Note: This page contains sample records for the topic eu tm yb from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

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

2012-06-20

2

Oxide-ion conduction and dielectric relaxation in the fluorite-type Zr0.8Ln0.2O1.9 (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) system  

NASA Astrophysics Data System (ADS)

The electrical conductivity and dielectric properties of the Zr0.8Ln0.2O1.9 (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) system which have a cubic fluorite-type structure were investigated in order to clarify a dynamic property of oxygen vacancy in oxide-ion conductors. The frequency dependences of dielectric constants (epsilonr') were successfully explained by the superposition of Debye-type polarizations and electrolyte-electrode interfacial polarizations. The ac conductivity (?ac) agreed with the calculated values using the dielectric parameters. It was found that the compositional dependence of dielectric properties was similar to that of ?ac.

Kawamoto, Jun-ichi; Yagi, Yuhji; Saito, Miwa; Yamamura, Hiroshi

2011-06-01

3

Syntheses, structure and rare earth metal photoluminescence of new and known isostructural A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) compounds  

SciTech Connect

Nine new A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Tb, Ho, Er, Tm, Yb, Lu) compounds have been synthesized by solid-state reactions. They are isostructural with six reported analogues of yttrium and other lanthanides and the monoclinic unit cell parameters of all fifteen of them vary linearly with the size of A{sup 3+} ion. Single crystal X-ray structures of eight A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Gd, Tb, Ho, Er, Tm) compounds have been determined. Neat A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds exhibit characteristic rare earth metal photoluminescence. -- Graphical abstract: Among the fifteen isostructural A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=rare earth metal) molybdoantimonites, eight (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds exhibit neat characteristic lanthanide photoluminescence in the 200-800 nm range at room temperature. Display Omitted Research highlights: {yields} Syntheses of nine new A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Tb, Ho, Er, Tm, Yb, Lu) compounds. {yields} X-ray structures of eight A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Gd, Tb, Ho, Er, Tm) compounds. {yields} Photoluminescence of neat A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds.

Mohitkar, Shrikant A.; Kalpana, G. [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036 (India); Vidyasagar, K., E-mail: kvsagar@iitm.ac.i [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036 (India)

2011-04-15

4

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

5

Spectroscopic properties of Tm3+ ions in Tm3+\\/Yb3+ codoped tellurite glass  

Microsoft Academic Search

Absorption coefficience of Tm3+ ions in Tm3+\\/Yb3+ codoped tellurite glass have been analyzed by using the J-O theory. The J-O parameters are calculated to be ?2 = 11.11×10?20 cm2, ?4 = 3.5×10?20 cm2 and ?6 = 3.6×10?20 cm2. Spontaneous radiative transition probabilities, branching ratios and radiative life time of Tm3+ ions are also calculated, the calculation results indicate that it

Qingjie Huang; Qingpu Wang; Jun Chang; Xingyu Zhang; Zejin Liu

2009-01-01

6

Infrared luminescence of Tm3+/Yb3+ codoped lanthanum aluminum germanate glasses  

NASA Astrophysics Data System (ADS)

Tm3+ doped and Tm3+/Yb3+ codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd-Ofelt intensity parameters (?2,?4,?6) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm3+ are calculated to evaluate the spectroscopic properties of Tm3+ in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 ?m emission can be greatly enhanced by adding proper amount of Yb3+ under the excitation of 980 nm. The energy transfer processes of Yb3+-Yb3+ and Yb3+-Tm3+ are analyzed, and the results show that Yb3+ ions can transfer their energy to Tm3+ ions with high efficiency and large energy transfer coefficient.

Zhang, Qiang; Chen, Guorong; Zhang, Guang; Qiu, Jianrong; Chen, Danping

2010-01-01

7

Down-Conversion From Blue to Near Infrared in Tm –Yb Codoped Y O Transparent Ceramics  

Microsoft Academic Search

Down-conversion from blue to near infrared (NIR) has been demonstrated in Tm3+-Yb3+ codoped Y2O3 transparent ceramics. Upon the 464-nm excitation, the energy transfer (ET) mechanisms consisted of the Tm3+ : 1G4 ? 2Yb3+ : 2F5\\/2 cooperative down-conversion and the phonon assisted Tm3+ : 1G4 + Yb3+ : 2F7\\/2 ? Tm3+ : 3H5 + Yb3+ : 2F5\\/2 cross relaxation. The low

Hui Lin; Shengming Zhou; Xiaorui Hou; Wenjie Li; Yukun Li; Hao Teng; Tingting Jia

2010-01-01

8

Spectral luminescent properties of Pr{sup 3+}, Sm{sup 3+}, Eu{sup 3+}, Dy{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+}, and Yb{sup 3+} ions in SO{sub 2}Cl{sub 2}-GaCl{sub 3}-LnCl{sub n}  

SciTech Connect

Luminescence spectra of several rare-earth ions (REI) in the sulfurylchloride-galliumchloride system in the IR and visible spectral ranges are studied. The oscillator strengths of the main electronic transitions of the Eu{sup 3+}, Dy{sup 3+}, and Tm{sup 3+} ions in the absorption spectra in the 5000 - 24000 cm{sup {minus}1} region are calculated at 300 K, and on this basis the spectroscopic intensity parameters {tau}{lambda} in the theory of stimulated electric dipole transitions are estimated. On the basis of the data obtained, the main luminescent parameters of the resonance radiative transitions in Pr{sup 3+}, HO{sup 3+}, Er{sup 3+}, and Yb{sup 3+} ions in the SO{sub 2}Cl{sub 2}-GaCl{sub 3}-LnCl{sub n} systems are calculated. 16 refs., 5 figs., 4 tabs.

Batyaev, I.M.; Morev, S.Yu. [Hertzen State Pedagogical Univ., St. Petersburg (Russian Federation)

1995-12-01

9

Spectrum upconversion and downconversion in (Tm3+,Yb3+) and (Tb3+,Yb3+) co-doped fluorosilicate glass  

NASA Astrophysics Data System (ADS)

We investigated the upconversion and downconversion luminescence in (Tb3+, Yb3+) and (Tb3+, Yb3+) co-doped lithiumlanthanum- aluminosilicate oxyfluoride glass. Upon excitation at 980 nm, where crystalline CdTe solar cells no longer absorb, the sub-bandgap photons can be converted to the higher-energy ones via upconversion. In addition, under excitation between 470 nm and 490 nm, one blue photon might be split up to two near-infrared ones via downconversion. The downconversion luminescence matches the spectral response of crystalline Si solar cell well. We observed much more intense upconversion luminescence from (Tm3+, Yb3+) codoped glass than that from ( Tb3+, Yb3+) codoped glass under the same 980 nm excitation conditions. Our results indicate that the sequential energy transfer from Yb3+ ions to Tm3+ ions is much more efficient than the cooperative energy transfer from Yb3+ ions to Tb3+ ions.

Pan, Z.; Akrobetu, R.; Morgan, S. H.

2013-09-01

10

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

11

Near-infrared quantum cutting in YPO4:Yb3+, Tm3+ via cooperative energy transfer  

NASA Astrophysics Data System (ADS)

The experimental evidences of the cooperative energy transfer from Tm3+ to Yb3+ have been presented by the photoluminescence properties of YPO4:Yb3+, Tm3+, and the decay lifetime curves of the 1G4 emission of Tm3+. Near-infrared quantum cutting involving the 2F5/2-->2F7/2 emission of Yb3+ (about 970-1010 nm) is achieved upon the excitation of 1G4 energy level of Tm3+ at 474 nm. Quantum efficiency related to Yb3+ concentration is calculated, and the maximum efficiency reaches 172.8%. Because the energy of Yb3+ transition is matched with the band gap of the crystalline Si, the phosphors could be applied potentially in silicon-based solar cells.

Xie, Lechun; Wang, Yuhua; Zhang, Huijuan

2009-02-01

12

Solvothermal syntheses, and characterization of [Ln(en){sub 4}(SbSe{sub 4})] (Ln=Ce, Pr) and [Ln(en){sub 4}]SbSe{sub 4}.0.5en (Ln=Eu, Gd, Er, Tm, Yb): The effect of lanthanide contraction on the crystal structures of lanthanide selenidoantimonates(V)  

SciTech Connect

Two types of lanthanide selenidoantimonates [Ln(en){sub 4}(SbSe{sub 4})] (Ln=Ce(1a), Pr(1b)) and [Ln(en){sub 4}]SbSe{sub 4}.0.5en (Ln=Eu(2a), Gd(2b), Er(2c), Tm(2d), Yb(2e); en=ethylenediamine) were solvothermally synthesized by reactions of LnCl{sub 3}, Sb and Se with the stoichiometric ratio in en solvent at 140 deg. C. The four-en coordinated lanthanide complex cation [Ln(en){sub 4}]{sup 3+} formed in situ balances the charge of SbSe{sub 4}{sup 3-} anion. In compounds 1a and 1b, the SbSe{sub 4}{sup 3-} anion act as a monodentate ligand to coordinate complex [Ln(en){sub 4}]{sup 3+} and the neutral compound [Ln(en){sub 4}(SbSe{sub 4})] is formed. The Ln{sup 3+} ion has a nine-coordinated environment involving eight N atoms and one Se atom forming a distorted monocapped square antiprism. In 2a-2e the lanthanide(III) ion exists as isolated complex [Ln(en){sub 4}]{sup 3+}, in which the Ln{sup 3+} ion is in a bicapped trigonal prism geometry. A systematic investigation of the crystal structures reveals that two types of structural features of these lanthanide selenidoantimonates are related with lanthanides contraction across the lanthanide series. TG curves show that compounds 1a-1b and 2a-2e remove their organic components in one and two steps, respectively. - Graphical abstract: Two types of lanthanide selenidoantimonates [Ln(en){sub 4}(SbSe{sub 4})] (Ln=Ce, Pr) and [Ln(en){sub 4}]SbSe{sub 4}.0.5en (Ln=Eu, Gd, Er, Tm, Yb; en=ethylenediamine) have been synthesized under the mild solvothermal conditions, and a systematic investigation of the crystal structures reveals that two types of structural features of these lanthanide selenidoantimonates are related with lanthanides contraction across the lanthanide series.

Jia Dingxian [School of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215123 (China)], E-mail: jiadingxian@suda.edu.cn; Zhu Aimei; Jin Qinyan; Zhang Yong; Jiang Wenqing [School of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215123 (China)

2008-09-15

13

Thermal expansion, heat capacity and magnetostriction of RAl3 (R = Tm, Yb, Lu) single crystals  

NASA Astrophysics Data System (ADS)

We present thermal expansion and longitudinal magnetostriction data for cubic RAl3 (R = Tm, Yb, Lu) single crystals. The thermal expansion coefficient for YbAl3 is consistent with an intermediate valence of the Yb ion, whereas the data for TmAl3 show crystal electric field contributions and have strong magnetic field dependencies. de Haas-van Alphen-like oscillations were observed in the magnetostriction data of YbAl3 and LuAl3, several new extreme orbits were measured and their effective masses were estimated. Zero and 140 kOe specific heat data taken on both LuAl3 and TmAl3 for T < 200 K allow for the determination of a CEF splitting scheme for TmAl3.

Bud'Ko, S. L.; Frederick, J. C.; Mun, E. D.; Canfield, P. C.; Schmiedeshoff, G. M.

2008-01-01

14

Upconversion luminescence and mechanisms in Yb 3+-sensitized Tm 3+-doped oxyhalide tellurite glasses  

Microsoft Academic Search

Effect of Yb2O3 content on upconversion luminescence and mechanisms in Yb3+-sensitized Tm3+-doped oxyhalide tellurite glasses were investigated under 980nm excitation. Intense blue and relatively weak red upconversion emission centered at 476 and 649nm corresponding to the transitions 1G4?3H6 and 1G4?3H4 of Tm3+, respectively, are simultaneously observed at room temperature. The results show that upconversion blue and red emission intensities of

Shiqing Xu; Hongping Ma; Dawei Fang; Zaixuan Zhang; Zhonghong Jiang

2006-01-01

15

Infrared luminescence of Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate glasses  

SciTech Connect

Tm{sup 3+} doped and Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd-Ofelt intensity parameters ({Omega}{sub 2},{Omega}{sub 4},{Omega}{sub 6}) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm{sup 3+} are calculated to evaluate the spectroscopic properties of Tm{sup 3+} in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 {mu}m emission can be greatly enhanced by adding proper amount of Yb{sup 3+} under the excitation of 980 nm. The energy transfer processes of Yb{sup 3+}-Yb{sup 3+} and Yb{sup 3+}-Tm{sup 3+} are analyzed, and the results show that Yb{sup 3+} ions can transfer their energy to Tm{sup 3+} ions with high efficiency and large energy transfer coefficient.

Zhang Qiang; Zhang Guang [Key Laboratory of Material Science and Technology for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Chen Guorong [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Qiu Jianrong [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Chen Danping [Key Laboratory of Material Science and Technology for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

2010-01-15

16

Evidence of Tm impact in low-photodarkening Yb-doped fibers.  

PubMed

In contrast to Yb/Al-doped fibers, the influence of very low Tm(2)O(3) concentrations (? 0.1 mol-ppm) on photodarkening (PD) is clearly detectable in Yb/P-doped fibers that are known to show little degradation effects. For Tm(2)O(3) additions of more than 50 mol-ppm, the measured PD loss is even similar to Yb/Al-doped fibers with comparable rare earth concentrations. Our work reveals the risk of color center generation by pumping at wavelengths of 915 nm or 976 nm even in Al-free Yb-doped fibers and emphasizes the importance of high purity of raw materials for the preparation of Yb laser fibers with expected very low PD. PMID:23546142

Jetschke, Sylvia; Unger, Sonja; Schwuchow, Anka; Leich, Martin; Fiebrandt, Julia; Jäger, Matthias; Kirchhof, Johannes

2013-03-25

17

Blue upconversion luminescence in Tm^(3+)/Yb^(3+) co-doped new oxyfluoride tellurite glass  

NASA Astrophysics Data System (ADS)

The thermal stability, Raman spectrum and upconversion properties of Tm^(3+)/Yb^(3+) co-doped new oxyfluoride tellurite glass are investigated. The results show that Tm^(3+)/Yb^(3+) co-doped oxyfluoride tellurite glass possesses good thermal stability, lower phonon energy, and intense upconversion blue luminescence. Under 980-nm laser diode (LD) excitation, the intense blue (475 nm) emission and weak red (649 nm) emission corresponding to the 1G4 -> 3H6 and 1G4 -> 3F4 transitions of Tm^(3+) ions respectively, were simultaneously observed at room temperature. The possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Tm^(3+)/Yb^(3+) co-doped oxyfluoride tellurite glass can be used as potential host material for the development of blue upconversion optical devices.

Xu, Shiqing; Ma, Hongping; Fang, Dawei; Zhang, Zaixuan; Hu, Lili; Jiang, Zhonghong

2005-09-01

18

Magnetic and Electrical Properties, 151Eu Mössbauer Spectroscopy, and Chemical Bonding of REAgMg ( RE=La, Ce, Eu, Yb) and EuAuMg  

Microsoft Academic Search

Single-phase samples of REAgMg (RE=La, Ce, Eu, Yb) and EuAuMg were prepared by reacting the elements in sealed tantalum tubes in a high-frequency furnace. LaAgMg and CeAgMg adopt the hexagonal ZrNiAl-type structure, while EuAgMg, YbAgMg, and EuAuMg crystallize with the orthorhombic TiNiSi type. Chemical bonding was exemplarily investigatedfor EuAgMg and EuAuMg on the basis of TB-LMTO-ASAcalculations. Magnetic susceptibility measurements indicatePauli

Dirk Johrendt; Gunter Kotzyba; Henning Trill; Bernd D. Mosel; Hellmut Eckert; Thomas Fickenscher

2002-01-01

19

Monodisperse and core–shell structured NaYF 4:Ln@SiO 2 (Ln = Yb\\/Er, Yb\\/Tm) microspheres: Synthesis and characterization  

Microsoft Academic Search

In this paper, the core–shell structured NaYF4:Yb\\/Er@SiO2 and NaYF4:Yb\\/Tm@SiO2 microspheres were prepared by coating the NaYF4:Yb\\/Er and NaYF4:Yb\\/Tm phosphors on the surface of monodisperse silica via a facile colloid thermolysis process, respectively. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, Fourier transform IR spectroscopy, and photoluminescence were applied to characterize these samples. The obtained core–shell structured NaYF4:Ln@SiO2

Shuyuan Tan; Piaoping Yang; Na Niu; Shili Gai; Jun Wang; Xiaoyan Jing; Jun Lin

2010-01-01

20

Sol–gel Eu 3+\\/Tm 3+ doped transparent glass–ceramic waveguides  

Microsoft Academic Search

Eu3+ and Tm3+ doped lanthanum fluoride and lanthanum oxyfluoride are obtained from Eu3+, Tm3+ containing lanthanum fluoracetate solutions. The nature of the crystal phase obtained could be controlled by the temperature of heat treatment. Spectral characteristics of Eu3+ doped crystal phases were sufficiently different to allow utilization of Eu3+ as structural probes. Tm3+ emission at the technologically important spectral region

S. J. L. Ribeiro; C. C. Araújo; L. A. Bueno; R. R. Gonçalves; Y. Messaddeq

2004-01-01

21

(Ho, Tm, Yb): KLuW nanoparticles, an efficient thermometry sensor in the biological range  

NASA Astrophysics Data System (ADS)

We studied up-conversion emission of triply doped (Ho,Tm,Yb):KLu(WO4)2 (KLuW) nanocrystals at the range of temperature 296-673 K at different excitation wavelengths. The intensity ratio between two emission lines was used for monitoring the temperature. Pumping Yb3+ at 980 nm provides a good response at relatively high temperatures, while pumping Tm3+ at 802 nm provides an excellent sensitivity in the biological range of temperatures., which make the material also attractive for biological temperature sensors.

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

2013-02-01

22

Relaxation of excited states of Tm3+ and Tm3+-Eu3+ energy transfer in YVO4 crystal  

NASA Astrophysics Data System (ADS)

Tm3+-Eu3+ energy transfer processes and relaxation dynamics of the 3 H 4 and 3 F 4 excited states of Tm3+ ions in 1 at. % Tm3+, 5 at. % Eu3+:YVO4 single crystal were studied. Contribution of Tm3+-Eu3+ energy transfer reduces effectively the lifetime of terminal level in a potential 3 H 4-3 F 4 laser transition at around 1.48 ?m. Adverse quenching of the 3 H 4 emission by Eu3+ ions is found to be less efficient than that reported for Tm3+ + Tb3+ system in YVO4. The classical Inokuti-Hirayama model accounts well for an experimental decay curve of the 3 H 4 emission recorded for co-doped crystal. Stimulated emission cross section for 3 H 4-3 F 4 transition of Tm3+ at around 1.48 ?m was analyzed taking into account the anisotropy of YVO4 crystal.

Lisiecki, R.; Ryba-Romanowski, W.; ?ukasiewicz, T.

2006-05-01

23

Thermal lens study of energy transfer in Yb3+/Tm3+-co-doped glasses  

NASA Astrophysics Data System (ADS)

Energy transfer (ET) and heat generation processes in Yb3+/Tm3+-co-doped low-silica calcium-aluminosilicate glasses were investigated using thermal lens and photoluminescence measurements. Stepwise ET processes from Yb3+ to Tm3+, with excitation at 0.976 ?m, produced efficient emission in the mid-infrared range at around 1.8 ?m, with high fluorescence quantum efficiency (~0.50) and relatively low thermal loading (?0.42). An equation was deduced for the description of the thermal lens results which provided the absolute value of the ET efficiency and optimal Tm3+ concentration that result in population of the 1.8 ?m Tm3+ emitting level. These results suggest that the studied co-doped system would be a promising candidate for the construction of high-power diode-pumped solid-state lasers in the mid-infrared range, which are especially important for the purpose of medical procedures.

Jacinto, C.; Vermelho, Marcos V.; de Araujo, M. T.; Udo, P. T.; Astrath, N. G.; Bento, A. C.; Catunda, T.; Baesso, M. L.

2007-07-01

24

Energy transfer rates of KY3F10:Yb:Nd:Tm crystals  

Microsoft Academic Search

In this work we present the spectroscopic properties of KY3F10 (KY3F) single crystals doped with thulium and also co-doped with ytterbium and\\/or neodymium, KY3F:Yb:Nd:Tm and KY3F:Nd:Tm. The most important processes that lead to the thulium up conversion emissions were identified. The absorption spectra of the samples were measured at room temperature in the range of 200 nm-1200 nm. The emission

L. C. Courrol; H. M. S. M. D. Linhares; A. F. H. Librantz; S. L. Baldochi; L. Gomes; I. M. Ranieri

2010-01-01

25

Dopant distribution in a Tm3+-Yb3+ codoped silica based glass ceramic: An infrared-laser induced upconversion study  

NASA Astrophysics Data System (ADS)

The optically active dopant distribution in a Tm3+-Yb3+ doped silica based glass ceramic sample has been investigated. A systematic analysis of the upconversion fluorescence of the Tm3+-Yb3+ codoped glass and glass ceramic has been performed at room temperature. Tm3+ and Yb3+ single doped glass and glass ceramics have also been included in the study. Upon infrared excitation at 790 nm into the 3H4 level of the Tm3+ ions a blue upconversion emission is observed, which is drastically increased in the Yb3+ codoped samples. A rate equation model confirmed the energy transfer upconversion mechanism. Based on these results, the temporal dynamic curves of the levels involved in the upconversion process, 3H4, 2F5/2, and 1G4 were interpreted in the glass ceramic samples. The contribution of the optically active Tm3+ and Yb3+ ions in the crystalline and in the vitreous phase of the glass ceramic was distinguished and the ratio of Tm3+ ions in the crystalline phase could be quantified for the 1 mol % Tm3+-2.5 mol % Yb3+ glass ceramic. A surprising result was obtained for that concentration: the main contribution to the upconversion emission of the glass ceramic is due to Tm3+-Yb3+ ions in the vitreous phase.

