charge carriers, most probably electrons, are captured by Yb3+ ions. PL transients show that the decay rate of the Yb3+ PL decreases

M. Godlewski; A. Kozanecki; J. P. Bergman; B. Monemar

1995-01-01

398

Excitation and recombination processes of Yb in InP and InAsP  

Microsoft Academic Search

The excitation and decay mechanisms of the Yb3+ 4f-4f intra-shell emission in InP and InAsP (4% and 7% of As) are analysed. Exciton binding by Yb ion is discussed. The photoluminescence transient measurements indicate that the Yb PL emission is deactivated at increased temperature by energy back-transfer to band states of InP and InAsP.

M. Godlewski; A. Kozanecki; K. Karpi?ska; J. P. Bergman; B. Monemar

1995-01-01

399

Spectroscopic and structural properties of YbF 3-doped fluorophosphate glasses  

Microsoft Academic Search

Compositional influences on the spectroscopic properties of Yb3+ and the structural variations with the introduction of YbF3 were studied in fluorophosphate glasses. Emission cross-section (?emi) and gain coefficient (?emi×?f) were calculated which exhibit maximum at RF2=33mol%. YbF3 has an important effect on the glass forming ability of fluorophosphate glasses when RF2 is over 36mol%. The study of Raman spectra showed

Liyan Zhang; Lei Wen; Junjie Zhang; Lili Hu

2005-01-01

400

Upconversion in Ho 3+ -doped YbF 3 particle prepared by coprecipitation method  

Microsoft Academic Search

YbF3 particles doped with Ho3+ were synthesized by coprecipitation method, from which the ultraviolet and visible emission bands of the Ho3+ and the 480 nm cooperative upconversion emission of Yb3+–Yb3+ are observed under 980 nm excitation. Under the same excitation power, the emission intensity of Ho3+ in coprecipitation method is enhanced by about two times comparing to that in solid-state reaction method.

X. Wang; Y. Bu; S. Xiao; X. Yang; J. W. Ding

2008-01-01

401

Links between the Oncoprotein YB-1 and Small Non-Coding RNAs in Breast Cancer  

PubMed Central

Background The nucleic acid-binding protein YB-1, a member of the cold-shock domain protein family, has been implicated in the progression of breast cancer and is associated with poor patient survival. YB-1 has sequence similarity to LIN28, another cold-shock protein family member, which has a role in the regulation of small noncoding RNAs (sncRNAs) including microRNAs (miRNAs). Therefore, to investigate whether there is an association between YB-1 and sncRNAs in breast cancer, we investigated whether sncRNAs were bound by YB-1 in two breast cancer cell lines (luminal A-like and basal cell-like), and whether the abundance of sncRNAs and mRNAs changed in response to experimental reduction of YB-1 expression. Results RNA-immunoprecipitation with an anti-YB-1 antibody showed that several sncRNAs are bound by YB-1. Some of these were bound by YB-1 in both breast cancer cell lines; others were cell-line specific. The small RNAs bound by YB-1 were derived from various sncRNA families including miRNAs such as let-7 and miR-320, transfer RNAs, ribosomal RNAs and small nucleolar RNAs (snoRNA). Reducing YB-1 expression altered the abundance of a number of transcripts encoding miRNA biogenesis and processing proteins but did not alter the abundance of mature or precursor miRNAs. Conclusions YB-1 binds to specific miRNAs, snoRNAs and tRNA-derived fragments and appears to regulate the expression of miRNA biogenesis and processing machinery. We propose that some of the oncogenic effects of YB-1 in breast cancer may be mediated through its interactions with sncRNAs.

Blenkiron, Cherie; Hurley, Daniel G.; Fitzgerald, Sandra; Print, Cristin G.; Lasham, Annette

2013-01-01

402

High-resolution study of 0{sup +} states in {sup 170}Yb  

SciTech Connect

Recently, 0{sup +} excitations, especially in the rare-earth region, were studied extensively. We extend this work by studying the excited 0{sup +} states in {sup 170}Yb using the {sup 172}Yb(p,t){sup 170}Yb reaction. Eighteen excited 0{sup +} states, 14 of which are new, are observed up to an energy of 3.5 MeV. The results are analyzed using the sd and spdf interacting boson models.