Lahoz, F.; Martín, I. R.; Méndez-Ramos, J.; Núñez, P.

2004-04-01

26

Complexation of trivalent rare earth elements (Ce, Eu, Gd, Tb, Yb) by carbonate ions  

Microsoft Academic Search

Carbonate stability constants for five rare earth elements (Ce[sup 3+], Eu[sup 3+], Gd[sup 3+], Tb[sup 3+], and Yb[sup 3+]) have been determined at t = 25[degrees]C and 0.70 [plus minus] 0.02 M ionic strength through solvent exchange techniques. Estimated stability constants for Ce, Eu, and Yb are in close agreement with previous work. Analyses using Gd and Tb provide the

Jong Hyeon Lee; R. H. Byrne

1993-01-01

27

Tm Doped Fiber Laser Pumped by a Cladding-Pumped Er, Yb Fiber Laser.  

National Technical Information Service (NTIS)

This report results from a contract tasking University of Southampton as follows: The Grantee will investigate (a) optimization of the cladding- pumped Er-Yb doped fiber laser (EYDFL) for efficient pumping of Tm- doped fibers. (b) Investigation of core-pu...

W. A. Clarkson

2006-01-01

28

Magnetic Anisotropy of R2Co17 Compounds (R = Er, Tm, Yb).  

National Technical Information Service (NTIS)

Saturation moments, easy direction of magnetization, anisotropy field, and anisotropy constants have been determined at 4.2K and room temperature for Er2Co17, Tm2Co17 and Yb2Co17. The data obtained are compared with theoretical predictions. Y and Pr were ...

K. S. V. L. Narasimhan W. E. Wallace R. D. Hutchens J. E. Greedan

1974-01-01

29

Intense red upconversion luminescence from Tm3+/Yb3+ codoped transparent glass ceramic.  

PubMed

Tm3+/Yb3+ codoped transparent glass ceramic containing ?-PbF2 nanocrystals was successfully prepared. After thermal treatment, emissions from the state of Tm3+ excited by 980 nm laser were greatly quenched by cross relaxation and the 700 nm luminescence from Tm3+:3F2,3?3H6 transition was strongly enhanced. A nearly monochromatic red luminescence band was observed. Based on the luminescence decay curves and Judd-Ofelt analysis, the strengthened cross relaxation played an important role in such phenomenon. PMID:22854468

Xu, Wei; Chen, Jianmin; Wang, Peng; Zhang, Zhiguo; Cao, Wenwu

2012-01-15

30

A new series of lanthanoid containing Keggin-type germanotungstates with acetate chelators: [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} {l_brace}Ln=Eu{sup III}, Gd{sup III}, Tb{sup III}, Dy{sup III}, Ho{sup III}, Er{sup III}, Tm{sup III}, and Yb{sup III{r_brace}}  

SciTech Connect

A series of head-on complexes of lanthanoid containing germanotungstates was isolated from a one pot reaction in an acetate buffer at pH 4.5. This convenient approach brought forward the [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} (Ln=Eu{sup III}, Gd{sup III}, Tb{sup III}, Dy{sup III}, Ho{sup III}, Er{sup III}, Tm{sup III}, and Yb{sup III}) family with acetate chelators in the rarely observed {mu}{sub 2}: {eta}{sup 2}-{eta}{sup 1} mode. All compounds were structurally characterized using various solid state analytics, such as single crystal X-ray diffraction, FT-IR spectroscopy, and thermogravimetric analysis. The isostructural polyanions crystallize in the monoclinic system (S.G. P2{sub 1}/c). Temperature-dependent magnetic susceptibility measurements were performed on the Gd{sup III}-complex which exhibits near perfect Curie-type behavior. -- Graphical abstract: A new series of acetate-chelated lanthanoid containing germanotungstates [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} (Ln=Eu to Yb) is available from a convenient one-pot reaction. The influence of the lanthanide contraction on the structural properties is discussed and the magnetic properties of the Gd-representative are investigated in detail. Display Omitted Research Highlights: {yields}Lanthanoid containing germanotungstates with acetate chelators in {mu}{sub 2} : {eta}{sup 2}-{eta}{sup 1} mode. {yields}Lanthanoid contraction in [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} (Ln=Eu{sup III}-Yb{sup III}). {yields}Facile one-pot synthesis of the lanthanoid containing germanotungstate series.

Hussain, Firasat; Sandriesser, Stefan [Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland); Speldrich, Manfred [Institute of Inorganic Chemistry, RWTH Aachen University, D-52074 Aachen (Germany); Patzke, Greta R., E-mail: greta.patzke@aci.uzh.c [Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland)

2011-01-15

31

[Upconversion luminescence properties of ZBLAN : Nd3+, Tm3+, Yb3+].  

PubMed

The ZBLAN : Nd3+, Tm3+, Yb3+ upconversion materials were prepared by high-temperature solid method. The concentrations of Tm3+ and Yb3+ were 0.01% and 0.3% respectively. The concentration of Nd3+ changed in the range from 0.1% to 2%. The absorption spectrum of ZBLAN : Nd3+, Tm3+, Yb3 in all samples from 300 to 1 000 nm was measured at room temperature. The upconversion emission was observed when excited by 798 nm infrared light. The material samples emitted relatively strong multi-band (the red, blue and green color) visible light. Based on the experiment, the multi-band visible spectral lines were analyzed, and the energy level transition mechanism was given. The blue light results from the transition of 1G4 --> 3 H6 of Tm3+, the green light is from the transition of 2 H7/2 --> 4 I9/2 of Nd3+, and the red light originates from the transition of 2 H11/2 --> I9/2 of Nd3+. The results show that the upconversion mechanism includes excited state absorption, energy transfer, cross relaxation and so on. The energy transfer processes between Nd3+, Tm3+ and Yb3+ ions both forward and backward prove to be the origin of upconversion emissions. The effect of rare earth doping concentration on the energy upconversion efficiency was analyzed, according to the different upconversion light emitting intensity from samples with different Tm3+ mol concentrations. The upconversion luminescence increased with the Nd3+ concentration and got its peak at 1.5%. PMID:19810515

Yang, Zhi-Ping; Du, Hai-Yan; Sun, Jia-Yue; Wang, Wei

2009-06-01

32

Blue and red emission in wide band gap BaZrO 3:Yb 3+,Tm 3+  

Microsoft Academic Search

Under NIR excitation at 967 intense blue and red photoluminescence (PL) emissions are observed at room temperature in codoped Tm3+–Yb3+ barium zirconate (BaZrO3:Yb,Tm) powders. Powders were prepared by a simple hydrothermal method, and present a wide band gap that depends on the total rare earth content due to the degree of disorder induced in the BaZrO3 lattice by the substitution

R. Borja-Urby; L. A. Diaz-Torres; P. Salas; M. Vega-Gonzalez; C. Angeles-Chavez

2010-01-01

33

Up-conversion fluorescence of Tm3+ and Gd3+ in Yb3+/Tm3+ co-doped Gd2O3 nanocrystals.  

PubMed

Through a co-precipitation method Gd(OH)3:20%Yb3+, 1%Tm3+ nanorods were synthesized. After sintered at 900 degrees C for 1 h in air, the as-prepared Gd(OH)3:20%Yb3+, 1%Tm3+ nanorods were converted into Gd2O3:20%Yb3+, 1% Tm3+ nanocrystals. Crystalline phases, sizes, and morphologies of the two samples were characterized by X-ray diffraction and field emission scanning electron microscope. The up-conversion (UC) fluorescence spectra of the Gd2O3:20%Yb3+, 1%Tm3+ nanocrystals were recorded by using a fluorescence spectrophotometer with a 980 nm continuous wave laser diode as excitation source. The nanocrystals not only present characteristic blue and ultraviolet (UV) UC emissions of activated Tm3+, but also show UV UC emissions of host Gd3+. The experimental study suggests that the excitation power has great effects on UC fluorescence properties and the energy transfer from Tm3+ to Gd3+ is very efficient. PMID:22413275

Cao, Chunyan

2011-11-01

34

Tuning from blue to magenta the up-converted emissions of YF3:Tm3+/Yb3+ nanocrystals.  

PubMed

Monodisperse YF3:Tm3+/Yb3+ nanocrystals have been synthesized to explore the visible up-converting properties under near infrared (975 nm) excitation. It has been found that the nanoparticles exhibit intense red up-converted emissions, in addition to the characteristic UV and blue Tm3+-bands. It is demonstrated that, by carefully selecting Tm3+ and Yb3+ contents, the relative intensity of the different emissions can be changed producing an overall emission colour that can be tuned from blue to magenta. PMID:21152607

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

2010-12-13

35

Trapping processes in CaS:Eu{sup 2+},Tm{sup 3+}  

SciTech Connect

CaS:Eu{sup 2+},Tm{sup 3+} is a persistent red phosphor. Thermoluminescence was measured under different excitation and thermal treatment conditions. The results reveal that the charge defects, created by substituting Tm{sup 3+} for Ca{sup 2+}, serve as hole traps for the afterglow at room temperature. Tm{sup 3+} plays the role of deep electron trapping centers, capturing electrons either through the conduction band or directly from the excited Eu{sup 2+} ions. These two processes, in which two different sites of Tm{sup 3+} are involved, correspond to two traps with different depths. (c) 2000 American Institute of Physics.

Jia, Dongdong [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China); Jia, Weiyi [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico); Evans, D. R. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States); Dennis, W. M. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States); Liu, Huimin [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico); Zhu, Jing [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China); Yen, W. M. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States)

2000-09-15

36

Synthesis of colloidal upconverting NaYF4: Er3+/Yb3+ and Tm3+/Yb3+ monodisperse nanocrystals.  

PubMed

The synthesis, characterization, and spectroscopy of upconverting lanthanide-doped NaYF4 nanocrystals (NCs) is presented. The monodisperse cubic NaYF4 NCs were synthesized via a thermal decomposition reaction of trifluoroacetate precusors in a mixture of technical grade chemicals, octadecene and the coordinating ligand oleic acid. In this straightforward method, the dissolved precursors are added slowly to the reaction solution through a stainless-steel canula resulting in highly luminescent nanocrystals with an almost monodisperse particle size distribution. The NCs were characterized through the use of transmission electron microscopy, selected area electron diffraction, 1H NMR, powder X-ray diffraction, and high-resolution luminescence spectroscopy. The NaYF4 NCs are capable of being of dispersed in nonpolar organic solvents thus forming colloidally stable solutions. The colloids of the Er3+, Yb3+ and Tm3+, Yb3+ doped NCs exhibit green/red and blue upconversion luminescence, respectively, under 980 nm laser diode excitation with low power densities. PMID:17302461

Boyer, John-Christopher; Cuccia, Louis A; Capobianco, John A

2007-02-16

37

Synthesis and upconversion luminescence properties of CaF2:Yb3+/Tm3+ microspheres.  

PubMed

CaF2:Yb3+/Tm3+ microspheres were synthesized by using a simple hydrothermal method. Their structures and morphologies were characterized by X-ray diffraction (XRD) and field-effective scanning electron microscopy (FESEM). The microspheres were formed from a large number of nanospheres with almost the same diameter after annealing. The growth mechanism of the microspheres was discussed. Strong ultraviolet (UV) and blue upconversion (UC) emission from the CaF2 microspheres was observed under 980 nm excitation. The enhancement of the UV UC emission was attributed to the size effect of the nanoscale particles. PMID:22413321

Jiang, Tao; Zhao, Dan; Qin, Weiping

2011-11-01

38

Thermal expansion and magnetostriction in RAl3 (R = Tm,Yb,Lu) single crystals  

NASA Astrophysics Data System (ADS)

We present temperature dependent thermal expansion and low temperature longitudinal magnetostriction measurements taken using a capacitance dilatometer [G.M. Schmiedeshoff et al., RSI, in press] in a PPMS-14 instrument for several cubic RAl3 (R = rare earth) compounds. Quantum oscillations in the magnetostriction were observed in LuAl3 and YbAl3, including few new frequences for the latter. Data on qualitative changes in TmAl3 thermal expansion in presence of the longitudinal magnetic field will be presented and discussed.

Bud'Ko, S. L.; Frederick, J.; Canfield, P. C.; Schmiedeshoff, G. M.

2007-03-01

39

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

2011-01-14

40

Blue Upconversion Luminescence in Tm3+/Yb3+ Codoped CaWO4 Polycrystals  

NASA Astrophysics Data System (ADS)

We investigate the upconversion emission of CaWO4:Tm3+/Yb3+ polycrystals prepared by the high-temperature solid-state method. The crystal structure of the polycrystals is characterized by means of x-ray diffraction. Under the excitation of a 980 nm continuous wave diode laser, the samples show intense blue upconversion emissions centered at 473 nm, corresponding to the 1G4?3H6 transition of Tm3+. The dependence of the upconversion emission intensity on the pump power of a laser diode is measured, and the results indicate that the two-photon and three-photon processes contribute simultaneously to the blue upconversion emissions. The possible multi-photon upconversion process and upconversion mechanisms are discussed.

Xu, Yan-Ling; Wang, Yun-Long; Shi, Lian-Sheng; Tan, Xiang

2013-08-01

41

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

42

Codopant ion-induced tunable upconversion emission in ?-NaYF4:Yb3+/Tm3+ nanorods.  

PubMed

An innovative route to tune upconversion (UC) emission in ?-NaYF(4):Yb(3+)/Tm(3+) nanorods through codoping a third rare-earth ion upon continuous wave excitation near 976 nm is reported. The dependence of UC emission on codopant concentration and environment temperature shows that tailored local environment and readjustable depopulation of excited-state ions are responsible for the tuning of UC luminescence. Codopant ions introduce a new distribution of active ions and a modified distance between Tm(3+) and Yb(3+) ions, making UC systems more sensitive to impurity ions than downconversion systems. PMID:23165284

Gao, Dangli; Zhang, Xiangyu; Zheng, Hairong; Shi, Peng; Li, Long; Ling, Yawen

2012-11-20

43

Luminescence properties of Y 2O 3 single crystals doped with Pr 3+ or Tm 3+ and codoped with Yb 3+, Tb 3+ or Ho 3+ ions  

Microsoft Academic Search

We have recorded fluorescence spectra and measured fluorescence lifetimes in yttria (Y2O3) single crystals doped with only Tm3+ or Pr3+ ions or codoped with Yb3+, Tb3+ or Ho3+ ions. The crystals were grown in the form of crystal fibers by using the laser heated pedestal growth (LHPG) technique. The codoped (Yb, Tm) and (Yb, Pr) crystals were studied for their

Y. Guyot; R. Moncorgé; L. D. Merkle; A. Pinto; B. McIntosh; H. Verdun

1996-01-01

44

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

45

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

46

Adsorption of several actinide (Th, U) and lanthanide (La, Eu, Yb) ions by Mycobacterium smegmatis  

Microsoft Academic Search

Adsorption measurements of several actinide [thorium (Th), uranium (U)] and lanthanide [lanthanum (La), europium (Eu), ytterbium (Yb)] cations by Mycobacterium smegmatis showed that sorption kinetics followed a three-phase pattern. For 5% (w\\/w) bacterial suspensions at pH 1, maximum cation biosorption per gram dry biomass corresponded to 170 µmol Th4+ and 187 µmol UOinf2sup2+. Adsorption of all cations studied obeyed the

Yves Andres; H. John MacCordick; Jean-Claude Hubert

1993-01-01

47

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

48

Selective biosorption of lanthanide (La, Eu, Yb) ions by Pseudomonas aeruginosa  

SciTech Connect

The ability of Pseudomonas aeruginosa to adsorb selectively La{sup 3+}, Eu{sup 3+}, and Yb{sup 3+} from aqueous solution was investigated. The lanthanide biosorption equilibrium obeyed the Brunauer-Emmett-Teller isotherm model, indicating multilayer adsorption. Determined levels of maximum adsorption capacities were 397 {micro}mol/g for lanthanum, 290 {micro}mol/g for europium and 326 {micro}mol/g for ytterbium. The results indicated that there were about 100 preferential sites for lanthanum per g of dry biomass. Experiments with mixed-cation solutions showed that the sequence of preferential biosorption was Eu{sup 3+} = Yb{sup 3+} > La{sup 3+}. Biomass dried at 37 and 70 C showed the same selective behavior as wet biomass. Inert microbial biomass dried at 37 C appeared to be the most efficient form for experimental use. The uptake of lanthanide by P. aeruginosa cells was not affected by the presence of sodium, potassium, calcium, chloride, sulfate and nitrate ions. Aluminum was a strong inhibitor of lanthanide ions biosorption. 87% of the total Al{sup 3+} was removed from the 3 mM solution, whereas only 8%, 20% and 3% of the total La{sup 3+}, Eu{sup 3+}, and Yb{sup 3+}, respectively, were sorbed from 3 mM solutions. The results suggested that cells of Pseudomonas aeruginosa may find promising applications for removal and separation of lanthanide ions from aqueous effluents.

Texier, A.C.; Andres, Y.; Cloirec, P. le [Ecole des Mines de Nantes (France)

1999-02-01

49

Gain improvement by internal laser cavity in Tm3+Yb3+-co-doped tellurite fiber amplifier pumped by 980-nm laser  

NASA Astrophysics Data System (ADS)

S-band Tm3+/Yb3+ co-doped tellurite fiber amplifier pumped by a 980 nm laser diode is proposed and modeled taking into consideration of the energy transfer process from Yb3+ to Tm3+ and the laser cavity inside a co-doped fiber amplifier. S-band spectral gains for the co-doped fiber amplifiers are investigated. The results show that considerable gain improvement can be achieved by constructing 1050nm laser cavity inside the amplifier.

Chang, Jun; Wang, Qingpu; Peng, Gangding; Zhang, Xingyu; Liu, Zejin; Ding, Shuanghong; Liu, Zhaojun; Zhang, Sasa; Wang, Gongtang

2006-09-01

50

Properties of single crystalline AZn2Sb2 (A = Ca,Eu,Yb)  

NASA Astrophysics Data System (ADS)

Single crystals of CaZn2Sb2, EuZn2Sb2, and YbZn2Sb2 were grown from melts of nominal composition AZn5Sb5 (A = Ca,Eu,Yb) with the excess melt being removed at 1073 K. The electrical transport properties are consistent with those previously reported for polycrystalline samples. This confirms that the p-type carrier concentrations ranging from 2 × 1019 cm-3 to ~1 × 1020 cm-3 are intrinsic to these materials. Also consistent with transport in polycrystalline materials, the carrier mobility is found to be lowest in CaZn2Sb2, suggesting the trends in mobility and thermoelectric efficiency within these compounds are inherent to the material systems and not due to inhomogeneity or impurities in polycrystalline samples. These results suggest CaZn2Sb2 has the strongest coupling between the doping/defects and the electronic framework. Magnetization measurements reveal an antiferromagnetic transition near 13 K in EuZn2Sb2, and the observed magnetic anisotropy indicates the spins align parallel and anti-parallel to c in the trigonal lattice. Powder neutron diffraction on polycrystalline samples of CaZn2Sb2 and YbZn2Sb2 reveals smooth lattice expansion to 1000 K, with c expanding faster than a. The Debye temperatures calculated from specific heat capacity data and the isotropic displacement parameters are found to correlate with the carrier mobility, with the CaZn2Sb2 displaying the largest Debye temperature and smallest mobility.

May, Andrew F.; McGuire, Michael A.; Ma, Jie; Delaire, Olivier; Huq, Ashfia; Custelcean, Radu

2012-02-01

51

Properties of single crystalline AZn2Sb2 (A=Ca,Eu,Yb)  

SciTech Connect

Single crystals of CaZn{sub 2}Sb{sub 2}, EuZn{sub 2}Sb{sub 2}, and YbZn{sub 2}Sb{sub 2} were grown from melts of nominal composition AZn{sub 5}Sb{sub 5} (A = Ca,Eu,Yb) with the excess melt being removed at 1073 K. The electrical transport properties are consistent with those previously reported for polycrystalline samples. This confirms that the p-type carrier concentrations ranging from 2 x 10{sup 19} cm{sup -3} to -1 x 10{sup 20} cm{sup -3} are intrinsic to these materials. Also consistent with transport in polycrystalline materials, the carrier mobility is found to be lowest in CaZn{sub 2}Sb{sub 2}, suggesting the trends in mobility and thermoelectric efficiency within these compounds are inherent to the material systems and not due to inhomogeneity or impurities in polycrystalline samples. These results suggest CaZn{sub 2}Sb{sub 2} has the strongest coupling between the doping/defects and the electronic framework. Magnetization measurements reveal an antiferromagnetic transition near 13 K in EuZn{sub 2}Sb{sub 2}, and the observed magnetic anisotropy indicates the spins align parallel and anti-parallel to c in the trigonal lattice. Powder neutron diffraction on polycrystalline samples of CaZn{sub 2}Sb{sub 2} and YbZn{sub 2}Sb{sub 2} reveals smooth lattice expansion to 1000 K, with c expanding faster than a. The Debye temperatures calculated from specific heat capacity data and the isotropic displacement parameters are found to correlate with the carrier mobility, with the CaZn{sub 2}Sb{sub 2} displaying the largest Debye temperature and smallest mobility.

May, Andrew F [ORNL; McGuire, Michael A [ORNL; Ma, Jie [ORNL; Delaire, Olivier A [ORNL; Huq, Ashfia [ORNL; Custelcean, Radu [ORNL

2012-01-01

52

Optical temperature sensor through infrared excited blue upconversion emission in Tm3 +/Yb3 + codoped Y2O3  

NASA Astrophysics Data System (ADS)

An analysis of the intense blue upconversion emission at 476 and 488 nm in Tm3 +/Yb3 + codoped Y2O3 under excitation power density of 86.7 W/cm2 available from a diode laser emitting at 976 nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 476 and 488 nm in this material was recorded in the temperature range from 303 to 753 K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.0035 K- 1. The results imply that Tm3 +/Yb3 + codoped Y2O3 is a potential candidate for the optical temperature sensor.

Li, Dongyu; Wang, Yuxiao; Zhang, Xueru; Yang, Kun; Liu, Lu; Song, Yinglin

2012-04-01

53

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

54

Vacuum ultraviolet and near-infrared excited luminescence properties of Ca3(PO4)2:RE3+, Na+ (RE=Tb, Yb, Er, Tm, and Ho)  

NASA Astrophysics Data System (ADS)

Tb3+, Yb3+, Tm3+, Er3+, and Ho3+ doped Ca3(PO4)2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb3+ content is comparable with that of the commercial Zn2SiO4:Mn2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb3+, Tm3+, Er3+, and Ho3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb3+-Ho3+, Yb3+-Er3+, and Yb3+-Tm3+ in Ca3(PO4)2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb3+-Tm3+-Er3+-Ho3+ in Ca3(PO4)2, in which the cross-relaxation process between Er3+ and Tm3+, producing the 1D2-3F4 transition of Tm3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams.

Zhang, Jia; Wang, Yuhua; Guo, Linna; Zhang, Feng; Wen, Yan; Liu, Bitao; Huang, Yan

2011-08-01

55

Synthesis and crystal structures of RERhIn ( RE=Sm, Tb, Ho, Er, Tm, Yb, Lu)  

Microsoft Academic Search

The intermetallic rare earth metal compounds RERhIn (RE=Sm, Tb, Ho, Er, Tm, Yb and Lu) were synthesized from the elements by arc-melting, by reactions in sealed niobium tubes in a high-frequency furnace, or by induction melting in glassy carbon crucibles. All compounds were investigated by X-ray powder diffraction and the structures have been refined on the basis of single-crystal diffractometer

Mary'ana Lukachuk; Vasyl’ I. Zaremba; Rainer Pöttgen

2003-01-01

56

Pump-power-controlled luminescence switching in Yb3+\\/Tm3+ codoped water-free low silica calcium aluminosilicate glasses  

Microsoft Academic Search

Intense infrared-to-visible upconversion emissions in Tm3+\\/Yb3+ codoped water-free low silica calcium aluminosilicate glasses have been obtained under excitation at 976 nm. The results showed that as the pump power\\/intensity is increased, a reduction of up to one order of magnitude at the 800\\/480 nm emitted intensity ratio is observed; characterizing what can be denominated as luminescent switching. The physical origin

C. Jacinto; M. V. D. Vermelho; E. A. Gouveia; M. T. de Araujo; P. T. Udo; N. G. C. Astrath; M. L. Baesso

2007-01-01

57

Pump-power-controlled luminescence switching in Yb3+?Tm3+ codoped water-free low silica calcium aluminosilicate glasses  

Microsoft Academic Search

Intense infrared-to-visible upconversion emissions in Tm3+?Yb3+ codoped water-free low silica calcium aluminosilicate glasses have been obtained under excitation at 976 nm. The results showed that as the pump power\\/intensity is increased, a reduction of up to one order of magnitude at the 800?480 nm emitted intensity ratio is observed; characterizing what can be denominated as luminescent switching. The physical origin

C. Jacinto; M. V. D. Vermelho; E. A. Gouveia; M. T. de Araujo; P. T. Udo; N. G. C. Astrath; M. L. Baesso

2007-01-01

58

Magnetic, thermodynamic, and electrical transport properties of ternary equiatomic ytterbium compounds YbTM (T=transition metal, M=Sn and Bi)  

NASA Astrophysics Data System (ADS)

Physical behavior of several YbTM intermetallics has been studied by means of x-ray powder diffraction, magnetization, dc magnetic susceptibility, heat capacity, and electrical resistivity measurements. The compounds YbTBi with T=Cu, Ag, Au and YbTSn with T=Ag, Au, Zn were shown to be nonmagnetic due to the presence of divalent ytterbium ions. The bismuthide YbPdBi as well as the stannides YbRhSn and YbPtSn were found to exhibit localized magnetism of almost trivalent Yb ions. The electrical behavior of these three phases is characteristic of dense Kondo systems, and their low-temperature specific heat data indicate a possible heavy fermion ground state.

Kaczorowski, D.; Leithe-Jasper, A.; Rogl, P.; Flandorfer, H.; Cichorek, T.; Pietri, R.; Andraka, B.

1999-07-01

59

WHITE UPCONVERSION LUMINESCENCE FROM (Yb3+/Tm3+/Ho3+) TRIDOPED GdF3 NANORODS AFTER HEAT TREATMENT  

NASA Astrophysics Data System (ADS)

A series of Ho3+/Yb3+/Tm3+ tridoped GdF3 nanorods with different dopant concentrations were synthesized by a hydrothermal method. Transmission electron microscope (TEM) images indicate that the length and diameter of the nanorods is about 90 nm and 31 nm, respectively on average. No bright white upconversion light was observed from the samples with different Yb3+, Ho3+ or Tm3+ concentrations. Unexpectedly, the emission color coordinates of the samples after heat treatment move toward the central white region of the chromaticity diagram, and among these samples, the color coordinate (0.349, 0.329) of GdF3:15% Yb3+, 0.1% Ho3+, 0.8% Tm3+ is the most close to the standard white light (0.333, 0.333). This is unlike previous reports in which white light was achieved via tuning dopant concentration or excitation power. The reasons for the above phenomenon are presented by means of FT-IR spectra and the energy level diagram of dopants.

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

2012-09-01

60

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

61

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

NASA Astrophysics Data System (ADS)

Pump and thermally induced color tunabilities were demonstrated in Yb3+/Tm3+ codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 ?m. 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/cm2 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 (Yb3+-->Tm3+ energy-transfer processes, easy saturations of the Yb3+ and Tm3+ 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.

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.

2010-07-01

62

Upconversion luminescence enhancement in Yb3+/Tm3+-codoped Lu2O3 nanocrystals induced by doping with Li+ ions.  

PubMed

Lutetium oxide (Lu2O3) nanocrystals doped with 2%Yb3+, 0.5%Tm3+, and various doping concentrations of Li+ (0, 3, 5, 7, 10, 12, and 15 mol%) were prepared by the sol-gel method. The dependence on different doping concentrations of Li+ ions of the structure, morphology, and the upconversion emission intensity of the Lu2O3:2%Yb3+, 0.5%Tm3+ nanocrystals was investigated. The obtained Lu2O3 nanocrystals were systematically characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), Fourier transformed infrared (FT-IR) spectra, Raman spectra, and upconversion spectra measurements. It was found that all the nanocrystals can be readily indexed to pure cubic phase of Lu2O3, indicating good crystallinity. The experimental results show that Li+ doping in Lu2O3:2%Yb3+, 0.5%Tm3+ nanocrystals can greatly enhance the upconversion emission intensity. The strong blue (490 nm) and the weak red (653 nm) emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4 --> 3H6 and 1G4 --> 3F4 transitions of Tm3+ ions, respectively. An simple analysis based on steady-state rate equations and a power-dependent study both indicate that the 1G4 levels can be populated by three-step energy transfer (ET) processes. The enhancement of the upconversion luminescence was suggested to be the consequence of the modification of the local field symmetry around the Tm3+ ion, reduced number of OH- groups, and the enlarged nanocrystal size induced by the Li+ ions. PMID:22413316

Li, Li; Xiantao, Wei; Xueqin, Cao; Kaimo, Deng; Qihong, Chen; Yonghu, Chen; Changxin, Guo; Min, Yin

2011-11-01

63

Multicolor upconversion luminescence in monodispersed Ba2LaF7:Ln3+ (Ln=Yb/Er and Yb/Tm) nanocrystals  

NASA Astrophysics Data System (ADS)

Lanthanide-doped Ba2LaF7 nanocrystals have been successfully synthesized via a modified liquid-solid-solution process. The yielded nanocrystals are determined to be pure cubic Ba2LaF7 phase and consist of nearly square-shaped nanoparticles with an average 14 nm in size. The Yb3+/Er3+ (Tm3+) co-doped Ba2LaF7 nanocrystals emit bright multicolor upconversion luminescence following the excitation of 980 nm laser diode. Proposed mechanisms for the emission were analyzed based on the emission spectra and their dependence on pumping power, as well as corresponding energy level diagram.

Li, Wenbin; Tan, Congbing; Zhang, Yutao

2013-02-01

64

Effects of RE2O3 (RE = Tm, Sc, Yb) addition on the superconducting properties of ErBa2Cu3Oy  

NASA Astrophysics Data System (ADS)

We investigated the effects of added Tm2O3, Sc2O3, and Yb2O3 on the superconducting properties of sintered Er123 samples. Tm2O3 addition caused the least Tc degradation, exhibiting a Tc above 90 K even for 17 vol% addition. Samples with added Sc2O3 maintained a Tc at above 90 K up to an addition of 7.2 vol%, while Yb2O3-containing samples showed a monotonic decrease in Tc with increased vol% of added Yb2O3. Tm2O3-containing samples exhibited a slight increase in Jc(0.1 T)/Jc(0) and had constant Jc values even for 17 vol% addition. XRD and SEM results indicate that the Tm2O3 is very stable in the superconducting matrix.

Kita, R.; Hosoya, N.; Otawa, N.; Kawabata, S.; Nakamura, T.; Miura, O.; Mukaida, M.; Yamada, K.; Ichinose, A.; Matsumoto, K.; Horii, M. S.; Yoshida, Y.

2009-10-01

65

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

NASA Astrophysics Data System (ADS)

Eu2+-Yb3+ 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 Eu2+ indicated the partition of Eu2+ into FAP nanocrystals in glass ceramic. NIR emission due to the transition 2F?2F of Yb3+ ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu2+ to Yb3+, which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu2+-Yb3+ co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells.

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

2013-10-01

66

Multicolor up conversion emission and color tunability in Yb3+/Tm3+/Ho3+ triply doped heavy metal oxide glasses  

NASA Astrophysics Data System (ADS)

Multicolor and white light emissions have been achieved in Yb3+, Tm3+ and Ho3+ 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 TeO2-GeO2-Bi2O3-K2O 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% Yb2O3, 0.6 wt% Tm2O3 and 0.1 wt% Ho2O3) 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 Tm3+ ions and a two-photon green and red up conversions of Ho3+ 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

67

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

68

Investigations into the Eu-Eu2O3, the Eu-Pt-Eu2O3, the Sm-Sm2O3, and the Yb-Yb2O3 systems  

Microsoft Academic Search

The binary system Eu-Eu2O3 has been examined in detail over the composition range EuO to Eu2O3 at 1500°C. Only three oxide phases were found: EuO, Eu3O4, and Eu2O3. Both EuO and Eu3O4 exhibit very narrow composition limits, while the monoclinic sesquioxide is stable over the composition range EuO1.45 to EuO1.50 at 1500°C. The melting points found for the three phases

R. G. Bedford; E. Catalano

1971-01-01

69

Manifestation of up-conversion in Yb3+/Tm3+ doped Li2O-Y2O3-SiO2 glass system  

NASA Astrophysics Data System (ADS)

In this study, we have investigated the principal role of Y2O3 on the emission features of Tm3+ ion and up-conversion phenomenon in Tm3+ and Yb3+ co-doped Li2O-Y2O3-SiO2 glass system. The concentration of Y2O3 is varied from 0 to 5 mol% while that of Yb3+ and Tm3+ is fixed. When the glasses are doped with Tm3+ ions, the intense blue and red emissions were observed, whereas Yb3+ doped glasses exhibited NIR emission at about 980 nm. When the glasses are co-doped with Tm3+ and Yb3+ ions and excited at 900 nm, the blue and red emission lines were observed to be reinforced and strengthened with increase in the concentration of Y2O3. The IR emission band detected at about 1.8 ?m due to 3F4 ? 3H6 transition of Tm3+ ions is also observed to be strengthened due to co-doping. The reasons for enhancement in the intensity of various emission bands due to co-doping have been identified and discussed with the help of rate equations for various emission transitions.

Ramesh Babu, N. Ch.; Srinivasa Rao, Ch.; Brik, M. G.; Naga Raju, G.; Kityk, I. V.; Veeraiah, N.

2013-03-01

70

Pump-power-controlled luminescence switching in Yb3+/Tm3+ codoped water-free low silica calcium aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

Intense infrared-to-visible upconversion emissions in Tm3+/Yb3+ codoped water-free low silica calcium aluminosilicate glasses have been obtained under excitation at 976 nm. The results showed that as the pump power/intensity is increased, a reduction of up to one order of magnitude at the 800/480 nm emitted intensity ratio is observed; characterizing what can be denominated as luminescent switching. The physical origin of this switching is discussed and explained in terms of the tailoring of luminescent switchers to operate in a large range of pump powers, what could be used in the development of sensors and networks for optical processing and optical communications.

Jacinto, C.; Vermelho, M. V. D.; Gouveia, E. A.; de Araujo, M. T.; Udo, P. T.; Astrath, N. G. C.; Baesso, M. L.

2007-08-01

71

Colloidal synthesis and blue based multicolor upconversion emissions of size and composition controlled monodisperse hexagonal NaYF4 : Yb,Tm nanocrystals  

NASA Astrophysics Data System (ADS)

Monodisperse ?-NaYF4 : Yb,Tm nanocrystals with controlled size (25-150 nm), shape (sphere, hexagonal prism, and hexagonal plate), and composition (Yb: 20-40%, Tm: 0.2-5%) were synthesized from the thermolysis of metal trifluoroacetates in hot surfactant solutions. The upconversion (UC) of near-infrared light (980 nm) to ultra-violet (360 nm), blue (450 and 475 nm), red (650 and 695 nm) and infrared (800 nm) light in the ?-NaYF4 : Yb,Tm nanocrystals has been studied by UC spectroscopy. Both the total intensity of UC emissions and the relative intensities of emissions at different wavelengths have shown a strong dependence on different particle sizes and different Tm3+ and Yb3+ concentrations. As a result, different overall output colors of UC emissions can be achieved by altering sizes and Yb3+/Tm3+ doping concentrations of the ?-NaYF4 : Yb,Tm nanocrystals. The intensity-power curves of a series of samples have proved that emissions at 360 and 450 nm can be ascribed to four-photon process (1D2 to 3H6 and 1D2 to 3H4, respectively), while emissions at 475 and 650 nm are three-photon processes (1G4 to 3H6 and 1G4 to 3H4, respectively) and emissions at 695 and 800 nm are two-photon ones (3F2 to 3H6 and 3F4 to 3H6, respectively). A UC saturation effect would occur under a certain excitation intensity of the 980 nm CW diode laser for the as-obtained ?-NaYF4 : Yb,Tm nanocrystals, leading to the decrease of the slopes of the I-P curves. The results of our study also revealed that the successive transfer model instead of the cooperative sensitization model can be applied to explain the UC behaviors of the ?-NaYF4 : Yb,Tm nanocrystals. Further, an unexpected stronger emissions of four-photon process at 360 and 450 nm for ~50 nm ?-NaYF4 : Yb,Tm nanocrystals than those for the bigger (~150 nm) nanocrystals was observed and explained in terms of the effects of crystallite size, surface-to-volume ratio and homogeneity of the doping cations.Monodisperse ?-NaYF4 : Yb,Tm nanocrystals with controlled size (25-150 nm), shape (sphere, hexagonal prism, and hexagonal plate), and composition (Yb: 20-40%, Tm: 0.2-5%) were synthesized from the thermolysis of metal trifluoroacetates in hot surfactant solutions. The upconversion (UC) of near-infrared light (980 nm) to ultra-violet (360 nm), blue (450 and 475 nm), red (650 and 695 nm) and infrared (800 nm) light in the ?-NaYF4 : Yb,Tm nanocrystals has been studied by UC spectroscopy. Both the total intensity of UC emissions and the relative intensities of emissions at different wavelengths have shown a strong dependence on different particle sizes and different Tm3+ and Yb3+ concentrations. As a result, different overall output colors of UC emissions can be achieved by altering sizes and Yb3+/Tm3+ doping concentrations of the ?-NaYF4 : Yb,Tm nanocrystals. The intensity-power curves of a series of samples have proved that emissions at 360 and 450 nm can be ascribed to four-photon process (1D2 to 3H6 and 1D2 to 3H4, respectively), while emissions at 475 and 650 nm are three-photon processes (1G4 to 3H6 and 1G4 to 3H4, respectively) and emissions at 695 and 800 nm are two-photon ones (3F2 to 3H6 and 3F4 to 3H6, respectively). A UC saturation effect would occur under a certain excitation intensity of the 980 nm CW diode laser for the as-obtained ?-NaYF4 : Yb,Tm nanocrystals, leading to the decrease of the slopes of the I-P curves. The results of our study also revealed that the successive transfer model instead of the cooperative sensitization model can be applied to explain the UC behaviors of the ?-NaYF4 : Yb,Tm nanocrystals. Further, an unexpected stronger emissions of four-photon process at 360 and 450 nm for ~50 nm ?-NaYF4 : Yb,Tm nanocrystals than those for the bigger (~150 nm) nanocrystals was observed and explained in terms of the effects of crystallite size, surface-to-volume ratio and homogeneity of the doping cations. Electronic supplementary information (ESI) available: More TEM images and UC results of the ?-NaYF4 : Yb,Tm nanocrystals. See DOI: 10.1039/b9nr00397e

Yin, Anxiang; Zhang, Yawen; Sun, Lingdong; Yan, Chunhua

2010-06-01

72

NIR-to-NIR two-photon excited CaF2:Tm3+,Yb3+ nanoparticles: multifunctional nanoprobes for highly penetrating fluorescence bio-imaging.  

PubMed

In this study, we report on the remarkable two-photon excited fluorescence efficiency in the "biological window" of CaF(2):Tm(3+),Yb(3+) nanoparticles. On the basis of the strong Tm(3+) ion emission (at around 800 nm), tissue penetration depths as large as 2 mm have been demonstrated, which are more than 4 times those achievable based on the visible emissions in comparable CaF(2):Er(3+),Yb(3+) nanoparticles. The outstanding penetration depth, together with the fluorescence thermal sensitivity demonstrated here, makes CaF(2):Tm(3+),Yb(3+) nanoparticles ideal candidates as multifunctional nanoprobes for high contrast and highly penetrating in vivo fluorescence imaging applications. PMID:21957870

Dong, Ning-Ning; Pedroni, Marco; Piccinelli, Fabio; Conti, Giamaica; Sbarbati, Andrea; Ramírez-Hernández, Juan Enrique; Maestro, Laura Martínez; Iglesias-de la Cruz, Maria Carmen; Sanz-Rodriguez, Francisco; Juarranz, Angeles; Chen, Feng; Vetrone, Fiorenzo; Capobianco, John A; Solé, José García; Bettinelli, Marco; Jaque, Daniel; Speghini, Adolfo

2011-10-06

73

Controlled synthesis of NaYF4 nanoparticles and upconversion properties of NaYF4:Yb, Er (Tm)/FC transparent nanocomposite thin films.  