Bettermann, L. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicherstrasse 77, D-50937 Koeln (Germany); Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124 (United States); Heinze, S.; Jolie, J.; Muecher, D.; Moeller, O.; Scholl, C. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicherstrasse 77, D-50937 Koeln (Germany); Casten, R. F. [Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124 (United States); Meyer, D. [Rhodes College, 2000 N. Parkway, Memphis, Tennessee 38112-1690 (United States); Graw, G.; Hertenberger, R.; Wirth, H.-F. [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany); Bucurescu, D. [Horia Hulubei Institute for Physics and Nuclear Engineering, RO-76900 Bucharest (Romania)

2009-10-15

403

The strand separation and nuclease activities associated with YB-1 are dispensable for cisplatin resistance but overexpression of YB-1 in MCF7 and MDA-MB-231 breast tumor cells generates several chemoresistance signatures.  

PubMed

YB-1 is a protein involved in DNA repair, transcription, splicing, translation, and confers cisplatin resistance in several cancers. However, it is unknown which YB-1 activity is required for this resistance. To identify the mechanism(s) by which nuclear YB-1 confers cisplatin resistance, we generated several YB-1 mutants and tested their impact on resistance in the mammary tumor cell lines MCF7 and MDA-MB-231. Transfection of wild type YB-1 bestowed cisplatin resistance in such cells but a mutant YB-1 with a point mutation at position 175 (YB-1(E175A)) did not. A truncated YB-1(1-205) increased cisplatin resistance above the levels conferred by wild type YB-1. The truncated YB-1(1-205) has intact nuclease activities but could not separate a DNA duplex containing a Y-box sequence (activities associated with DNA repair). Moreover, this truncated YB-1(1-205) did not alter splicing of the adenovirus E1A pre-mRNA minigene as it had low binding affinity for several splicing factors. In contrast, the mutant YB-1(E175A) protein behaved like wild type YB-1 regarding all these activities but yet did not confer cisplatin resistance. Finally, transfection of mutant YB-1(E175A) had low impact on overall transcription. The wild type and truncated YB-1(1-205) induced important but different alterations in gene expression as revealed by microarray analyses. Our results indicate that the splicing and the nuclease activities associated with YB-1 have minor impact on cisplatin resistance. In contrast, the global expression profiles displayed by both wild type and truncated YB-1(1-205) revealed several chemoresistance signatures which differed depending on the genetic status of the breast cancer cell line used. PMID:18571458

Guay, David; Evoy, Audrey-Ann; Paquet, Eric; Garand, Chantal; Bachvarova, Magdalena; Bachvarov, Dimcho; Lebel, Michel

2008-01-01

404

New results from the YbF EDM experiment  

NASA Astrophysics Data System (ADS)

The standard model of particle physics predicts that, due to time reversal symmetry, the permanent electric dipole moment (EDM) of the electron is very nearly zero. Many extensions to the standard model predict an electron EDM or other T-violating effects just below current experimental limits, thus there is great interest in new experiments and in improving current experimental precision. I will discuss our recent measurement of the electron EDM using YbF molecules. YbF is particularly sensitive to the electron EDM. This experiment uses a form of laser-radiofrequency double resonance spectroscopy to search for very small energy differences between hyperfine levels in a strong electric field. In addition to describing the experimental and analysis techniques, I will give an overview of the techniques we use to check for systematic errors. I will also describe planned improvements to the experiment which promise several orders of magnitude improvement in sensitivity.

Sauer, B. E.

2013-04-01

405

Growth and spectroscopic properties of Yb:BSO single crystal  

NASA Astrophysics Data System (ADS)

Yb 3+:Bi 4Si 3O 12 crystal up to ?25×120 mm 2 has been grown by the modified vertical Bridgman method. The concentration of Yb 3+ in as-grown crystal was measured by the inductively coupled plasma atomic emission spectrometer (ICP-AES) and the segregation coefficient was calculated as 3.5. The effect of different melt composition for BSO crystal growth will be discussed. The spectral properties have been investigated. The absorption cross section ?a is 2.92×10 -20 cm 2 at 975 nm. The emission cross section ?e is 0.468×10 -20 cm 2 at 1033 nm wavelength. The fluorescence lifetime is 1.01 ms at room temperature.

Zhang, Yan; Xu, Jiayue; Shao, Peifa

2011-03-01

406

Compact nanosecond pulsed single stage Yb-doped fiber amplifier  

NASA Astrophysics Data System (ADS)

In this work we present a compact, nanosecond pulsed, single frequency, single stage Yb-doped fiber amplifier by using an overall fiber core diameter of 20 ?m. The key component is a custom made, compact, ultra-low noise, single frequency ring-cavity solid state laser (SSL) at 1064 nm used as a master oscillator. The SSL can be designed to provide nanosecond pulses with pulse energies in the sub-mJ range. Our ultimate goal is to develop a compact linearly polarized, single frequency, nanosecond pulsed laser source in an all-fiber format. Short (less than 1m), highly Yb-doped fibers have been used in order to suppress non-linear effects.

Balliu, E.; Engholm, M.; Hellström, J.; Elgcrona, G.; Karlsson, H.

2014-02-01

407

Thermal sensor using a tapered Yb-doped fiber amplifier  

NASA Astrophysics Data System (ADS)

We report the numerical investigation of an Yb-doped fiber amplifier with a taper end in order to be used as a thermal sensor. The spectral fluorescence intensity of the Yb-doped fiber is highly modified when the tapered end is subject to different temperatures from 20 to 150°C, and these changes are more sensitive than that presented in untapered doped fibers. This enhanced temperature response is attributed to the taper effects on the temperature dependence of the crosssections of the pump and signal radiations and additional changes of the numerical aperture of the doped tapered core due to temperature. These results can be extrapolated to other doped fibers and contribute with new information for the development of temperature fiber laser sensors.

Viera-González, P.; Toral, D.; Castillo-Guzmán, A.; Guzmán-Ramos, V.; Ceballos-Herrera, D. E.; Selvas-Aguilar, R.

2012-10-01

408

Factors governing Yb magnetism in Yb{sub 0.95}PtIn{sub 2} and other MgCuAl{sub 2}-type structures  

SciTech Connect

The ternary compound 'YbPtIn{sub 2}' has been synthesized and its crystal structure determined using single crystal X-ray diffraction techniques. The compound crystallizes in the MgCuAl{sub 2} structure, a ternary structure type often formed when rare earth metals, Group 10 transition metals, and indium are present in a 1:1:2 ratio. The unit cell is C-centered orthorhombic, space group Cmcm (no. 63) with lattice parameters of a=4.3410(1) A, b=10.3230(2) A, and c=7.8510(2) A. Evidence is found for a substantial non-stoichiometry on the Yb site, in contrast to the Pt and In sites which behave as expected, and it is believed that the stoichiometry of this compound is more properly described as Yb{sub 0.95}PtIn{sub 2}. Magnetic and resistivity measurements reveal that 'YbPtIn{sub 2}' is a weakly interacting, non-magnetic metal exclusively containing Yb{sup 2+}, and with a resistivity ({rho}) varying from 34 {mu}{Omega} cm at room temperature to a residual resistivity {rho}{sub 0} of 23 {mu}{Omega} cm at 1.8 K. Density functional theory calculations suggest that the observed diamagnetic Yb behavior is expected for this compound, but that certain substitutions on the Pt or In site could help stabilize magnetic Yb{sup 3+} and potentially induce heavy fermion behavior. - Graphical abstract: The crystal structure, magnetic behavior, and temperature-dependent resistivity of the new ternary compound Yb{sub 0.95}PtIn{sub 2.} Highlights: Black-Right-Pointing-Pointer Flux growth method used to produce Yb{sub 0.95}PtIn{sub 2} single crystals. Black-Right-Pointing-Pointer Found rare example of non-stoichiometry in a MgCuAl{sub 2}-type structure. Black-Right-Pointing-Pointer The resistivity and diamagnetic response of Yb{sub 0.95}PtIn{sub 2} were modeled. Black-Right-Pointing-Pointer DFT correctly predicts presence of Yb{sup 2+} in Yb{sub 0.95}PtIn{sub 2}. Black-Right-Pointing-Pointer COHP results suggest other MgCuAl{sub 2}-type indides that may contain paramagnetic Yb{sup 3+}.

Malingowski, Andrew C. [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States)] [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Kim, Moosung [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States)] [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Liu, Jue [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States)] [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Wu, Liusuo [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States)] [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Aronson, Meigan C. [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States) [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Khalifah, Peter G., E-mail: kpete@bnl.gov [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

2013-02-15

409

Nuclear YB-1 expression as a negative prognostic marker in nonsmall cell lung cancer.  