PubMed

Monodisperse oleic acid stabilized pure NaYF(4) nanoparticles with controlled size and shape have been successfully synthesized by changing the initial reaction temperature. Transparent nanocomposite thin films consisting of NaYF(4):Yb, Er (Tm) upconverting nanoparticles (UCNPs) and fluorocarbon resin (FC) are deposited on the slide glass by dip-coating method. The results show that these nanocomposite thin films exhibit intense green and blue upconversion photoluminescence under 980 nm laser excitation and higher transparency than blank substrate. The NaYF(4):Yb,Er (Tm) nanoparticles and NaYF(4):Yb,Er (Tm)/FC nanocomposite thin films have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), SEM/back-scattered electron (BSE), atomic force microscopy (AFM), UV-Vis spectrophotometer (UVPC), and photoluminescence (PL) spectra. These nanocomposite thin films can be potentially used in solar cells field. PMID:22444484

Huang, Wenjuan; Lu, Chunhua; Jiang, Chenfei; Wang, Wei; Song, Jianbin; Ni, Yaru; Xu, Zhongzi

2012-03-06

74

Magnetic properties of RT2Al20 (R = Gd, Eu and Yb, T = Ti, V and Cr)  

NASA Astrophysics Data System (ADS)

Isostructural RT2Al20 series of compounds contain less than 5 at. % of rare earth ions. Thermodynamic and transport measurements were performed on solution-grown, single crystals: both R = Gd and Eu series manifest clear local moment behavior with magnetic ordering below 10 K. These low transition temperatures are consistent with the dilute nature of the rare earth ions. Unlike the RT2Zn20 series, we have not found enhanced magnetic order or near-Stoner like behavior for any member of the RT2Al20 family of compounds. The R = Yb members, however, all manifest weak Pauli paramagnetism, consistent with a divalent state for the Yb ions.

Frederick, J.; Jia, Shuang; Bud'Ko, S. L.; Canfield, P. C.

2008-03-01

75

980 nm laser-diode-excited intense blue upconversion in Tm3+/Yb3+-codoped gallate-bismuth-lead glasses  

NASA Astrophysics Data System (ADS)

Intense blue-upconversion in Tm3+/Yb3+-codoped gallate-bismuth-lead glasses has been achieved under an excitation from a commercially available 980 nm laser diode. Energy transfer processes and excited-state absorption account for the population of the 1G4 emitting level of the Tm3+. Although the addition of GeO2 has enhanced the glass thermal stability, the phonon mode associated with vibration of GeO2 has almost no influence on the blue-upconversion intensity and the radiative lifetime of 3H4 level. The dependence of the phonon energy of the host on contributions from multiphonon decay on the fluorescence has been discussed. Significant enhancement of the blue-upconversion has also been observed in gallate-bismuth-lead glasses with the incorporation of PbF2 content.

Zhang, Q. Y.; Li, T.; Jiang, Z. H.; Ji, X. H.; Buddhudu, S.

2005-10-01

76

Gain improvement by internal laser cavity in Tm(3+)Yb(3+)-co-doped tellurite fiber amplifier pumped by 980-nm laser.  

PubMed

S-band Tm(3+)/Yb(3+) co-doped tellurite fiber amplifier pumped by a 980 nm laser diode is proposed and modeled taking into consideration of the energy transfer process from Yb(3+) to Tm(3+) and the laser cavity inside a co-doped fiber amplifier. S-band spectral gains for the co-doped fiber amplifiers are investigated. The results show that considerable gain improvement can be achieved by constructing 1050nm laser cavity inside the amplifier. PMID:19529231

Chang, Jun; Wang, Qingpu; Peng, Gangding; Zhang, Xingyu; Liu, Zejin; Ding, Shuanghong; Liu, Zhaojun; Zhang, Sasa; Wang, Gongtang

2006-09-18

77

Intense ultraviolet and blue upconversion emissions in Yb3+-Tm3+ codoped stoichiometric Y7O6F9 powder  

NASA Astrophysics Data System (ADS)

Stoichiometric Y7O6F9 powder codoped with Yb3+-Tm3+ was synthesized via co-precipitation and subsequent calcining route. The results of X-ray diffraction and transmission electron microscopy reveal that when the calcining temperature is beyond 800 °C, orthorhombic YF3 nanoparticles can be completely oxidized into orthorhombic Y7O6F9 powder. Under the excitation of a 980 nm laser, Y7O6F9 powder exhibits multicolor UC emission in regions spanning the UV to the NIR. In addition, the upconversion emission intensities of YF3, Y7O6F9 and Y2O3 powders were compared under the same dopant condition (Yb/Tm=5/0.5 mol%). The low phonon energy revealed by Raman spectra helped to understand the high efficient upconversion emission of Y7O6F9 and the main phonon vibration of Y7O6F9 lies at 472 cm-1, which is far lower that of Y2O3 (at 708 cm-1). Our results indicate that orthorhombic rare earth ions doped Y7O6F9 is an efficient matrix for UV and blue UC emission, and has potential applications in color displays, anti-counterfeiting and multicolor fluorescent labels.

Ma, Mo; Xu, Changfu; Yang, Liwen; Ren, Guozhong; Lin, Jianguo; Yang, Qibin

2011-09-01

78

Hall and transverse even effects in the vicinity of a quantum critical point in Tm1 - x Yb x B12  

NASA Astrophysics Data System (ADS)

The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm1 - x Yb x B12 solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x c ? 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbium substitution in the range x > x c and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R H( T) for the Tm1 - x Yb x B12 compounds, in contrast to the invariable behavior R H( T) ? const found for TmB12. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x ? 0.5 with activation energies E g / k B ? 200 K and E a/ k B = 55-75 K, and the sign inversion of R H( T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm1 - x Yb x B12 solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained allow concluding that the emergence of Yb-Yb dimers in the Tm1 - x Yb x B12 cage-glass matrix is the origin of the metal-insulator transition observed in the achetypal strongly correlated electron system of YbB12.

Sluchanko, N. E.; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Anisimov, M. A.; Levchenko, A. V.; Filipov, V. B.; Shitsevalova, N. Yu.

2012-09-01

79

Hall and transverse even effects in the vicinity of a quantum critical point in Tm{sub 1-x}Yb{sub x}B{sub 12}  

SciTech Connect

The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x{sub c} Almost-Equal-To 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbium substitution in the range x > x{sub c} and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R{sub H}(T) for the Tm{sup 1-x}Yb{sub x}B{sub 12} compounds, in contrast to the invariable behavior R{sub H}(T) Almost-Equal-To const found for TmB{sub 12}. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x {>=} 0.5 with activation energies E{sub g}/k{sub B} Almost-Equal-To 200 K and E{sub a}/k{sub B} 55-75 K, and the sign inversion of R{sub H}(T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained allow concluding that the emergence of Yb-Yb dimers in the Tm{sub 1-x}Yb{sub x}B{sub 12} cage-glass matrix is the origin of the metal-insulator transition observed in the achetypal strongly correlated electron system of YbB{sub 12}.

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

2012-09-15

80

White up-conversion emission in Ho3+/Tm3+/Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals  

NASA Astrophysics Data System (ADS)

Ho3+/Tm3+/Yb3+ 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 Ho3+ ion and the blue emission is assigned to Tm3+ ion, whereas the red emission is the combination contribution of the Ho3+ and Tm3+ 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 Ho3+/0.2Tm3+/3Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals pumped by a single infrared laser diode source of 980 nm at 500 mW. The up-conversion luminescence mechanism of Yb3+ sensitize Ho3+ and Tm3+ ions and the energy transfer from Ho3+ to Tm3+ 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

Superconductivity and Phase Stability in the Heavy Rare Earth Quaternary Compounds RBa sub 2 Cu sub 3 O sub 7 (R = Ho, Er, Tm, Yb, Lu).  

National Technical Information Service (NTIS)

Phase stabiliy and superconducting properties of heavy rare earth compounds RBa sub 2 Cu sub 3 O sub 7 (R = Ho, Er, Tm, Yb, Lu) were studied and found to be unstable above 950 deg C. Transition temperatures depend heavily on starting materials, thermal hi...

H. C. Ku H. D. Yang R. W. McCallum M. A. Noack P. Klavins

1987-01-01

82

Features of the local structure of rare-earth dodecaborides RB12 (R = Ho, Er, Tm, Yb, Lu)  

NASA Astrophysics Data System (ADS)

The parameters of the local crystal structure of dodecaborides RB12 (R = Ho, Er, Tm, Yb, Lu) have been determined by extended X-ray absorption fine structure (EXAFS) spectroscopy. It has been shown that the vibrations of the rare-earth ion with respect to the boron cage are well described in the harmonic approximation. At the same time, the displacement of rare-earth ions from equilibrium positions of the crystal structure should be taken into account to determine the length of the R-B bond. The analysis of EXAFS spectra has revealed the displacement of 1-6% of rare-earth ions by about 0.2-0.3 Å in all compounds under investigation; this displacement at low temperatures results in the formation of a cage glass phase.

Menushenkov, A. P.; Yaroslavtsev, A. A.; Zaluzhnyy, I. A.; Kuznetsov, A. V.; Chernikov, R. V.; Shitsevalova, N. Yu.; Filippov, V. B.

2013-10-01

83

Investigation on luminescence properties of Er3+-Yb3+-Tm3+ co-doped Gd2O3 hollow microspheres  

NASA Astrophysics Data System (ADS)

The Gd2O3 hollow microspheres have been successfully fabricated via carbonaceous polysaccharide microspheres as templates and urea as a precipitating agent, which involved the deposition of an inorganic coating on the surface of carbon microsphere, followed by heat treated 800°C for 4h. The obtained high uniform Gd2O3 microspheres with a spherical shape and hollow structure are uniform in size and distribution. The possible mechanism of evolution from glucose to carbonaceous polysaccharide microspheres and the chemical reaction of each step to form the final hollow spheres are proposed. The rare earth ion Ln3+ doped Gd2O3 (Ln = Er, Yb and Tm) hollow microspheres show bright up-conversion luminescence with different colors coming from different activator ions under ultraviolet or 980 nm light excitation, which may open new possibilities to synthesize other hollow spherical materials and extend their applications.

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

2011-06-01

84

Investigation on upconversion luminescence properties of Gd2O3: Ho3+/Yb3+/Tm3+ nanotubes  

NASA Astrophysics Data System (ADS)

Lanthanide doped oxides nano materials have novel optical, physical and structural properties. Cubic Ho3+-Yb3+-Tm3+ co-doped Gd2O3 nanotubes are synthetize by a simple wet-chemical route at low temperature and ambient pressure followed by subsequent annealing heat treatment in muffle furnace. Nanotubes are formed by adjusting the pH value of reacting solution. The introduction of Yb3+ leads to strong visible upconversion luminescence and change the intensity ratio of the green, blue and red luminescence. In trichromatic laser display, research of how to enhance blue light is in the bottleneck period. In the experiment, the blue emission has been successfully improved. In certain doping ratio, distinct enhancement of blue emission and obvious degradation of green light have been observed, which is discussed in detail. X-Ray powder diffraction (XRD), scanning electron microscope (SEM) and upconversion (UC) emission spectra are used to characterize the sample. Strong and adjusted upconversion luminescence determine that the nano material is a potential candidate for applications of biological probe, color displays, lighting and photonics.

Ye, Fei; Fang, Yu; Liu, Xiao-bo; Xu, Fang; Song, Ying-lin

2013-09-01

85

Hydrothermal synthesis and upconversion luminescence properties of ?-NaGdF4:Yb3+/Tm3+ and ?-NaGdF4:Yb3+/Ho3+ submicron crystals with regular morphologies.  

PubMed

Single phase ?-NaGdF(4):Yb(3+)/Tm(3+) and ?-NaGdF(4):Yb(3+)/Ho(3+) submicron crystals with various morphologies including hexagonal prisms, spindles, and spheres were synthesized via the one-step hydrothermal method by controlling the pH values and sort of chelators (EDTA and citric acid). The prepared products showed intense up-converted luminescence (UCL) pumped by infrared laser at 980 nm. The hexagonal prisms that meaning high degree crystallinity demonstrated strong UCL in comparison with other morphologies such as spindles and spheres. In ?-NaGdF(4):Yb(3+)/Tm(3+), UCL not only appeared transitions from (1)G(4), (1)D(2), and (1)I(6) states to the lower lying states of Tm(3+), but also (6)P(J)?(8)S(7/2) transition (310 nm) of Gd(3+). These UCL were responsible for three, five, and six photons processes determined by pump power dependence of UCL intensities. The observation of UCL of Gd(3+) implied occurrence of energy transfer from Tm(3+):(1)I(6) to Gd(3+):(6)P(J). PMID:23141700

Li, Jing; Hao, Zhendong; Zhang, Xia; Luo, Yongshi; Zhao, Jihong; Lü, Shaozhe; Cao, Jian; Zhang, Jiahua

2012-10-22

86

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

87

Bright white upconversion emission from Yb(3+), Er(3+), and Tm(3+)-codoped Gd(2)O(3) nanotubes.  

PubMed

Yb(3+), Er(3+), and Tm(3+)-codoped Gd(2)O(3) nanotubes were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 degrees C. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), upconversion (UC) emission spectra, and kinetic decay were used to characterize the samples. Bright white UC luminescence in the nanotubes was observed under diode laser excitation of 980 nm. The white light consists of the blue ((1)G(4)-->(3)H(6) of Tm(3+)), green ((2)H(11/2)/(4)S(3/2)-->(4)I(15/2) of Er(3+)), and red ((4)F(9/2)-->(4)I(15/2) of Er(3+)) UC emissions. As the excitation power density changed in the range of 20-200 W cm(-2), the calculated CIE color coordinates shift only slightly and fall well within the white region. This material may be a potential candidate for applications of color displays, lighting and photonics. PMID:20544112

Zheng, Kezhi; Zhang, Daisheng; Zhao, Dan; Liu, Ning; Shi, Feng; Qin, Weiping

2010-06-14

88

[Color-tunable nano-material alpha-NaYF4 : Yb, Er, Tm prepared by microemulsion-hydrothermal method].  

PubMed

NaYF4 : Yb3+, Er3+, Tm3+ nanoparticles were prepared by microemulsion-hydrothermal method. Crystal phase, morphology and structure of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The luminescence properties were studied by up-conversional fluorescence spectroscopy. The XRD patterns of as-prepared samples were in agreement with the PDF # 77-2042 of cubic NaYF4. SEM images of the particles showed that the samples were cotton-like spherical in shape and which were assembled by smaller nano-particles. The average size was 120 nm, while the shape was regular and the particle size was homogeneous. Under the excitation of 980 nm, the as-prepared particles could emit blue (438 and 486 nm), green (523 and 539 nm) and red (650 nm) light simultaneously. It can be seen from the color coordinates figure (CIE) that when doping concentration ratio of Tm3+ and E3+ increased from 0 to 2, the whole emitting light color of samples movedto green region. While the ratio was 1 : 1, pseudo white light was obtained. As the ratio changed from 2 to 7, the luminous color was moved to red region. PMID:24159845

Long, Dan-Dan; Zhang, Qing-Xia; Wang, Yu; Zhang, Fan; Wang, Yan-Fei; Zhou, Xin; Qi, Xiao-Hua; Zhang, Heng; Yan, Jing-Hui; Zou, Ming-Qiang

2013-08-01

89

Photoluminescence study of Y2O3:Er3+-Eu3+-Yb3+ phosphor for lighting and sensing applications  

NASA Astrophysics Data System (ADS)

The Er3+, Eu3+, and Yb3+ codoped Y2O3 phosphors have been synthesized by combustion synthesis process. For the structural information, the XRD analysis of the developed phosphor has been done. The frequency upconversion (UC) emissions in the codoped Y2O3 phosphor on excitation with 980 nm diode laser in the visible region have been performed and explained on the basis of excited state absorption and energy transfer process. The mechanism responsible in UC emissions was observed to involve two photon absorption and efficiency of the UC luminescence is significantly enhanced by introducing the Yb3+ ions. The tunability in colour of emitted radiation has been visualized by chromaticity diagram on increasing power of excitation source. The temperature sensing behaviour of developed phosphor material has been investigated using fluorescence intensity ratio technique.

Kumar Rai, Vineet; Pandey, Anurag; Dey, Riya

2013-02-01

90

Spectroscopic properties of Y3TaO7 powders activated with Eu, Er and co-activated with Yb  

NASA Astrophysics Data System (ADS)

A new synthesis method of Y3TaO7 is reported. Pure phase powders were prepared by modified Pechini technique. Precursors obtained through that route were heated at the temperature about 1000°C with or without use of Li2SO4 flux. That implicates in different morphology of specimens and also their spectroscopic properties. Eu ions were used as a spectroscopic probe to prove inhomogeneous broadening of excitation and emission spectra. Samples with Er and Yb doping are also presented. Photoluminescence and up-conversion emissions, under 378 nm and 980 nm excitation respectively, strongly depend on the method of powders synthesis.

Walasek, Adam; Zych, Eugeniusz; Liqiong, An; Zhang, Jian; Wang, Shiwei

2007-08-01

91

Sensitized deep-ultraviolet up-conversion emissions of Gd3+ via Tm3+ and Yb3+ in hexagonal NaYF4 nanorods  

NASA Astrophysics Data System (ADS)

Deep-ultraviolet (UV) up-conversion (UC) emissions in the region of 270˜330 nm of Gd3+ under the excitation of a 980 nm laser diode in hexagonal Yb3+-Tm3+-Gd3+ triply doped NaYF4 nanorods synthesized using a hydrothermal method are reported. Spectral analyses indicate that the UV UC emissions originate from highly efficient energy transfer from Yb3+ to Tm3+, then to Gd3+ions, and the intensity of the emission as well as the ratios of the emission peaks are strongly dependent on the doping concentrations and pump power. The materials are envisioned to have potential applications in anti-counterfeiting, optical and magnetic dual modal nanoprobes for biomedicine, solution-based scintillator materials and UV compact solid-state lasers.

Zhang, Y. Y.; Yang, L. W.; Xu, C. F.; Zhong, J. X.; Sun, C. Q.

2010-02-01

92

Fractionation of rare earth elements in refractory inclusions from the Ningqiang meteorite: Origin of positive anomalies in Ce, Eu, and Yb  

NASA Astrophysics Data System (ADS)

Ion microprobe analyses of rare earth elements (REEs), Ba, and Hf were performed for various types of refractory inclusions including amoeboid olivine aggregates (AOAs) from the Ningqiang ungrouped carbonaceous chondrite to search for possible relationships between REE abundance patterns and bulk chemical compositions of the inclusions. Four types of CI-normalized REE patterns were recognized: (1) nearly flat (unfractionated) pattern with or without Eu (and Yb) anomalies (Groups I, III, or V), (2) depletions of ultrarefractory heavy REEs (HREEs) relative to light REEs (LREEs), and depletions of Eu and Yb ( Group II, but without depletion of Yb in some cases), (3) depletions of ultrarefractory HREEs with positive anomalies in Ce, (Eu), and Yb ( Modified Group II), and (4) nearly flat pattern with positive anomalies in Ce, (Eu), and Yb ( Modified Group I). No systematic correlation was found between bulk chemical compositions and REE patterns of the inclusions. This suggests that the observed REE fractionations occurred prior to condensation of major elements (e.g., Mg and Si) which defined bulk chemical compositions of the inclusions. It is remarkable that 7 out of 19 inclusions show positive anomalies in Ce, Yb, and in some cases, Eu as well (Modified Group I and Modified Group II), suggesting that such anomalies are rather common among inclusions in the Ningqiang and possibly in other primitive meteorites. Two possible mechanisms are considered for the formation of Modified Group II and Modified Group I patterns. In Model 1, Modified Group II is formed by a process similar to that produced Group II but removal of ultrarefractory dust occurred at slightly lower temperatures, where not only ultrarefractory HREEs but some fraction of LREEs had been condensed and removed from the system. Modified Group I may be explained by addition of an unfractionated component to the Modified Group II component, or alternatively, by partial removal of ultrarefractory dust from the system. In Model 2, Modified Group II is formed by later addition of Ce, (Eu), and Yb onto fine-grained dust or inclusions having HREE-depleted, Group II-like REE patterns. Similarly, Modified Group I is explained by later addition of Ce, (Eu), and Yb onto those with almost unfractionated REE patterns. The observed REE data show that both the degree of HREE-depletion (e.g., Er-depletion) and that of fractionation among HREEs (e.g., depletion in the Er/Gd ratio) for Modified Group II are very similar to those for Group II. Model 1 predicts almost complete removal of ultrarefractory HREEs from the system, resulting in much higher HREE-depletion for Modified Group II, which is not consistent with the present observations. Addition of an unfractionated component may explain moderate depletion of HREEs in Modified Group II, but it will diminish fractionation among HREEs, which is not consistent with the present observations. In contrast, Model 2 predicts no correlations between Ce-(Eu)-Yb-enrichment and HREE-depletion or between Ce-(Eu)-Yb-enrichment and fractionation among HREEs, consistent with the present observations. Hence, Model 2 seems more likely. If this is the case, at least two distinct regions with different REE characteristics are required for the formation of Modified Group II inclusions: one is a high temperature region where Group II-like (HREE-depleted) inclusions or their precursors are formed by condensation from a fractionated gas after removal of ultrarefractory dust, and another is a low temperature region enriched in Ce, Eu, and Yb in the gas phase. Abundant occurrence of positive Ce-(Eu)-Yb anomalies suggests that migration of solid materials from one region to another occurs rather frequently in the solar nebula. The most likely place satisfying such conditions for the formation of these inclusions may be the innermost part of the protoplanetary disk.