PubMed

The human Y-box binding protein, YB-1, is a multifunctional protein that regulates gene expression. Nuclear expression of YB-1 has been associated with chemoresistance and poor prognosis of tumour patients. Representative samples from autopsied material of primary tumours from 77 patients with NSCLC were investigated by immunohistochemistry for subcellular distribution of YB-1 and p53, in order to evaluate the prognostic role of nuclear expression of YB-1. Cytoplasmic YB-1 expression was found in all tumour samples, whereas nuclear expression was only observed in 48%. There was no correlation with histological classification, clinical parameters or tumour size, stage and metastasis status. However, patients with positive nuclear YB-1 expression in tumours showed reduced survival times when compared with patients without nuclear expression. Including information about the histology and mutational status for p53 increased the prognostic value of nuclear YB-1. Patients with nuclear YB-1 expression and p53 mutations had the worst prognosis (median survival 3 months), while best outcome was found in patients with no nuclear YB-1 and wildtype p53 (median survival 15 months). This suggests that the combined analysis of both markers allows a better identification of subgroups with varying prognosis. Nuclear expression of Y-box binding protien seems to be an independent prognostic marker. PMID:14738225

Gessner, C; Woischwill, C; Schumacher, A; Liebers, U; Kuhn, H; Stiehl, P; Jürchott, K; Royer, H D; Witt, C; Wolff, G

2004-01-01

410

Optical properties of PMMA polymer doped with Er3+ and Er3+\\/Yb3+ ions  

Microsoft Academic Search

In this paper we report about fabrication and properties of polymethylmethacrylate doped with Er3+ and Yb3+ ions. The reported layers were fabricated by spin coating onto Si, Si\\/SiO2 or onto glass substrates. For the Er and Yb doping ErCl3 and YbCl3 or ErF3 and YbF3 powder dissolved in C5H9NO or C2H6OS were used. The research was focused on investigation of

V. Prajzler; I. Huttel; O. Lyutakov; J. Spirkova; J. Oswald; Z. Burian; V. Jerabek

2008-01-01

411

Improvement of Yb3+ doped optical fiber preforms by using MCVD method  

NASA Astrophysics Data System (ADS)

This communication describes the fabrication of Yb doped silica preforms by modified chemical vapor deposition (MCVD) method using Yb(C11H19O2)3 and AlCl3 in vapor phase. In order to investigate the optical quality of the preforms a systematic spectroscopic study was carefully carried out on various samples with different Yb and Al doping levels. In this way, the influence of the preforms composition on the Yb spectroscopic properties was studied in details, allowing the prediction of the composition favoring the laser emission with the highest efficiency. The predictions have then been validated after pulling the preforms in large mode area fibers (LMA).

Petit, V.; Sekiya, E. H.; Okazaki, T.; Bacus, R.; Barua, P.; Yao, B.; Ohsono, K.; Saito, K.

2008-05-01

412

Flux Growth of Yb6.6Ir6Sn16 Having Mixed-Valent Ytterbium.  

PubMed

The compound Yb6.6Ir6Sn16 was obtained as single crystals in high yield from the reaction of Yb with Ir and Sn run in excess indium. Single-crystal X-ray diffraction analysis shows that Yb6.6Ir6Sn16 crystallizes in the tetragonal space group P42/nmc with a = b = 9.7105(7) Å and c = 13.7183(11) Å. The crystal structure is composed of a [Ir6Sn16] polyanionic network with cages in which the Yb atoms are embedded. The Yb sublattice features extensive vacancies on one crystallographic site. Magnetic susceptibility measurements on single crystals indicate Curie-Weiss law behavior <100 K with no magnetic ordering down to 2 K. The magnetic moment within the linear region (<100 K) is 3.21 ?B/Yb, which is ?70% of the expected value for a free Yb(3+) ion suggesting the presence of mixed-valent ytterbium atoms. X-ray absorption near edge spectroscopy confirms that Yb6.6Ir6Sn16 exhibits mixed valence. Resistivity and heat capacity measurements for Yb6.6Ir6Sn16 indicate non-Fermi liquid metallic behavior. PMID:24921221

Peter, Sebastian C; Subbarao, Udumula; Rayaprol, Sudhindra; Martin, Joshua B; Balasubramanian, Mahalingam; Malliakas, Christos D; Kanatzidis, Mercouri G

2014-07-01

413

Valence change and magnetic order in YbMn6Ge(6-x)Sn(x).  