Hiyagon, H.; Yamakawa, A.; Ushikubo, T.; Lin, Y.; Kimura, M.

2011-06-01

93

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

94

Superconductivity and phase stability in the heavy rare earth quaternary compounds RBa2Cu3O7 (R = Ho, Er, Tm, Yb, Lu)  

NASA Astrophysics Data System (ADS)

Phase stability and superconducting properties of heavy rare earth compounds RBa sub 2 Cu sub 3 O sub 7 (R = Ho, Er, Tm, Yb, Lu) were studied and found to be unstable above 950 C. Transition temperatures depend heavily on starting materials, thermal history, oxygen content and the interpretation of the data. Magnetic rare earth ions have little effect on the transition temperature. However, these magnetic compounds should order magnetically, probably in the mK range.

Ku, H. C.; Yang, H. D.; McCallum, R. W.; Noack, M. A.; Klavins, P.; Shelton, R. N.; Moodenbaugh, A. R.

1987-04-01

95

Highly efficient upconversion emission and luminescence switching from Yb 3+\\/Tm 3+ co-doped water-free low silica calcium aluminosilicate glass  

Microsoft Academic Search

We present highly efficient 480 and 800nm upconversion emissions in Tm3+\\/Yb3+ co-doped water-free low silica calcium aluminosilicate glass under excitation at 976nm. As a result of this efficient upconversion process, a luminescent switching with the excitation intensity has been observed. The switching is explained and discussed using rate equations analysis and saturation effects. By means of fitting of the experimental

W. F. Silva; F. G. Rego-Filho; M. T. de Araujo; E. A. Gouveia; M. V. D. Vermelho; P. T. Udo; N. G. C. Astrath; M. L. Baesso; C. Jacinto

2008-01-01

96

Nuclear Quadrupole Coupling and Crystal-Field Effects in the Cubic Intermetallic Compounds ErAl3, TmAl3, and YbAl3  

Microsoft Academic Search

The presence of a large nuclear quadrupole coupling of the Al nucleus, as measured with NMR, in the cubic rare-earth aluminum intermetallic compounds beta-ErAl3, TmAl3, and YbAl3 indicates that the net charges at the rare-earth and aluminum sites differ by as much as 3 to 4 unit charges. Data on the magnetic susceptibility and this result have been used to

H. W. de Wijn; A. M. van Diepen; K. H. Buschow

1970-01-01

97

Comparison of ultraviolet upconversion luminescence between thin film and bulk of calcium fluoride co-doped with Yb3+/Tm3+ ions.  

PubMed

A calcium fluoride thin film co-doped with Yb3+/Tm3+ was deposited on Si substrates by the spin-coating method using trifluoroacetic acid as a fluorine source. The scanning electron microscopy (SEM) image of the sample showed that a thin film with some cracks was formed. After annealing, the cracks disappeared, and the film became thinner. The roughness of the thin film was about 150 nm, which was confirmed by atomic force microscopy (AFM). Moreover, the upconversion luminescence properties of the thin film after annealing were studied. Under infrared light excitation, strong ultraviolet (UV) upconversion luminescence of the thin film was observed. To compare the upconversion properties, Yb3+/Tm3+ co-doped calcium fluoride bulk material that has the same components with the thin film was also synthesized. Compared with the bulk material, the UV upconversion emission of thin film was more intense. The mechanism of UV upconversion was determined by analyzing the upconversion spectra. The decrease in the size of the CaF2 Yb3+/Tm3+ particles to the nano-scale in the thin film contributed to the enhancement of the UV UC luminescence. PMID:20355618

Jiang, Tao; Qin, Weiping; Ding, Fuheng

2010-03-01

98

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

99

Synthesis and upconversion luminescence of uniform beta-NaYF4:Yb3+/Tm3+ hexagonal nanoplates.  

PubMed

Yb3+ and Tm3+-codoped hexagonal-phase NaYF4 powders were prepared by a facile hydrothermal method. The results of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) showed that the as-prepared powders were well crystallized nanoplates with high size-uniformity. Under the excitation from a 980 nm laser diode, upconversion (UC) emissions centered at approximately 291 nm (1I6 --> 3H6), approximately 346 nm (1I6 --> 3F4), approximately 361 nm (1D2 --> 3H6), approximately 451 nm (1D2 --> 3F4), approximately 474 nm (1G4 --> 3H6), approximately 644 nm (1G4 --> 3F4), and approximately 799 nm (3H4 --> 3H6) were observed in the sample. Furthermore, the intensity dependence of UC emissions on excitation power was measured. The results indicated that populating the 1I6, 1D2, 1G4, and 3H4 states were five-photon, four-photon, three-photon, and two-photon UC processes, respectively. PMID:22413250

Tian, Qijun; Liu, Ning; Qin, Guanshi; Zheng, Kezhi; Zhang, Daisheng; Qin, Weiping

2011-11-01

100

Synthesis and spectroscopic properties of GdAl3(BO3)4 poly-crystals codoped with Yb3+ and Eu3+.  

PubMed

GdAl3(BO3)4 polycrystals co-doped with Yb3+ and Eu3+ has been synthesised by combustion method with urea. Upon the excitation at 465 nm (Eu3+/7F6-->5D2 transition), emission bands centered at 590, 613, 697 and 702 nm in the wavelength region of 550-750 nm have clearly been observed, assigned to the electronic transitions of 5D0-->7FJ (J=1, 2, 4 and 5) of Eu3+ ions, respectively. Meanwhile, an intense emission centred at 980 nm along with a shoulder at 1,040 nm has also been observed by exploiting a cross-relaxation process between the transitions of Eu3+/5D0-->7F6 and Yb3+/2F7/2-->2F5/2. On the contrary, an intense red up-conversion emission centred at 613 nm originated from the 5D0-->7F2 transition of Eu3+ has been observed upon excitation with 980 nm laser diode. The quadratic dependence of the red up-conversion intensity on the pump-laser power reveals a cooperative energy transfer mechanism from a pair of Yb3+ ions to one Eu3+ ion. PMID:18594951

Yang, C H; Yang, G F; Pan, Y X; Zhang, Q Y

2008-07-02

101

Ultraviolet-driven white light generation from oxyfluoride glass co-doped with Tm3+-Tb3+-Eu3+  

NASA Astrophysics Data System (ADS)

Tm3+-Tb3+-Eu3+ co-doped oxyfluoride glasses, doped with about 3.0 mol. % TmF3, 0.25 mol. % TbF3, and 0.25 mol. % EuF3, have been prepared by melt quenching technique. Under excitation at commercial 365 nm, the rare-earth co-dopants are all directly excited and emit in the blue, green, and red, respectively, without appreciable energy transfer amongst the co-dopants. Tint of the white luminescence can be adjusted by changing the ratio of the co-dopants. Properties of the glass host promote excellent dissolution of the co-dopants and low non-radiative decay rate. The white emission at 365 nm excitation is suitable for light emitting diodes applications.

Kuznetsov, A. S.; Nikitin, A.; Tikhomirov, V. K.; Shestakov, M. V.; Moshchalkov, V. V.

2013-04-01

102

Organic salt assisted colloidal synthesis and X-ray luminescence of (Tm, Tb, Eu)-doped LaOBr nanocrystals  

NASA Astrophysics Data System (ADS)

The solution-phase synthesis of high quality LaOBr nanocrystals has been realized by single source precursors under the assistance of an organic salt (TBAB) and characterized by XRD and TEM. The unique crystallization process of LaOBr NCs is demonstrated and dictated by the amidation reaction. The X-ray luminescence of (Tm, Tb, Eu)-doped LaOBr NCs has also been characterized.The solution-phase synthesis of high quality LaOBr nanocrystals has been realized by single source precursors under the assistance of an organic salt (TBAB) and characterized by XRD and TEM. The unique crystallization process of LaOBr NCs is demonstrated and dictated by the amidation reaction. The X-ray luminescence of (Tm, Tb, Eu)-doped LaOBr NCs has also been characterized. Electronic supplementary information (ESI) available: Experimental, synthesis and characterisation details. See DOI: 10.1039/c2nr32780e

Zhang, Qiang; Yan, Bing; Lei, Fang; Chen, Hao-Hong

2012-11-01

103

Organic salt assisted colloidal synthesis and X-ray luminescence of (Tm, Tb, Eu)-doped LaOBr nanocrystals.  

PubMed

The solution-phase synthesis of high quality LaOBr nanocrystals has been realized by single source precursors under the assistance of an organic salt (TBAB) and characterized by XRD and TEM. The unique crystallization process of LaOBr NCs is demonstrated and dictated by the amidation reaction. The X-ray luminescence of (Tm, Tb, Eu)-doped LaOBr NCs has also been characterized. PMID:23128851

Zhang, Qiang; Yan, Bing; Lei, Fang; Chen, Hao-Hong

2012-11-06

104

Stem cell labeling using polyethylenimine conjugated (?-NaYbF4:Tm3+)/CaF2 upconversion nanoparticles.  

PubMed

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. PMID:23606911

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

2013-03-20

105

Crystal structures and stability of trigonal KLnF4 fluorides (Ln = Y, Ho, Er, Tm, Yb).  

PubMed

Crystal structures of pure and doped KLnF(4) (Ln = Y, Ho, Er, Tm, Yb) grown hydrothermally were studied with synchrotron single-crystal and powder diffraction as a function of temperature and pressure. At atmospheric conditions, KHoF(4) and KErF(4) crystallize in space group P3(1), while KTmF(4), Er:KYbF(4), and KYF(4) crystallize in space group P3(2). In both enantiomorphic structures, the K(+) and Ln(3+) cations are completely ordered. The pseudo-symmetry of the structures with respect to the two minimal supergroups k = 3 (P3(1) and P3(2)) and t = 2 (P3(1)12 and P3(2)12) increases with decreasing radius of the Ln(3+) cation, respectively. No phase transition is detected in KYF(4) at low temperatures down to 100 K at atmospheric pressure. Er:KYbF(4) and KYF(4) undergo irreversible pressure-induced phase transitions at about 4 GPa. In each case, the single crystals become fragmented into several crystallites as observed during single-crystal measurements in diamond anvil cells. Up to the phase transitions, both Er:KYbF(4) and KYF(4) are more compressible along the c axis and their bulk compressibility predominantly results from the contraction of the KF(8) polyhedra. The application of pressure does not affect the distribution of the cations in the crystal structures of Er:KYbF(4) and KYF(4) up to the phase transitions at about 4 GPa. PMID:23079894

Grzechnik, Andrzej; Khaidukov, Nicholas; Friese, Karen

2012-10-19

106

Structure and Properties of Single Crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2  

SciTech Connect

Single crystals of CaMg{sub 2}Bi{sub 2}, EuMg{sub 2}Bi{sub 2}, and YbMg{sub 2}Bi{sub 2} were obtained from a Mg-Bi flux cooled to 650 C. These materials crystallize in the CaAl{sub 2}Si{sub 2} structure-type (P3{bar m}1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg{sub 2}Bi{sub 2} displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg{sub 2}Bi{sub 2} reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) x 10{sup 19} cm{sup -3} for CaMg{sub 2}Bi{sub 2}, 1.7(1) x 10{sup 19} cm{sup -3} for EuMg{sub 2}Bi{sub 2}, and 4.6(7) x 10{sup 19} cm{sup -3} for YbMg{sub 2}Bi{sub 2}, which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios {rho}(300 K)/{rho}(10 K) {le} 1.6 in all cases, indicating significant defect scattering.

May, Andrew F [ORNL; McGuire, Michael A [ORNL; Singh, David J [ORNL; Custelcean, Radu [ORNL; Jellison Jr, Gerald Earle [ORNL

2011-01-01

107

Structure and properties of single crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2.  

PubMed

Single crystals of CaMg(2)Bi(2), EuMg(2)Bi(2), and YbMg(2)Bi(2) were obtained from a Mg-Bi flux cooled to 650 °C. These materials crystallize in the CaAl(2)Si(2) structure-type (P ?3m1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg(2)Bi(2) displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg(2)Bi(2) reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) × 10(19) cm(-3) for CaMg(2)Bi(2), 1.7(1) × 10(19) cm(-3) for EuMg(2)Bi(2), and 4.6(7) × 10(19) cm(-3) for YbMg(2)Bi(2), which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios ?(300 K)/?(10 K) ? 1.6 in all cases, indicating significant defect scattering. PMID:21999768

May, Andrew F; McGuire, Michael A; Singh, David J; Custelcean, Radu; Jellison, Gerald E

2011-10-14

108

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.

2013-03-01

109

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

NASA Astrophysics Data System (ADS)

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 (?), and their photoluminescence was studied by fluorescence spectrophotometry. The results indicate that the upconversion fluorescence of amine- and carboxyl-modified nanoparticles was enhanced after the surfaces of nanoparticles were modified. Compared to the upconversion fluorescence intensity of non-modified nanoparticles, the upconversion fluorescence intensities of amine- and carboxyl-modified nanoparticles were enhanced by 9.4 and 1.4 times, respectively. These results are attributed to the formation of the chemical bonds between Y2O3:Tm3+/Yb3+ core and non-crystalline SiO2 shell via Y-O-Si bridges, which activate the 'dormant' Tm3+/Yb3+ ions on the surfaces of nanoparticles. The results of the solubility investigations for amine- and carboxyl-modified nanoparticles indicate that severe aggregation can be weakened by adhering amino or carboxylic functional groups to the surfaces of nanoparticles. It is therefore concluded that the good hydrophilicity resulting from active functional groups in solutions and more intense upconversion fluorescence enable the doped core-shell nanoparticles to have great potential to be used as fluorescence biolabels in the future.

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

2008-04-01

110

Optical properties of trigonal single crystals (Yb,Tm)Al3(BO3)4 grown from fluxes based on the bismuth and lithium molybdates  

NASA Astrophysics Data System (ADS)

The conditions for synthesis of Yb x Tm1 - x Al3(BO3)4 ( x = 0, 0.1, 0.2, 1.0) single crystals from fluxes based on bismuth trimolybdate Bi2Mo3O12 and lithium molybdate Li2MoO4 are investigated. It is proposed to grow them by the group method on seeds. The polarized optical absorption spectra are measured for two mutually orthogonal linear polarizations at temperatures of 100 and 300 K.

Temerov, V. L.; Sokolov, A. É.; Sukhachev, A. L.; Bovina, A. F.; Édel'Man, I. S.; Malakhovski?, A. V.

2008-12-01

111

Upconversion Based Tunable White-Light Generation in Ln:Y 2 O 3 Nanocrystalline Phosphor (Ln = Tm\\/Er\\/Yb)  

Microsoft Academic Search

We report the generation of efficient white light based on upconversion (UC) in Tm3+\\/Er3+\\/Yb3+:Y2O3 nanocrystalline phosphor synthesized by simple and cost effective solution combustion technique on 976 nm laser excitation.\\u000a The calculated color coordinates (using 1931 CIE standard) for samples annealed at different temperatures vary from (0.16,\\u000a 0.30) to (0.32, 0.33) with dopant concentration, annealing temperature and the pump power; thus

Neeraj Kumar Giri; Kavita Mishra; S. B. Rai

112

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

113

Hydrothermal synthesis of NaLuF4:153Sm,Yb,Tm nanoparticles and their application in dual-modality upconversion luminescence and SPECT bioimaging.  

PubMed

Upconversion luminescence (UCL) properties and radioactivity have been integrated into NaLuF(4):(153)Sm,Yb,Tm nanoparticles by a facile one-step hydrothermal method, making these nanoparticles potential candidates for UCL and single-photon emission computed tomography (SPECT) dual-modal bioimaging in vivo. The introduction of small amount of radioactive (153)Sm(3+) can hardly vary the upconversion luminescence properties of the nanoparticles. The as-designed nanoparticles showed very low cytotoxicity, no obvious tissue damage in 7 days, and excellent in vitro and in vivo performances in dual-modal bioimaging. By means of a combination of UCL and SPECT imaging in vivo, the distribution of the nanoparticles in living animals has been studied, and the results indicated that these particles were mainly accumulated in the liver and spleen. Therefore, the concept of (153)Sm(3+)/Yb(3+)/Tm(3+) co-doped NaLuF(4) nanoparticles for UCL and SPECT dual-modality imaging in vivo of whole-body animals may serve as a platform for next-generation probes for ultra-sensitive molecular imaging from the cellular scale to whole-body evaluation. It also introduces an easy methodology to quantify in vivo biodistribution of nanomaterials which still needs further understanding as a community. PMID:23117216

Yang, Yang; Sun, Yun; Cao, Tianye; Peng, Juanjuan; Liu, Ying; Wu, Yongquan; Feng, Wei; Zhang, Yingjian; Li, Fuyou

2012-10-29

114

Honeycombs of triangles and magnetic frustration in SrL2O4 ( L=Gd , Dy, Ho, Er, Tm, and Yb)  

NASA Astrophysics Data System (ADS)

The crystal structures, magnetic order, and susceptibility have been investigated for magnetically frustrated SrDy2O4 , SrHo2O4 , SrEr2O4 , SrTm2O4 , and SrYb2O4 . Powder neutron-diffraction structural refinements reveal columns of LO6 octahedra that run along one crystallographic direction, with Sr-O polyhedra in the interstices. The lanthanide sublattice displays multiple triangular interconnections: one-dimensional strings form the backbones of four types of chains of lanthanide triangles sharing edges arranged in a honeycomb pattern. This crystal structure produces strong geometric frustration for the magnetic system that is evidenced in both magnetic susceptibility and neutron-scattering data at low temperatures. The susceptibility measurements for the series, including SrGd2O4 for which data are also reported, lack the sharp features characteristic of three-dimensional long-range magnetic ordering. Metamagnetic behavior is observed in the magnetization vs applied field data at 1.8 K for the cases of L=Dy , Er, and Ho. Magnetic neutron-scattering studies for the Dy and Er materials show only very broad magnetic scattering at low temperatures, while the Ho system exhibits long-range two-dimensional order. Any magnetic scattering in the Tm and Yb compounds, if present, was too weak to be detected in these measurements.

Karunadasa, H.; Huang, Q.; Ueland, B. G.; Lynn, J. W.; Schiffer, P.; Regan, K. A.; Cava, R. J.

2005-04-01

115

Upconversion emission enhancement of Gd3+ ions induced by surface plasmon field in Au@NaYF4 nanostructures codoped with Gd(3+)-Yb(3+)-Tm(3+) ions.  

PubMed

Au nanoparticles (NPs) attached ?-NaYF(4) nanocrystals codoped with Gd(3+)-Yb(3+)-Tm(3+) were synthesized by a facial solution method. The UV-vis-near-infrared absorption spectrum shows typical surface plasmon resonance band of Au NPs in addition to the characteristic absorption peaks of Yb(3+) ion. X-ray diffraction and selected area electron diffraction results indicate the existence of Au NPs. The transmission electron microscopic image reveals the formation of Au@NaYF(4) nanostructures. Enhanced ultraviolet (UV) upconversion luminescence (UCL) was observed in the nanostructures under the excitation of 980-nm infrared laser. The largest enhancement factor was obtained as 76 for the (6)I(J)?(8)S(7/2) emission of Gd(3+) ions, which was much larger than those emission enhancement factors of Tm(3+). It is for the first time to our knowledge that the emission enhancement of Gd(3+) ions was obtained. Local field enhancement induced by Au NPs was found to be responsible for the UCL enhancement, which is the further experimental evidence of local field enhancement theory. Magnetic measurements of the Au@NaYF(4) nanostructure indicated it would have potential application in magnetic resonance imaging. PMID:22515994

Jiang, Tao; Liu, Ye; Liu, Shusen; Liu, Ning; Qin, Weiping

2012-04-01

116

Photoluminescence and preparation of ZnNb 2O 6 doped with Eu 3+ and Tm 3+ nanocrystals for solar cell  

Microsoft Academic Search

Synthesis and luminescence properties of Eu3+ and Tm3+-doped ZnNb2O6 nanocrystals by the sol–gel process were investigated. The products were characterized by differential thermal analysis (DTA), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). ZnNb2O6:Eu3+ shows bright red luminescence with maximum peak at 613nm attributed to 5D0?7F2 transition. The major blue emission peak of ZnNb2O6:Tm3+ was at 483nm, corresponding to the

Yu-Jen Hsiao; Te-Hua Fang; Liang-Wen Ji

2011-01-01

117

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

118

Brilliant blue, green and orange-red emission band on Tm3+-, Tb3+- and Eu3+-doped ZrO2 nanocrystals  

Microsoft Academic Search

Tm3+-, Tb3+- and Eu3+-doped ZrO2 nanocrystals were prepared by a facile precipitation method with a hydrothermal process. Structural characterization showed a crystallite size ranging from 30 to 40 nm, and monoclinic and tetragonal zirconia phases were observed depending on the dopant concentration. The monoclinic phase was dominant for 0.5 mol% of Tb3+ and Eu3+, and the tetragonal phase was 100%

V. H. Romero; E. De la Rosa; T. López-Luke; P. Salas; C. Angeles-Chavez

2010-01-01

119

Controlled growth, intense upconversion emissions and concentration induced luminescence switching of bifunctional Tm3+ doped hexagonal NaYb0.55Gd0.45F4 nanorods  

NASA Astrophysics Data System (ADS)

Bifunctional hexagonal Tm3+ 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 980 nm 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 480 nm and 450 nm is observed by adjusting Tm3+ doping concentration. Based on power-dependent spectral analyses, it is found that with the increase of Tm3+ doping concentration, due to the suppressed saturation effect, the dominative UC process redistribute the populations at 1G4 and 1D2(Tm3+) states of Tm3+ 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.

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

2013-11-01

120

Charge disproportionation in RNiO3 (R= Tm, Yb) perovskites observed in situ by neutron diffraction and 57Fe probe Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

An in-situ investigation from high-resolution neutron powder diffraction data on the structural evolution of TmNiO3 and YbNiO3 perovskites across the metal-insulator transition, with TMI = 596 K and 598 K, respectively, allowed the charge disproportionation effect that these perovskites experience upon electronic localization below TMI to be followed. In the insulating (semiconducting) regime, the perovskites are monoclinic, space group P21/n, containing two inequivalent Ni1(3+?)+ and Ni2(3??)+ cations; above TMI, the samples become orthorhombic, space group Pbnm, with a single site for Ni3+. The 57Fe Mössbauer spectra of iron-doped (at 1.5%) RNiO3 (R = Tm, Yb) samples recorded below TMI exhibit for Fe1 and Fe2 (replacing Ni1 and Ni2 sites) hyperfine parameters corresponding to large (Ni1O6) and small (Ni2O6) octahedra. The remarkable difference between the quadrupole splittings (?1 ? 0.3 mm/s and ?2 ? 0.07 mm/s) of Fe1 and Fe2 sites in RNi0.985Fe0.015O3 is analyzed. We calculate the lattice contribution to the electric field gradient (EFG) at 57Fe ions, and estimate, by using the experimental ?1 and ?2 values, the contributions of the 3d, 3p, and 2p electrons (overlap distortion and covalence effects). Above TMI, a unique state for iron atoms is observed, upon metallization of the sample.

Alonso, J. A.; Martínez-Lope, M. J.; Presniakov, I. A.; Sobolev, A. V.; Rusakov, V. S.; Gapochka, A. M.; Demazeau, G.; Fernández-Díaz, M. T.

2013-05-01

121

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

122

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

123

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

124

Upconversion nanophosphors Naluf?:Yb,Tm for Lymphatic imaging in vivo by real-time upconversion luminescence imaging under ambient light and high-resolution X-ray CT.  

PubMed

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 NaLuF?-based UCNP (NaLuF?: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 NaLuF?:Yb,Tm nanoparticles can also be used as an X-ray CT imaging agent to enhance the imaging depth and in vivo imaging resolution. PMID:23650481

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

2013-04-23

125

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

126

Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance.  

SciTech Connect

Monoclinic potassium rare-earth double tungstates [KRE(WO{sub 4}){sub 2}, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln{sup 3+}) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb{sup 3+}- and Tm{sup 3+}-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

Raghothamachar, B.; Carvajal, J; Pujol, M; Mateos, X; Sole, R; Aguilo, M; Diaz, F; Dudley, M

2010-01-01

127

Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance  

NASA Astrophysics Data System (ADS)

Monoclinic potassium rare-earth double tungstates [KRE(WO4)2, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln3+) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb3+- and Tm3+-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

Raghothamachar, B.; Carvajal, J. J.; Pujol, M. C.; Mateos, X.; Solé, R.; Aguiló, M.; Díaz, F.; Dudley, M.

2010-06-01

128

Thermal conductivity of La/sub 3-x/R/sub x/S/sub 4/ R = Sm, Yb, and Eu  

SciTech Connect

The thermal diffusivity values of La/sub 2.7/Eu/sub 0.3/S/sub 4/, La/sub 2.2/Eu/sub 0.8/S/sub 4/, La/sub 2.7/Sm/sub 0.3/S/sub 4/, La/sub 2.3/Sm/sub 0.7/S/sub 4/, La/sub 2.7/Yb/sub 0.2/S/sub 4/, and La/sub 2.2/Yb/sub 0.7/S/sub 4/ were measured by the flash diffusivity method from 400/degree/C to 1000/degree/C. These values ranged from .007 cm/sup 2//s to .018 cm/sup 2//s. The thermal conductivities of the ternary rare earth sulfides were calculated from the thermal diffusivity data and ranged from 10.7 mW/cm/degree/C to 31.6 mW/cm/degree/C. The thermal diffusivity values of three thermal conductivity standards (armco iron, NBS graphite, and NBS austenitic stainless steel) obtained using the flash diffusivity apparatus agreed with the accepted values within a deviation of +-10%. Of the ternary rare earth sulfides measured, La/sub 2.2/Eu/sub 0.8/S/sub 4/ had the highest figure of merit at 1000/degree/C of .525. All these samples had an oxysulfide present at the grain boundaries which degraded their high temperature thermoelectric performance. 56 refs., 12 figs., 7 tabs.

Kokos, G.B.

1989-02-01

129

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

130

Core-shell Fe3O4@NaLuF4:Yb,Er/Tm nanostructure for MRI, CT and upconversion luminescence tri-modality imaging.  

PubMed

Core-shell Fe(3)O(4)@NaLuF(4):Yb,Er/Tm nanostructure (MUCNP) with multifunctional properties has been developed using a step-wise synthetic method. The successful fabrication of MUCNP has been confirmed by transmission electron microscopy, powder X-ray diffraction, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. The MUCNP exhibits superparamagnetic property with saturation magnetization of 15 emu g(-1), and T(2)-enhanced magnetic resonance (MR) effect with an r(2) value of 21.63 s(-1) mM(-1) at 0.5 T, resulting from the Fe(3)O(4) cores. Moreover, the NaLuF(4)-based MUCNP provides excellent X-ray attenuation and upconversion luminescence (UCL) emission under excitation at 980 nm. In vivo MR, computed tomography (CT) and UCL images of tumor-bearing mice show that the MUCNP can be successfully used in multimodal imaging. In vitro tests reveal that the MUCNP is non-cytotoxic. These results suggest that the developed MUCNP could be served as an MR, CT and UCL probe for tri-modality imaging. PMID:22444645

Zhu, Xingjun; Zhou, Jing; Chen, Min; Shi, Mei; Feng, Wei; Li, Fuyou

2012-03-22

131

Structural and thermoelectric properties of BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu)  

SciTech Connect

The structure and thermoelectric properties of a series of barium lanthanide cobaltites, BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu), which were prepared using the spark plasma synthesis technique, have been investigated. The space group of these compounds was re-determined and confirmed to be P31c instead of the reported P6{sub 3}mc. The lattice parameters a and c range from 6.26279(2) Angst to 6.31181(6) Angst , and from 10.22468(6) Angst to 10.24446(15) Angst for R = Lu to Dy, respectively. The crystal structure of BaRCo{sub 4}O{sub 7} is built up from Kagome sheets of CoO{sub 4} tetrahedra, linked by triangular layers of CoO{sub 4} tetrahedra. The values of figure of merit (ZT) of the BaRCo{sub 4}O{sub 7} samples were determined to be around 0.02 at 800 K. X-ray diffraction patterns of these samples have been determined and submitted to the Powder Diffraction File.

Wong-Ng, W.; Yan, Y.; Liu, G. [Ceramics Division, NIST, Gaithersburg, Maryland 20899 (United States); Xie, W.; Tritt, T. [Department of Physics, Clemson University, Greensville, South Carolina 29634 (United States); Kaduk, J. [Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Thomas, E. [Air Force Research Laboratory, Wright Pattersen, Ohio 45433 (United States)

2011-12-01

132

Syntheses, and crystal and electronic structures of the new Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb): Structural relationship with Yb{sub 2}CdSb{sub 2} and the solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2}  

SciTech Connect

Presented are the details of the syntheses, crystal and electronic structures of a new family of Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb), as well as the solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2}. The structures of Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb) were determined to be of a new type with the non-centrosymmetric space group Pmc2{sub 1} (no. 26), Pearson symbol oP12, with lattice parameters a=4.684(1)-4.788(1) A; b=9.099(3)-9.117(2) A; c=7.837(1)-8.057(2) A for the Na{sub 2}ACdSb{sub 2} series, and a=4.6637(9)-5.0368(8) A; b=9.100(2)-9.8183(15) A; and c=7.7954(15)-8.4924(13) A for K{sub 2}ACdSb{sub 2}, respectively. The solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (x{approx}1) are isostructural and isoelectronic to the recently reported Yb{sub 2}CdSb{sub 2} (space group Cmc2{sub 1} (no. 36), Pearson symbol cP20). All discussed structures are based upon CdSb{sub 2}{sup 4-} polyanionic layers, similar to the ones observed in Yb{sub 2}CdSb{sub 2}, with various alkali- and/or alkaline-earth cations coordinated to them. Magnetic susceptibility and Seebeck coefficient measurements on selected Eu{sub 2-x}Yb{sub x}CdSb{sub 2} samples, taken at low temperatures up to 300 K, are also reported. -- Graphical abstract: The quaternary Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb) with novel layered structures have been synthesized for the first time and structurally characterized by single-crystal X-ray diffraction. Reported as well are the results from crystallographic and property studies of the closely related solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} (x{approx}1), and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1Eu, Yb) are new quaternary Zintl phases. {yields} Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} (x{approx}1), and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1

Saparov, Bayrammurad; Saito, Maia [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen, E-mail: bobev@udel.ed [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)

2011-02-15

133

Rare-Earths Centers (Sm3+, Eu3+, Yb3+) in MeF2 (Me = Ca, Sr, Ba, Cd) Crystals  

NASA Astrophysics Data System (ADS)

Rare-earth elements RE3+ (RE = Sm, Eu, Yb) form impurity centers in fluorite-like crystals MeF2 (Me = Ca, Sr, Ba, Cd). The crystal structure of cubic, trigonal and tetragonal centers in MeF2 has been investigated in the framework of shell model and pair potential approximation. The crystal field parameters were calculated with the exchange charges model, using the optimized geometry of the doped host matrix. With these parameters we have been calculated the optical spectra and spin-Hamiltonian (g-factors) of RE3+ in MeF2, for some combination of R3+ and MeF2. The obtained results were discussed and comparison with experimental data was made. A good agreement confirms the method and model of calculations.

Nikiforov, A. E.; Avram, N. M.; Chernyshev, V. A.; Volodin, V. P.; Avram, C. N.; Vaida, M.

2010-08-01

134

Optical temperature sensing of NaYbF4: Tm3+ @ SiO2 core-shell micro-particles induced by infrared excitation.  

PubMed

NaYbF4:Tm3+@SiO2 core-shell micro-particles were synthesized by a hydrothermal method and subsequent ultrasonic coating process. Optical temperature sensing has been observed in NaYbF4: Tm3+@SiO2 core-shell micro-particles with a 980 nm infrared laser as excitation source. The fluorescence intensity ratios, optical temperature sensitivity, and temperature dependent population re-distribution ability from the thermally coupled 1D2 /1G4 and 3F2 /3H4 levels of the Tm3+ ion have been analyzed as a function of temperature in the range of 100~700 K in order to check its availability as a optical temperature sensor. A better behavior as a low-temperature sensor has been obtained with a minimum sensitivity of 5.4 × 10-4 K-1 at 430 K. It exhibits temperature induced population re-distribution from 1D2 /1G4 thermally coupled levels at higher temperature range. PMID:24104034

Wang, Xiangfu; Zheng, Jin; Xuan, Yan; Yan, Xiaohong

2013-09-01

135

Hydrogen impurity effects. A(5)Tt(3)Z intermetallic compounds between A = Ca, Sr, Ba, Eu, Yb and Tt = Sn, Pb with Cr(5)B(3)-like structures that are stabilized by hydride or fluoride (Z).  

PubMed

The binary systems Ca-Sn, Ba-Sn, Eu-Sn, Yb-Sn, Sr-Pb, Ba-Pb, and Eu-Pb do not contain Cr(5)B(3)-like A(5)Tt(3) phases when care is taken to exclude hydrogen from the reactions (Tt = tetrel, Si-Pb). All form ternary A(5)Tt(3)H(x)() phases (x < or = 1) with "stuffed" Cr(5)B(3)-like structures instead, and all of those tested, Ca-Sn, Ba-Sn, Sr-Pb, and Ba-Pb, also yield the isostructural A(5)Tt(3)F. The structures and compositions of Ca(5)Sn(3)H(x), Ca(5)Sn(3)F(0.89), Eu(5)Sn(3)H(x), and Sr(5)Pb(3)F have been refined from single-crystal X-ray diffraction data and of Ca(5)Sn(3)D from powder neutron data. The interstitial H, F atoms are bound in a tetrahedral (A(2+))(4) cavity in a Cr(5)B(3)-type metal atom structure. Nine previous reports of binary "Ba(5)Sn(3)", "Yb(5)Sn(3)", "Sr(5)Pb(3)", and "Ba(5)Pb(3)" compounds were wrong and presumably concerned the hydrides. The new ternary phases are generally Pauli-paramagnetic, evidently with pi electrons from the characteristic tetrelide dimers in this structure type at least partially delocalized into the conduction band. The Sn-Sn bonds appear correspondingly shortened on oxidation. Other new phases reported are CaSn (CrB type), Yb(5)Sn(4)H(x) (Sm(5)Ge(4)), YbSn ( approximately TlTe), Ba(5)Pb(3) ( approximately W(5)Si(3)), and Yb(31)Pb(20) (Ca(31)Sn(20)). PMID:11300823

Leon-Escamilla, E A; Corbett, J D

2001-03-12

136

Synthesis, characterization, and magnetic properties of new Rh(III) compounds with the KâCdClâ structure-type: SrâMRhOâ (M = Sm, Eu, Tb, Dy, Ho, Er, and Yb)  

Microsoft Academic Search

The compounds SrâMRhOâ (M = Sm, Eu, Tb, Dy, Ho, Er, and Yb) have been synthesized and structurally characterized by Rietveld refinement of powder X-ray diffraction data in the space group R{bar 3}c; Z = 6. The lattice parameters for the series were found to be a = 9.78570(7) and c = 11.4811(1) â«, a = 9.7837(1) and c =

R. C. Layland; S. L. Kirkland; H. C. zur Loye

1998-01-01

137

Highly uniform and monodisperse GdOF:Ln(3+) (Ln = Eu, Tb, Tm, Dy, Ho, Sm) microspheres: hydrothermal synthesis and tunable-luminescence properties.  

PubMed

GdOF:Ln(3+) (Ln = Eu, Tb, Tm, Dy, Ho and Sm) microspheres (1.5 ?m) with high uniformity and monodispersity have been synthesized via a facile hydrothermal method followed by heat treatment (600 °C). X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the resulting samples. A series of controlled experiments indicate that sodium citrate (Cit(3-)) as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the dosage of Cit(3-) and pH values in the initial solution. The possible formation mechanism for these microspheres has been presented. Under UV light and low-voltage electron beam excitation, GdOF:Ln(3+) microspheres show the characteristic f-f transitions of Ln(3+) (Eu, Tb/Ho, Tm, Dy and Sm) ions and give bright red, green, blue, yellow and yellowish-orange emission, respectively. In addition, multicolored luminescence containing white emission have been successfully confected for co-doped GdOF:Ln(3+) phosphors by changing the doped Ln(3+) ions and adjusting their doping concentrations due to the simultaneous luminescence of Ln(3+) in the GdOF host, making these materials have potential applications in field-emission display devices. PMID:23942823

Zhang, Yang; Kang, Xiaojiao; Geng, Dongling; Shang, Mengmeng; Wu, Yuan; Li, Xuejiao; Lian, Hongzhou; Cheng, Ziyong; Lin, Jun

2013-09-18

138

Two new ternary lanthanide antimony chalcogenides: Yb4Sb2S11.25 and Tm4Sb2Se11.68 containing chalcogenide Q2- and dichalcogenide (Q2)2- anions  

NASA Astrophysics Data System (ADS)

Dark red and dark brown crystals of Yb4Sb2S11.25 and Tm8Sb4Se11.68, respectively, were obtained from the reaction of the elements in Sb2Q3 (Q=S, Se) fluxes. Both non-stoichiometric compounds are orthorhombic and crystallize in the same space group Pnnm, with two formula units per unit cell (a=12.446(2), b=5.341(1), c=12.058(2) for sulfide and a=13.126(2), b=5.623(1), c=12.499(2) for the selenide). Their crystal structures are dominated by lanthanide-chalcogenide polyhedra (CN=7 and 8), which share corners, edges, triangular- and square-faces to form a three-dimensional framework embedding antinomy cations. The latter are coordinated by three sulfide anions with 5(1+2+2) secondary contacts forming basically infinite chains running along [0 1 0]. The chalcogens in both compounds form chalcogenide Q2- and dichalcogenide (Q2)2- anionic units. The optical analysis made on those compounds shows that both are semiconductors with band gap of 1.71 and 1.22 eV for Yb4Sb2S11.25 and Tm4Sb2Se11.75, respectively.

Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

2012-03-01

139

Critical behavior of the paramagnetic to antiferromagnetic transition in orthorhombic and hexagonal phases of RMnO3 (R=Sm, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y)  

NASA Astrophysics Data System (ADS)

The critical behavior of the paramagnetic to antiferromagnetic transition in RMnO3 (R = Sm, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) has been studied with an ac photopyroelectric calorimeter, which gives simultaneously the thermal diffusivity and specific heat as a function of temperature with high resolution around the Néel temperature. RMnO3 (R = Sm, Tb, Dy) has an orthorhombic perovskite structure, whereas the other manganites are hexagonal, thus revealing a strong thermal anisotropy. SmMnO3 with type-A antiferromagnetic ordering exhibits a 3D-XY critical behavior, which could be attributed to the peculiar site anisotropy of Sm3+ and the exchange interaction between Mn3+ and Sm3+ ions. The sinusoidal spin ordering in TbMnO3 and DyMnO3 can be phenomenologically described by the 3D-Heisenberg model. Finally, the hexagonal manganites RMnO3 (R = Ho, Er, Tm, Yb, Lu, Y) are close to the 3D-Heisenberg universality class, ruling out the chiral models predicted by the renormalization group theory.

Oleaga, A.; Salazar, A.; Prabhakaran, D.; Cheng, J.-G.; Zhou, J.-S.

2012-05-01

140

Spectroscopic properties of Y3TaO7 powders activated with Eu, Er and co-activated with Yb  

Microsoft Academic Search

A new synthesis method of Y3TaO7 is reported. Pure phase powders were prepared by modified Pechini technique. Precursors obtained through that route were heated at the temperature about 1000°C with or without use of Li2SO4 flux. That implicates in different morphology of specimens and also their spectroscopic properties. Eu ions were used as a spectroscopic probe to prove inhomogeneous broadening

Adam Walasek; Eugeniusz Zych; An Liqiong; Jian Zhang; Shiwei Wang

2007-01-01

141

Electronic structure and electron-phonon coupling in stoichiometric and defective hydrides MPdH3 (M=Ca, Sr, Eu, Yb)  

NASA Astrophysics Data System (ADS)

On the basis of electron transfer from the divalent element to the PdH3 entities, the perovskite structure MPdH3 (M=Sr, Eu, Yb) are expected to have similar electronic states at the Fermi energy as superconducting Pd-Hx and Pd-noble-metal-Hx and thus could be potential candidates for superconductivity. With this motivation, we have investigated the electronic structure and some aspects of the electron-phonon coupling in these hydrides using the ab initio augmented plane-wave method, and the results of the energy bands, the total and partial wave analysis of the density of states, and the electronic contribution, ?H to the electron-phonon coupling are presented. Similar studies for the hydrogen defective material CaPdH2 are also included. We have found that all these compounds are metallic with essentially filled Pd-d bands and a small density of states at Fermi level as in PdH. Nevertheless, the calculated values of ?H, which govern the contribution of the hydrogen atoms to the electron-optical phonon coupling parameter ?, although sizeable, are lower than in PdH. This would indicate that these compounds, if superconducting, would have lower values of the superconducting transition temperatures Tc than in PdH.

Orgaz, Emilio; Mazel, Vincent; Gupta, Michèle

1996-12-01

142

Observation of superconductivity at 30~46K in AxFe2Se2 (A = Li, Na, Ba, Sr, Ca, Yb, and Eu)  

PubMed Central

New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30?K in KFe2Se2, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced Tc = 30?46?K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a?3.755–3.831 Å while c?15.99–20.54 Å. Resistivities show the corresponding sharp transitions at 45?K and 39?K for NaFe2Se2 and Ba0.8Fe2Se2, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well.

Ying, T. P.; Chen, X. L.; Wang, G.; Jin, S. F.; Zhou, T. T.; Lai, X. F.; Zhang, H.; Wang, W. Y.