PubMed

The YbMn(6)Ge(6-x)Sn(x) compounds (0 < x < 6) have been investigated using x-ray diffraction, magnetic measurements, neutron diffraction and (170)Yb Mössbauer spectroscopy. The YbMn(6)Ge(6-x)Sn(x) system comprises three solid solutions: (i) 0 < x ? 1.1, (ii) 3.2 ? x ? 4.6 and (iii) 5.3 ? x < 6, all of which crystallize in the hexagonal (P6/mmm) HfFe(6)Ge(6)-type structure. The substitution of Sn for Ge yields changes in the type of magnetic order (antiferromagnetic, helimagnetic, ferromagnetic, conical and ferrimagnetic), in the easy magnetization direction (from easy axis to easy plane) as well as in the valence state of Yb (from trivalent to divalent). The Mn moments order at or above room temperature, while magnetic ordering of the Yb sublattice is observed at temperatures up to 110 K. While Yb is trivalent for x ? 1.1 and divalent for x ? 5.3, both magnetic and (170)Yb Mössbauer spectroscopy data suggest that there is a gradual reduction in the average ytterbium valence through the intermediate solid solution (3.2 ? x ? 4.6), and that intermediate valence Yb orders magnetically, a very unusual phenomenon. Analysis of the (170)Yb Mössbauer spectroscopy data suggests that the departure from trivalency starts as early as x = 3.2 and the loss of ytterbium moment is estimated to occur at an average valence of ?2.5+. PMID:21389480

Mazet, T; Ihou-Mouko, H; Ryan, D H; Voyer, C J; Cadogan, J M; Malaman, B

2010-03-24

414

YbPtGe2: A multivalent charge-ordered system with an unusual spin pseudogap  

NASA Astrophysics Data System (ADS)

We performed a study of the structural and physical properties of YbPtGe2. This compound is a multivalent charge-ordered system presenting an unusual spin pseudogap below 200 K. The crystal structure of YbPtGe2 is refined from single-crystal and powder high-resolution synchrotron x-ray diffraction data at different temperatures. Analysis of the structural features of YbPtGe2, together with a combined study of Yb LIII x-ray absorption spectroscopy, magnetic susceptibility ?(T), thermopower S(T), and 171Yb and 195Pt NMR indicate half of the Yb atoms to be in an intermediate valence state with an electronic configuration close to 4f13 (Yb3+), while for the remaining Yb atoms the 4f14 (Yb2+) configuration with almost no valence fluctuations is most likely. A drastic drop of the magnetic susceptibility and a decrease of the isotropic shift 195Kiso(T) with decreasing temperature in the temperature range of 50-200 K evidence the opening of a spin pseudogap with an activation energy of ?/kB ˜ 200 K. Surprisingly, transport properties do not show clear evidence for the opening of a charge gap, thus excluding a standard Kondo-insulator scenario. Possible origins for this unusual electronic (valence) behavior are discussed.

Gumeniuk, Roman; Sarkar, Rajib; Geibel, Christoph; Schnelle, Walter; Paulmann, Carsten; Baenitz, Michael; Tsirlin, Alexander A.; Guritanu, Violeta; Sichelschmidt, Jörg; Grin, Yuri; Leithe-Jasper, Andreas

2012-12-01

415

The Yb-doped aluminosilicate fibers photodarkening mechanism based on the charge-transfer state excitation  

NASA Astrophysics Data System (ADS)

We have studied the photodarkening effect in fiber preforms with an ytterbium-doped aluminosilicate glass core. The room-temperature stable Yb2+ ions formation in the glass matrix under both UV- and NIR-pumping irradiation was revealed by the method of absorption spectra analysis and the fluorescence spectroscopy technique. Comparative studies of preforms and crystals samples luminescence spectra, obtained under UV-excitation, were performed. A general mechanism of Yb2+ ions and aluminium oxygen-hole centers (Al-OHC) formation as a result of photoinduced process of Yb3+ ions excitation to "charge-transfer state" (CTS) was found for both Yb:YAG crystal and aluminosilicate glass.

Rybaltovsky, A. A.; Bobkov, K. K.; Velmiskin, V. V.; Umnikov, A. A.; Shestakova, I. A.; Guryanov, A. N.; Likhachev, M. E.; Bubnov, M. M.; Dianov, E. M.