2012-01-01

143

Spectroscopic investigations of Nd3+-, Er3+-, Er3+/Yb3+-, and Tm3+-ions doped SiO2-Al2O3-CaF2-GdF3 glasses  

NASA Astrophysics Data System (ADS)

This paper reports on the absorption, visible and near-infrared luminescence properties of Nd3+, Er3+, Er3+/2Yb3+, and Tm3+ doped oxyfluoride aluminosilicate glasses. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters (?2, ?4 and ?6) have been calculated for all the studied ions. Decay lifetime curves were measured for the visible emissions of Er3+ (558 nm, green), and Tm3+ (650 and 795 nm), respectively. The near infrared emission spectrum of Nd3+ doped glass has shown full width at half maximum (FWHM) around 45 nm (for the 4F3/2?4I9/2 transition), 45 nm (for the 4F3/2?4I11/2 transition), and 60 nm (for the 4F3/2?4I13/2 transition), respectively, with 800 nm laser diode (LD) excitation. For Er3+, and Er3+/2Yb3+ co-doped glasses, the characteristic near infrared emission bands were spectrally centered at 1532 and 1544 nm, respectively, with 980 nm laser diode excitation, exhibiting full width at half maximum around 50 and 90 nm for the erbium 4I13/2?4I15/2 transition. The measured maximum decay times of 4I13/2?4I15/2 transition (at wavelength 1532 and 1544 nm) are about 5.280 and 5.719 ms for 1Er3+ and 1Er3+/2Yb3+ (mol%) co-doped glasses, respectively. The maximum stimulated emission cross sections for 4I13/2?4I15/2 transition of Er3+ and Er3+/Yb3+ are 10.81×10-21 and 5.723×10-21 cm2. These glasses with better thermal stability, bright visible emissions and broad near-infrared emissions should have potential applications in broadly tunable laser sources, interesting optical luminescent materials and broadband optical amplification at low-loss telecommunication windows.

Lakshminarayana, G.; Mao, Mengfei; Yang, Rong; Qiu, J. R.; Brik, M. G.

2009-11-01

144

Crystal structures of RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) studied by single crystal X-ray diffraction  

SciTech Connect

The crystal structures of ternary compounds RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) have been elucidated from X-ray single crystal CCD data. All compounds are isotypic and crystallize in the tetragonal space group P4/mbm. The general formula RPt{sub 3-x}Si{sub 1-y} arises from defects: x{approx}0.20, y{approx}0.14. The crystal structure of RPt{sub 3-x}Si{sub 1-y} can be considered as a packing of four types of building blocks which derive from the CePt{sub 3}B-type unit cell by various degrees of distortion and Pt, Si-defects. - Graphical Abstract: Electron density in RPt{sub 3-x}Si{sub 1-y} at 0, 1/2 , 0.

Gribanov, Alexander [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Chemistry Department of the Moscow State University, Leninskie Gory, GSP-1, 119991 Moscow (Russian Federation); Grytsiv, Andriy [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Rogl, Peter, E-mail: peter.franz.rogl@univie.ac.a [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Seropegin, Yurii [Chemistry Department of the Moscow State University, Leninskie Gory, GSP-1, 119991 Moscow (Russian Federation); Giester, Gerald [Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse 14, A-1090 Wien (Austria)

2009-07-15

145

Effect of Eu 2CuO 4\\/Yttrium-stabilized Z rO 2 buffer layers on YB 2Cu 3O 7? x thin films grown on Si substrates  

Microsoft Academic Search

The microstructure and crystallinity of epitaxial YB2Cu3O7?x (YBCO) thin films grown on a silicon using a buffer of Eu2CuO4 (ECO)\\/Yttrium-stabilized ZrO2 (YSZ) were investigated by X-ray high-resolution diffraction, small angle reflection, and reciprocal space map, as well as atomic force microscopy. The results showed that YBCO films with a buffer of ECO\\/YSZ were well oriented in the [00L] direction perpendicular

X. L. Li; J. Gao; H. Y. Wong; Z. H. Mai

2005-01-01

146

Magnetism of cyano-bridged Ln3+-M3+ complexes. Part II: one-dimensional complexes (Ln3+ = Eu, Tb, Dy, Ho, Er, Tm; M3+ = Fe or Co) with bpy as blocking ligand.  

PubMed

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2'-bipyridine in water/ethanol led to 13 one-dimensional complexes: trans-[M(CN)4(mu-CN)2Ln(H2O)4(bpy)]n.4nH2O.1.5nbpy (Ln = Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Lu3+; M = Fe3+, Co3+). The structures for [EuFe]n (1), [TbFe]n (2), [DyFe]n (3), [HoFe]n (4), [ErFe]n (5), [TmFe]n (6), [LuFe]n (7), [EuCo]n (8), [TbCo]n (9), [DyCo]n (10), [HoCo]n (11), [ErCo]n (12), and [TmCo]n (13) have been solved: they crystallize in the triclinic space group P and are isomorphous. They exhibit a supramolecular architecture created by the interplay of coordinative, hydrogen bonding, and pi-pi interactions. A stereochemical study of the eight-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. The Ln3+-Fe3+ interaction is antiferromagnetic in [DyFe]n and [TbFe]n. For [EuFe]n, [HoFe]n, [ErFe]n, and [TmFe]n, there is no sign of any significant interaction. The magnetic behavior of [DyFe]n suggests the onset of weak long-range ferromagnetic ordering at 2.5 K. PMID:16180856

Figuerola, Albert; Ribas, Joan; Casanova, David; Maestro, Miguel; Alvarez, Santiago; Diaz, Carmen

2005-10-01

147

Synthesis and structural comparison of a series of divalent Ln(Tp(R,R)')2 (Ln = Sm, Eu, Yb) and trivalent Sm(Tp(Me2))2X (X = F, Cl, I, BPh4) complexes.  

PubMed

Reaction of LnI2 (Ln = Sm, Yb) with two equivalents of NaTp(Me2) or reduction of Eu(Tp(Me2))2OTf gives good yields of the highly insoluble homoleptic Ln(II) complexes, Ln(Tp(Me2))2 (Ln = Sm (1a), Yb (2a), Eu (3a)). Use of the additionally 4-ethyl substituted Tp(Me2,4Et) ligand produces the analogous, but soluble Ln(Tp(Me2,4Et))2 (1-3b) complexes. Soluble compounds are also obtained with the Tp(Ph) and Tp(Tn) ligands (Tn = thienyl), Ln(Tp(Ph))2 (Ln = Sm, 1c; Yb, 2c) and Ln(Tp(Tn))2 (Ln = Sm, 1d; Yb, 2d). To provide benchmark parameters for structural comparison the series of Sm(Tp(Me2))2X complexes (X = F, 1e; Cl, 1f; Br, 1g; I, 1h; BPh4, 1j) were prepared either via oxidation of the Sm(Tp(Me2))2 or salt metathesis from SmX3 (X = Cl, Br, I). The solid-state structures of 1-3a, 1b, 1-2c and 1e, 1f, 1h, and 1j were determined by single-crystal X-ray diffraction. The homoleptic bis-Tp complexes are all six-coordinate with trigonal antiprismatic geometries, planes of the kappa(3)-Tp ligands are parallel to one another. In the series of Sm(Tp(Me2))2X complexes the structure changes from seven-coordinate molecular compounds, with intact Sm-X bonds, for X = F, Cl, to six-coordinate ionic structures [Sm(Tp(Me2))2]X (X = I, BPh4), suitable crystals of the bromide compound could not be obtained. The dependence of the structures on the size of X is understandable in terms of the interplay between the size of the cleft that the [Sm(Tp(Me2))2](+) fragment can make available and the donor ability of the anionic group toward the hard Sm(III) center. PMID:11559067

Hillier, A C; Zhang, X; Maunder, G H; Liu, S Y; Eberspacher, T A; Metz, M V; McDonald, R; Domingos, A; Marques, N; Day, V W; Sella, A; Takats, J

2001-09-24

148

Low-temperature superstructures of a series of Cd6M (M = Ca, Y, Sr, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) crystalline approximants  

NASA Astrophysics Data System (ADS)

The low-temperature (LT) superstructure and the phase transition temperature have been investigated for a series of Cd6M crystalline approximants by transmission electron microscopy as well as electrical resistivity measurements. Except for M = Lu, Cd6M is found to undergo a phase transition to a monoclinic phase at a low temperature and the transition temperature (Tc) scales well with the size of the M atom. For M = Ca, Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm the LT superstructure is explained by a \\sqrt{2}a\\times a\\times \\sqrt{2}a lattice with the space group C2/c, and for M = Sr and Yb a \\sqrt{2}a\\times 2 a\\times \\sqrt{2}a monoclinic lattice with P2/m. On the other hand, no phase transition is observed for M = Lu, indicating that a Cd4 tetrahedron at the cluster center remains disordered down to the lowest temperature, i.e. 16 K. It is shown that the volume inside the Cd20 dodecahedron plays a crucial role in the occurrence of the phase transition, and long-term aging in particular promotes the phase transition for late rare-earth elements such as Ho, Er and Tm, suggesting that the transition is sensitive to and is even hindered by disorder such as atomic vacancies. The absence of the transition for M = Lu is attributed to the highest activation energy for the transition due to the smallest volume inside the Cd20 dodecahedron.

Nishimoto, Kazue; Sato, Takeru; Tamura, Ryuji

2013-06-01

149

(?-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

150

(?-NaYbF4:Tm(3+))/CaF2 core/shell nanoparticles with efficient near-infrared to near-infrared upconversion for high-contrast deep tissue bioimaging.  

PubMed

We describe the development of novel and biocompatible core/shell (?-NaYbF(4):Tm(3+))/CaF(2) nanoparticles that exhibit highly efficient NIR(in)-NIR(out) 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/cm(2)) is 0.6 ± 0.1%. This high UC PL efficiency is realized by suppressing surface quenching effects via heteroepitaxial growth of a biocompatible CaF(2) 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). PMID:22928629

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

2012-09-04

151

Enhanced ultraviolet upconversion luminescence of Tm and Yb codoped ZrF4-BaF2-LaF3-AlF3-NaF glass.  

PubMed

Ultraviolet (UV) upconversion (UC) luminescence properties of Tm3+ ions sensitized by Yb3+ ions in ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glass were studied in detail. Under the excitation from a 980 nm continuous wave (CW) diode laser, red, blue, and even UV emissions were observed in the fluorozirconate glass. Several fluorescence bands appeared in the UC emission spectrum from 292.8 nm to 805.8 nm. The UC emission peaks at 291 nm, 347 nm, 363 nm, 454 nm, 475 nm, 647 nm, 687 nm, and 804 nm correspond to the transitions of 1I6 --> 3H6, 1I6 --> 3F4, 1D2 --> 3H6, 1D2 --> 3F4, 1G4 --> 3H6, 1G4 --> 3F4, 3F3 --> 3H6, and 3H4 --> 3H6, respectively. Experimental results of intensity dependence of the up-converted fluorescence on the pump power indicate a five-photon excitation scheme of 1I6 energy level. PMID:22413235

He, Chunfeng; Zhao, Dan; Qin, Guanshi; Zheng, Kezhi; Qin, Weiping

2011-11-01

152

Room-temperature monoclinic distortion due to charge disproportionation in RNiO3 perovskites with small rare-earth cations (R=Ho, Y, Er, Tm, Yb, and Lu): A neutron diffraction study  

NASA Astrophysics Data System (ADS)

Polycrystalline samples of the strongly distorted RNiO3 (R=Ho, Y, Er, Tm, Yb, Lu) perovskites have been prepared under high hydrostatic pressure, at 20 kbar. The crystal structure in the insulating phase of these nickelates has been investigated by high-resolution neutron powder diffraction, below the metal-insulator (MI) transition that all of these compounds experience between 573 K (R=Ho) and 599 K (R=Lu). They present a subtle monoclinic distortion (s.g. P21/n) which implies the splitting of the Ni positions in the crystal. Ni1O6 and Ni2O6 octahedra exhibit very distinct mean Ni-O bond distances, interpreted as a charge disproportionation effect (2Ni3+-->Ni3+?+Ni3-?) which develops at the opening of the gap. In spite of the regular evolution of the ? angle, characterizing the monoclinic distortion, the average and distances do not significantly change along the series; i.e., the disproportionation parameter ? is about 0.3 electrons in the last six members of the RNiO3 series. The observed regular increase of the Ni1-O-Ni2 angles, governing the superexchange and the electronic transfer between Ni cations, accounts for the evolution of Néel and MI transition temperatures in these perovskites.

Alonso, J. A.; Martínez-Lope, M. J.; Casais, M. T.; García-Muñoz, J. L.; Fernández-Díaz, M. T.

2000-01-01

153

Large electric polarization in high pressure synthesized orthorhombic manganites RMnO3 (R=Ho,Tm,Yb and Lu) by using the double-wave PE loop measurements  

NASA Astrophysics Data System (ADS)

The magnitude of electric polarization via the conventional pyroelectric current and/or PE loop measurements often is ambiguous due to resistive components of the sample. To avoid this, a new technique called the double-wave method has been recently developed [1], in which only hysteretic PE components can be measured. Using this technique, we have measured the ferroelectric polarization of the orthorhombic RMnO3 (R=Ho, Tm, Yb, and Lu) synthesized under high pressure. Large remnant polarization Pr up to 920 ?C/m^2 is observed at 10 K for LuMnO3. Furthermore, the Pr vs. temperature data from the PE loop has shown consistency with that measured through the pyroelectric current measurements, supporting a theoretical prediction of large polarization in the E-type spin structure in this system [2]. We also discuss the influence of thermal histories on the ferroelectric domain dynamics and possible internal bias field effects originating from oxygen vacancies in RMnO3. [1] M. Fukunaga, et al. J. Phys. Soc. Jpn. 77, 064706 (2008). [2] I. A. Sergienko, et al. Phys. Rev. Lett., 97, 227204 (2006)

Chai, Y. S.; Oh, Y. S.; Manivannan, N.; Yang, Y. S.; Kim, Kee Hoon; Feng, S. M.; Wang, L. J.; Jin, C. Q.

2009-03-01

154

The high-pressure synthesis and characterization of some praseodymium-substituted rare-earth-based R{sub 2}Ba{sub 4}Cu{sub 7}O{sub 14-{delta}} (R = Nd, Eu, Tm)  

SciTech Connect

The formation of phases in the (R{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} (Pr-doped R247; R = Nd, Eu, Tm) system with x = 0-1.0 was investigated. Samples of the title series were synthesized at 980-990{degree}C at 25 bar O{sub 2}, followed by annealing at 300{degree}C under 130 bar O{sub 2} for 30 hr. Oxygen content of the samples has been determined by iodometric titration. Single-phased samples has been determined by iodometric titration. Single-phased samples were obtained with x smaller than or equal to 0.3, 0.4, and 0.4 for R = Nd, Eu, and Tm, respectively, as indicated by X-ray diffraction measurements. With increasing amount of Pr substituting for R, the cell dimensions of the Pr-doped R247 phases were found to expand steadily, whereas the corresponding structural orthorhombicity was observed to decrease systematically. Superconducting transition temperatures (T{sub c}`s) of the title phases were found to be significantly suppressed upon Pr doping, as indicated by field-cooled temperature-dependent magnetization studies. The effect of Pr substitution on T{sub c}`s of R247 (R = Y, Eu, Er, Tm, Nd, Dy) phases was investigated and compared as a function of R{sup 3+} radii, but no size dependence effect was observed. In addition, field-dependent magnetization studies for a series of (Eu{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} samples with x = 0, 0.2, and 0.4, respectively, are also reported.

Teng-Ming Chen; Kao, F.S. [National Chiao-Tung Univ., Taiwan (China)

1997-08-01

155

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

156

Enhancement of red emission by co-dopant Ln3+ ions in Eu3+:LaOF nanoparticles  

NASA Astrophysics Data System (ADS)

Fluoride nanoparticles of Ln3+ (Ln3+=Pr3+, Nd3+, Sm3+, Gd3+,Tb3+ Dy3+, Ho3+, Er3+, Tm3+, Yb3+)/Eu3+:LaOF and Eu3+:LaOF with rhombohedral crystal structure were prepared by a hydrothermal-sintering method. The red fluorescence emission of Eu3+ ions was found to be enhanced with most of the co-dopant Ln3+ ions. Compared with strong fluorescence emission at 610 nm of Eu3+:LaOF nanoparticles, the enhancement factors was up to ten times in Ln3+ (Ln3+=Gd3+, Dy3+, Tm3+)/Eu3+:LaOF co-doped nanoparticles. The results show that the asymmetry of the local environment of Eu3+ ion was reduced by co-doping Ln3+ ion into the nanoparticles, and that energy transfer might occur between Eu3+ and codopant Ln3+ ions, which is suggested as the source of the observed fluorescence enhancement.

Fu, ZhenXing; Zheng, HaiRong; He, EnJie; Gao, Wei; Li, GuiAn

2013-05-01

157

Crystal structure refinements of zircon-type MVO[sub 4] (M = Sc, Y, Ce, Pr, Nd, Tb, Ho, Er, Tm, Yb, Lu)  

SciTech Connect

Improved structural parameters for the lanthanide orthovanadates (including also YVO[sub 4] and ScVO[sub 4] and new results for PrVO[sub 4], TmVO[sub 4], and the LuVO[sub 4] end members) have been determined by employing a full-profile Rietveld structure analysis of neutron powder-diffraction data. High-quality powders of the zircon-type MVO[sub 4] vanadates were prepared by a homogeneous coprecipitation in molten urea. The zircon structure has space group symmetry I4[sub 1]/amd, Z = 4, with 3 atoms occupying the asymmetric unit. In all, 22 parameters were refined with final agreement values of R[sub p] = 0.0313-0.0421, R[sub wp] = 0.0361-0.0511, and G-of-F = 1.210-1.962. The average V-O bond length for all of the MVO[sub 4] samples is 1.709(2) [angstrom], and the V-O distance exhibits a small systematic shortening with decreasing M atom size. The oxygen positional parameters, the cell dimensions, and the M-O distances vary systematically with the metal-ion atomic number. The anisotropic thermal motion of the oxygen atom has the largest amplitude normal to the shared polyhedral edge between the VO[sub 4] tetrahedron and MO[sub 8] bisdisphenoid. Empirical relations are given for the cell dimensions and oxygen atom position as a function of the size of the lanthanide ion which can be used to estimate structural parameters for other zircon-type lanthanide vanadate end-members and vanadate solid solutions.

Chakoumakos, B.C.; Abraham, M.M.; Boatner, L.A. (Oak Ridge National Lab., TN (United States))

1994-03-01

158

Two new ternary lanthanide antimony chalcogenides: Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.68} containing chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anions  

SciTech Connect

Dark red and dark brown crystals of Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 8}Sb{sub 4}Se{sub 11.68}, respectively, were obtained from the reaction of the elements in Sb{sub 2}Q{sub 3} (Q=S, Se) fluxes. Both non-stoichiometric compounds are orthorhombic and crystallize in the same space group Pnnm, with two formula units per unit cell (a=12.446(2), b=5.341(1), c=12.058(2) for sulfide and a=13.126(2), b=5.623(1), c=12.499(2) for the selenide). Their crystal structures are dominated by lanthanide-chalcogenide polyhedra (CN=7 and 8), which share corners, edges, triangular- and square-faces to form a three-dimensional framework embedding antinomy cations. The latter are coordinated by three sulfide anions with 5(1+2+2) secondary contacts forming basically infinite chains running along [0 1 0]. The chalcogens in both compounds form chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anionic units. The optical analysis made on those compounds shows that both are semiconductors with band gap of 1.71 and 1.22 eV for Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.75,} respectively. - Graphical Abstract: The crystal structure of Yb{sub 4}Sb{sub 2}S{sub 11} viewed along the [0 1 0]. Highlights: Black-Right-Pointing-Pointer Lanthanide chalcogenides. Black-Right-Pointing-Pointer Semiconductors. Black-Right-Pointing-Pointer Tunnel structures. Black-Right-Pointing-Pointer Lone-pair effects.

Babo, Jean-Marie [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Albrecht-Schmitt, Thomas E., E-mail: talbrec1@nd.edu [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

2012-03-15

159

Evidence for rattling behavior of the filler atom (L) in the filled skutterudites LT{sub 4}X{sub 12} (L=Ce,Eu,Yb; T=Fe,Ru; X=P,Sb) from EXAFS studies  

SciTech Connect

Extended x-ray absorption fine structure (EXAFS) measurements have been carried out at the L K- or L{sub III}-edges (L=Ce, Eu, and Yb) and T K-edges (T=Fe and Ru) for a series of filled skutterudite materials, LT{sub 4}X{sub 12} (X=P and Sb). The high correlated Debye temperature ({theta}{sub D}{approx}400 K) obtained for the T-X peak indicates that the T{sub 4}X{sub 12} framework is relatively stiff. In contrast, the low Einstein temperature ({theta}{sub E}{approx}100 K) obtained for the L-X or T-L pairs strongly supports the concept of a 'rattling' local mode behavior for the L ions. The analysis also indicates that this rattling frequency is much smaller in the antimonide skutterudites than in the phosphide ones, and smaller in CeOs{sub 4}Sb{sub 12} than in CeFe{sub 4}Sb{sub 12}. Both results indicate that the larger the void within which the Ce atom is located, the lower the rattling frequency. In addition, for some systems in which the signal-to-noise for {sigma}{sup 2}(T) is high, a fit can be made to extract the reduced mass of the rattling atom; in these cases the obtained reduced mass is close to but slightly below that of the rattler atom mass-clear evidence of a localized mode inside a stiff but not rigid cage. Finally, no clear evidence for any off-center displacement of the filler ions was found in these materials.