2014-03-01

416

Er(3+):Yb(3+)-codoped fiber distributed-feedback laser.  

PubMed

We report what is to our knowledge the first fiber distributed-feedback laser using a single Bragg grating at 1.5 microm written directly into a 2-cm-long Er(3+)-doped fiber codoped with Yb(3+). We obtained robust single-frequency operation by either using one end reflector or locally heating the center of the grating to create the necessary phase shift. PMID:19855753

Kringlebotn, J T; Archambault, J L; Reekie, L; Payne, D N

1994-12-15

417

Stopped light with a cryogenic ensemble of Yb173 atoms  

NASA Astrophysics Data System (ADS)

A sample of cryogenically cooled atomic ytterbium is used to create a memory for a classical pulse of light. The information of the light pulse is stored in the nuclear spin of ground-state (1S0) Yb173 (I=5/2). Because nuclear spin states interact very weakly with their environment, the atomic ensemble is resistant to decoherence due to inelastic collisions and inhomogeneous fields, and storage times of hundreds of milliseconds are observed.

Lu, Mei-Ju; Jose, Franklin; Weinstein, Jonathan D.

2010-12-01

418

Cryogenic Yb3+-Doped Solid-State Lasers  

Microsoft Academic Search

Cryogenically cooled solid-state lasers promise a revolution in power scalability while maintaining a good beam quality because of significant improvements in efficiency and thermo-optic properties. This is particularly true for Yb lasers because of their relatively low quantum defect and relatively broadband absorption even at cryogenic temperatures. Thermo-optic properties of host materials, including thermal conductivity, thermal expansion, and refractive index

Tso Yee Fan; Daniel J. Ripin; Roshan L. Aggarwal; Juan R. Ochoa; Bien Chann; Michael Tilleman; Joshua Spitzberg

2007-01-01

419

Yb3+-Doped Four-Wavelength Double Clad Laser  

Microsoft Academic Search

A novel Yb3+-doped four-wavelength double clad fibre laser based on a Fabry-Perot filter, and pumped by a 976 nm laser diode is presented. Its output laser wavelengths are 1085, 1090, 1095 and 1010 nm, respectively. The laser exhibits 0.32 nm line-width, 1.5 W laser output power, 40 dB signal-to-noise ratio and 66% slope efficiency.

Zhao-Wen Xu; Yang Xiang; Ding Ning; Wan-De Fan; Shi-Quan Yang; Shu-Zhong Yuan; Xiao-Yi Dong

2003-01-01

420

Yb-doped Fiber Amplifier at 1015-1030 nm  

Microsoft Academic Search

Many atomic species can only be trapped in magneto-optical traps by the use of UV light generated by non-linear frequency conversion. Fiber amplifiers are ideal sources for the generation of the necessary fundamental wavelength, since they deliver high output power combined with superb beam quality and potentially narrow linewidth. We present simulations and experimental data on a Yb-doped fiber amplifier

Geoffrey Tweedale; Remus Nicolaescu; John T. Stewart; Thomas Walther

2000-01-01

421

Self-association of Transmembrane Domain 2 (TM2), but Not TM1, in Carnitine Palmitoyltransferase 1A  

PubMed Central

Carnitine palmitoyltransferase 1 (CPT1) controls the rate of entry of long-chain fatty acids into the mitochondrial matrix for ?-oxidation and has been reported to exist as an oligomer. We have investigated the in vivo oligomerization of full-length rat CPT1A (rCPT1A) along with those of the N-terminal truncation/deletion mutants ?(1–82), ?(1–18), and ?(19–30) expressed in yeast mitochondria. The data indicate that in liver mitochondria in vivo CPT1A exists as a hexamer but that during preparation and storage of mitochondria the order of oligomerization is rapidly reduced to the trimer, such that a mixture of hexamer and trimer is observed in isolated mitochondria in vitro. Mutants bearing deletions of different segments of the N terminus (including the more N-terminal of the two transmembrane domains) have the same pattern of oligomerization when expressed in yeast mitochondria. The self-association of the individual rCPT1A transmembrane (TM) domains (TM1, TM2) was also studied using the TOXCAT assay (which measures TM self-association in the Escherichia coli inner membrane). There was minimal self-association of the sequence corresponding to TM1 but significant self-association of TM2 in TOXCAT. Chemical cross-linking and analytical ultracent