Cao, D. [Physics Deparment, University of California, Santa Cruz, California 95064 (United States); MS K764, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Bridges, F.; Chesler, P.; Bushart, S. [Physics Deparment, University of California, Santa Cruz, California 95064 (United States); Bauer, E.D.; Maple, M.B. [Department of Physics and Institute of Pure and Applied Physical Science, University of California, San Diego, La Jolla, California 92093 (United States)

2004-09-01

160

Crystallographic phases and transport properties in the superconducting Tm-Ba-Cu-O compound system  

SciTech Connect

The Tm-Ba-Cu-O compound system becomes a superconductor at critical temperature T/sub c/ measured at the midpoint of the resistive transition, of 92 K. From x-ray diffraction techniques, the material seems to be composed of two phases. The dominating (opaque) phase (approx. >94% in weight) is the superconducting TmBa/sub 2/Cu/sub 3/O/sub 6+//sub x/ oxide (isostructural with superconducting oxygen-deficient YBa/sub 2/Cu/sub 3/O/sub 6+//sub x/), which crystallizes in the orthorhombic Pmmm space group with a = 3.819(2), b = 3.889(2), c = 11.669(7)A, and D/sub c/ = 7.12(1) g cm/sup -3/. The other (green) phase is the semiconducting Tm/sub 2/BaCuO/sub 5/ oxide (space group Pbnm or Pbn2/sub 1/; a = 7.079(8), b = 12.09(1), c = 5.633(2)A, and D/sub c/ = 8.53(2)g cm/sup -3/) isostructural with the series of L/sub 2/BaCuO/sub 5/ (L = Y, Sm, Eu, Gd, Dy, Ho, Er, Yb) oxides.

Andreeta, J.P.; Basso, H.C.; Castellano, E.E.; Gallo, J.N.H.; Martin, A.A.; Piro, O.E.

1987-10-01

161

Structural stability of an icosahedral Cd-Yb quasicrystal and its crystalline approximant under high pressure  

NASA Astrophysics Data System (ADS)

Synchrotron x-ray powder diffraction studies on an icosahedral Cd-Yb quasicrystal (iCd-Yb), its crystalline approximant of Cd6Yb (cCd-Yb) and the related Cd25Eu4 (cCd-Eu) material were performed under pressures of up to about 40 GPa at room temperature. The icosahedral lattice of the atomic cluster in iCd-Yb and the bcc lattices in cCd-Yb and cCd-Eu were found to be stable under pressure. Although the Tsai-type atomic cluster can possibly be distorted in various ways, low-symmetry distortion modes do not seem to develop even at high pressure. It is considered that the cluster structure of centrosymmetric dense atomic packing prevented low-symmetry distortions and consequently provided the cluster lattice stability. The bulk moduli were also determined to be B0(iCd-Yb) = 49.2(3) GPa, B0(cCd-Yb) = 46.1(7) GPa and B0(cCd-Eu) = 49.6(3) GPa, which were much lower than the typical reported values for other quasicrystalline alloys.

Watanuki, T.; Sato, T. J.; Tsai, A. P.

2010-03-01

162

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

163

Synthesis and structural characterization of A{sub 3}In{sub 2}Ge{sub 4} and A{sub 5}In{sub 3}Ge{sub 6} (A=Ca, Sr, Eu, Yb)-New intermetallic compounds with complex structures, exhibiting Ge-Ge and In-In bonding  

SciTech Connect

Reported are the synthesis and the structural characterization of four new polar intermetallic phases, which exist only with mixed alkaline-earth and rare-earth metal cations in narrow homogeneity ranges. (Sr{sub 1-x}Ca{sub x}){sub 5}In{sub 3}Ge{sub 6} and (Eu{sub 1-x}Yb{sub x}){sub 5}In{sub 3}Ge{sub 6} (x{approx}0.7) crystallize in the orthorhombic space group Pnma with two formula units per unit cell (own structure type, Pearson symbol oP56). The lattice parameters are as follows: a=13.109(3)-13.266(3) A, b=4.4089(9)-4.4703(12) A, and c=23.316(5)-23.557(6) A. (Sr{sub 1-x}Ca{sub x}){sub 3}In{sub 2}Ge{sub 4} and (Sr{sub 1-x}Yb{sub x}){sub 3}In{sub 2}Ge{sub 4} (x{approx}0.4-0.5) adopt another novel monoclinic structure-type (space group C2/m, Z=4, Pearson symbol mS36) with lattice parameters in the range a=19.978(2)-20.202(2) A, b=4.5287(5)-4.5664(5) A, c=10.3295(12)-10.3447(10) A, and {beta}=98.214(2)-98.470(2){sup o}, depending on the metal cations and their ratio. The polyanionic sub-structures in both cases are based on chains of InGe{sub 4} corner-shared tetrahedra. The A{sub 5}In{sub 3}Ge{sub 6} structure (A=Sr/Ca or Sr/Yb) also features Ge{sub 4} tetramers, and isolated In atoms in nearly square-planar environment, while the A{sub 3}In{sub 2}Ge{sub 4} structure (A=Sr/Ca or Eu/Yb) contains zig-zag chains of In and Ge strings with intricate topology of cis- and trans-bonds. The experimental results have been complemented by tight-binding linear muffin-tin orbital (LMTO) band structure calculations. - Graphical abstract: The anion sub-network of A{sub 5}In{sub 3}Ge{sub 6} is based upon tetrahedral [InGe{sub 4}] chains, Ge{sub 4} tetramers isosteric with 1,3-cis-butadiene, and distorted square-planar [InGe{sub 4}] fragments. The structure of A{sub 3}In{sub 2}Ge{sub 4} is a combination of infinite Ge chains with cis- and trans-bonds in a complex (tttctc){sub n} pattern, tetrahedral [InGe{sub 4}] chains, and In zig-zag chains.

You, Tae-Soo [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen, E-mail: bobev@udel.ed [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)

2010-06-15

164

Investigation of some lanthanide boron, carbon, nitrogen, chalcogen and halogen systems at elevated temperatures. Progress report, February 1, 1959March 31, 1976. [Gd(III)Cl-I-phases; Yb-Br  

Microsoft Academic Search

Research is summarized on thermodynamic properties of borides, ThC, EuC, oxide-carbide phases, YbOC, Eu bromides, vaporization, fluorides, Y chlorides, etc. Preliminary results are given for the preparation of Gd(III) Cl-I phases and the vaporization of YbBr.

Eick

1976-01-01

165

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

166

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

167

Upconversion emission in a carbon-implanted Yb:YAG planar waveguide  

NASA Astrophysics Data System (ADS)

Light confinement and spectroscopic properties of a Yb:YAG planar waveguide fabricated by ion implantation were investigated. Under 970 nm excitation, cooperative upconversion and near infrared luminescence were observed. The interaction between Yb3+ ion pairs was responsible for the appearance of a blue-green band centered at 514 nm. However, several more bands in the blue, green and red regions were detected and are related to Er3+ and Tm3+ ion impurities. The upconversion emission of such ion impurities is explained in terms of an efficient energy transfer from Yb3+ to Er3+ and Tm3+ due to high Yb3+ concentration. The stimulated emission cross section for the 2F5/2?2F7/2 transition of Yb3+ was 1.9×10-20 cm2. The fluorescence lifetime of the 2F5/2 level and that of the blue-green band were 1.28 ms and 593 ?s respectively. The self-convolution of IR emission was calculated and the result shows that the main peak is centered at 514 nm. Such self-convolution and the fact that the blue-green band lifetime is half the IR lifetime are good evidences for cooperative emission of Yb3+ ion pairs.

Vázquez, G. V.; Desirena, H.; De la Rosa, E.; Flores-Romero, E.; Márquez, H.; Rickards, J.; Trejo-Luna, R.

2012-11-01

168

K-shell absorption jump factors and jump ratios in elements between Tm (Z = 69) and Os (Z = 76) derived from new mass attenuation coefficient measurements  

NASA Astrophysics Data System (ADS)

The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm2O3, Yb2O3 compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56 77 keV, were done in a transmission geometry utilizing the K?1, K?2, K?1 and K?2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV ?-photons from an 57Co annular source and detected by an Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values. The measured values of Tm, Yb, Lu, Hf, Ta, W, Re and Os are reported here for the first time.

Kaya, Necati; T?ra?o?lu, Engin; Apayd?n, Gökhan; Ayl?kc?, Volkan; Cengiz, Erhan

2007-08-01

169

Electronic Configuration of Yb Compounds  

SciTech Connect

The total energy differences between divalent and trivalent configurations of Yb ions in a number of Yb compounds are studied. Two different band theoretical methods, which differ in the treatment of the localized f electrons, are used. The results show that in all Yb compounds the valence energy differences are equal to the energy needed to localize an f electron. These valence energy differences correlate with the number of f electrons hybridizing with the conduction bands in the trivalent configuration. For divalent YbS, the pressure induced f -electron delocalization implies an intermediate valency, as also indicated by experiment. {copyright} {ital 1999} {ital The American Physical Society }

Temmerman, W.M.; Szotek, Z. [Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, Cheshire (United Kingdom); Svane, A. [Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Strange, P. [Physics Department, Keele University, Keele, Staffordshire, ST5 5BG (United Kingdom); Winter, H. [INFP, Forschungszentrum Karlsruhe GmbH, Postfach 3640, D-76021 Karlsruhe (Germany); Delin, A.; Johansson, B.; Eriksson, O.; Fast, L. [Condensed Matter Theory Group, Department of Physics, University of Uppsala, Box 530, 75121 Uppsala (Sweden); Wills, J.M. [Center of Materials Science and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)

1999-11-01

170

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

171

Yb:S-FAP Lasers.  

National Technical Information Service (NTIS)

It has recently been reported that several high power, diode-pumped laser systems have been developed based on crystals of Yb:S-FAP(Yb(sup 3+):Sr(sub 5)(PO(sub 4)(sub 3)F). The Mercury Laser, at Lawrence Livermore National Laboratory, is the most prominen...

K. I. Schaffers

2004-01-01

172

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

173

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

174

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

175

Optical study of Yb(3+)/Yb(2+) conversion in CaF(2) crystals.  

PubMed

Yb(3+) ions with various site symmetries have been observed in the absorption and emission spectra of Yb(3+):CaF(2) crystals, both ?-irradiated and annealed in hydrogen. The absorption intensity value is found to be much higher for the ?-irradiated crystal and strongly dependent on the gamma dose. The UV absorption spectra of ?-irradiated and H(2)-annealed CaF(2):5 at.% Yb(3+) crystals are quite similar. Yb(2+) absorption bands are observed at 360, 315, 271, 260, 227 and 214 nm, which are called A, B, C, D, F and G bands, respectively. For ?-irradiated CaF(2):30 at.% Yb(3+), an additional band at 234 nm can be seen. It is suggested that only a negligible amount of Yb(3+) ions are converted into Yb(2+) under the ?-irradiation. The presence of Yb(2+) is confirmed by the 565 and 540 nm luminescence under 357 nm excitation. It is also suggested that the excitation in the A, C, D and F absorption bands of Yb(2+) gives rise to photo-ionization of Yb(2+) ions and electrons in the conduction band to form the excited Yb(3+) ions which emit IR Yb(3+) luminescence.The UV absorption and emission spectra obtained for ?-irradiated and H(2)-annealed crystals have different structures. This suggests that different mechanisms are responsible for the creation of Yb(2+) ions. ?-irradiation favours Yb(2+) isolated centres by reduction of Yb(3+) ions located at Ca(2+) lattice sites, whereas annealing in hydrogen favours Yb(2+) centres neighbouring Yb(3+) ions when a Yb(3+) ion pair captures a Compton electron. Also, ?-irradiation does not change the position of Yb(3+) ions converted into Yb(2+) in the CaF(2) lattice. In the case of H(2) annealing, a Yb(3+) ion converted to Yb(2+) is shifted to the Ca(2+) position in the lattice. PMID:21690695

Kaczmarek, S?awomir M; Tsuboi, Taiju; Ito, Masahiko; Boulon, Georges; Leniec, Grzegorz

2005-06-10

176

High power Yb:KGW and Yb:KYW thin disk laser operation  

Microsoft Academic Search

Summary form only given. The Yb3+-doped potassium tungstates KY(WO4)2 (KYW) and KGd(WO4) 2 (KGW) are for several reasons of great interest for diode-pumped solid state lasers. Compared with Yb:YAG, they have a smaller quantum defect of only ~4% and higher absorption and emission cross sections. Furthermore Yb:KGW and Yb:KYW have a broad emission bandwidth, comparable to that of Yb:glass, which

S. Erhard; J. Gao; A. Giesen; K. Contag; A. A. Lagatsky; A. Abdolvand; N. V. Kuleshov; J. Aus der Au; G. J. Spuhler; F. Brunner; R. Paschotta; U. Keller

2001-01-01

177

The tmRNA website.  

PubMed

tmRNA (10Sa RNA) has a central role in trans -translation, in which a peptide tag encoded in tmRNA is added to the abnormally short protein product of a broken mRNA, as a signal for proteolysis of the entire tagged protein. The tmRNA website was established in 1997 as a resource for phylogenetic considerations of tmRNA structure and function. Since then, three partial tmRNA sequences have been completed, and sequences from 13 more species have been identified. Forty-six species from 10 bacterial phyla and chloroplasts are now represented in the database. Provisional sequence alignments and predicted proteolysis tag sequences are provided, as well as a literature review and a guide to searching for new tmRNA sequences. The tmRNA website is accessible via WWW at a new URL: http://sunflower.bio.indiana.edu/kwilliam/tmRNA /home.html PMID:9847167

Williams, K P

1999-01-01

178

GEOMAG[TM] Paradoxes  

ERIC Educational Resources Information Center

|As often happens, a lot of physics can come out of a toy. What we found interesting is the observation of the magnetic field produced by different configurations built with GEOMAG[TM]. This toy provides small magnetic bars and steel spheres to play with. Amusing 3-D structures can be built; nevertheless, this possibility is not so obvious.…

Defrancesco, Silvia; Logiurato, Fabrizio; Karwasz, Grzegorz

2007-01-01

179

Physics of YbBiPt  

NASA Astrophysics Data System (ADS)

YbBiPt has a low temperature linear specific heat coefficient of 8 J/mol Yb K2 and a small specific heat anomaly at 0.4 K. We discuss new experiments on the specific heat of diluted YbBiPt, magnetic field dependent effects and electrical resistivity in pure YbBiPt. We argue that in this material the Kondo and crystal field energy scales are small and of comparable magnitude, placing YbBiPt in the same class as many uranium heavy electron compounds.

Thompson, J. D.; Canfield, P. C.; Lacerda, A.; Hundley, M. F.; Fisk, Z.; Ott, H.-R.; Felder, E.; Chernikov, M.; Maple, M. B.; Visani, P.; Seaman, C. L.; Lopez de La Torre, M. A.; Aeppli, G.

1993-05-01

180

Lifetime measurement in ^170Yb  

NASA Astrophysics Data System (ADS)

The nature of the low lying K^?=0^+ excitations in deformed nuclei have recently been subject of intense discussion. In this context we present results from a Coulomb excitation experiment on ^170Yb using a 70MeV ^16O beam on a gold backed, 1.5 mg/cm^2 thick ^170Yb target. The beam was delivered by the ESTU tandem accelerator of WNSL at Yale University. Gamma rays were detected by the YRAST Ball array in coincidence with back-scattered ^16O particles, which were detected in an array of 8 solar cells. Lineshapes were observed for several transitions from collective states in ^170Yb and the lifetimes for those states were extracted using a standard DSAM analysis. The results will be presented together with a short introduction to the solar cell array at Yale (SCARY) that was used to make angular selection of the excited ^170Yb nuclei. This work is supported by the US-DOE under grant numbers DE-FG02-91ER-40609 and DE-FG02-88ER-40417.

Wang, Z.; Krücken, R.; Beausang, C. W.; Casten, R. F.; Cooper, J. R.; Cederkäll, J.; Caprio, M.; Novak, J. R.; Zamfir, N. V.; Barton, C.

1999-10-01

181

Structural and physical properties of the new intermetallic compound Yb{sub 3}Pd{sub 2}Sn{sub 2}  

SciTech Connect

The crystal structure of the ternary intermetallic compound Yb{sub 3}Pd{sub 2}Sn{sub 2} has been determined ab initio from powder X-ray diffraction data. The compound crystallizes as a new structure type in the orthorhombic space group Pbcm and lattice constants a=0.58262(3), b=1.68393(8), c=1.38735(7) nm. Yb{sub 3}Pd{sub 2}Sn{sub 2} is composed of a complex {sub {infinity}}[Pd{sub 2}Sn{sub 2}]{sup {delta}-} polyanionic network in which the Yb ions are embedded. A comparison between this structure and those of Eu{sub 3}Pd{sub 2}Sn{sub 2} and Ca{sub 3}Pd{sub 2}Sn{sub 2}, other novel polar intermetallic compounds, was made. DC susceptibility and {sup 170}Yb Moessbauer spectroscopic measurements indicate a close-to divalent Yb behavior. Moreover, a hybridization between 4f and conduction electrons is suggested by electronic structure calculations and heat capacity measurements. - Graphical Abstract: Polyanionic networks for Yb{sub 3}Pd{sub 2}Sn{sub 2} and Eu{sub 3}Pd{sub 2}Sn{sub 2}. Highlights: > We determined ab initio the crystal structure of the novel ternary Yb{sub 3}Pd{sub 2}Sn{sub 2} stannide. > This structure has been compared with those of other polar 3:2:2 stannides discovered in this work. > Measurements of physical properties on Yb{sub 3}Pd{sub 2}Sn{sub 2} point to a close-to-divalent Yb ion. > Electron structure calculation and heat capacity indicate some hybridization between 4f and conduction electrons.

Solokha, P. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Curlik, I. [Institute of Experimental Physics, Watsonova 47, SK 043 53 Kosice (Slovakia); Giovannini, M., E-mail: giovam@chimica.unige.it [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Lee-Hone, N.R. [Physics Department and Centre for the Physics of Materials, McGill University, Montreal, Canada H3A 2T8 (Canada); Reiffers, M. [Institute of Experimental Physics, Watsonova 47, SK 043 53 Kosice (Slovakia); Faculty of Sciences, University of Presov, 17. Novembra 1, SK 080 78 Presov (Slovakia); Ryan, D.H. [Physics Department and Centre for the Physics of Materials, McGill University, Montreal, H3A 2T8 (Canada); Saccone, A. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy)

2011-09-15

182

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

2013-02-27

183

Yb3+-doped Gd3Ga5O12 garnet single crystals grown by the micro-pulling down technique for laser application. Part 2: Concentration quenching analysis and laser optimization  

NASA Astrophysics Data System (ADS)

This article is following the first part published recently in this journal [S. Chénais, F. Druon, F. Balembois, P. Georges, A. Brenier, G. Boulon, Opt. Mater. 22 (2003) 99]. Yb3+ concentration dependence of the 2F5/2 excited level experimental decay time in GGG laser crystal was analyzed in order to understand involved concentration quenching mechanisms. Under Yb3+ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to rare earth impurities (Er3+, Tm3+) have been observed in visible region and interpreted by a limited diffusion process within the Yb3+ doping ion subsystem towards impurities. OH- quenching centres, Yb2+ ions and color centres may also be involved in such processes but Yb3+ pairs do not seem efficient. Main parameters useful for the optimization of laser potentiality have also been given from a new model which has been published recently.

Guyot, Y.; Canibano, H.; Goutaudier, C.; Novoselov, A.; Yoshikawa, A.; Fukuda, T.; Boulon, G.

2006-01-01

184

Synchroton Soft X-ray Absorption Studies of YbFe1-xMnxO3 (0.0 <= x <= 1.0) Perovskites  

NASA Astrophysics Data System (ADS)

This work aims to correlate the interplay between structure-bonding (O2p-TM3d) and magnetic properties (TM 3d) in YbFe1-xMnxO3 (0.0 <= x <= 1.0) perovskites which are synthesized by the solid state reaction method. We have investigated by XAS the O2p and the magnetic TM3d unoccupied states of YbFe1-xMnxO3 (0<=x<=1). We find that increasing Mn doping promotes the creation of new states at the O2p band, it also induces a shifts towards lower energies of the O K pre-edge (with reference to the O2p-TM3d hybridization) and changes the spectral distribution in the region of TM 4s, p -- O 2p- Yb 5d hybridization. These changes are most marked for x 0.2. A correlated effect with Mn doping is observed in the Fe L2,3 spectra where again new electronic states and systematic changes are observed x 0.2. This is in contrast with Mn L2,3 spectra, where all the spectra are very similar except for x=0.2. Thus, we provide a comprehensive picture of the electronic structure evolution in the conduction band in these materials as a function of the Mn content.

Olalde-Velasco, P.; Yang, W. L.; Hernandez, C.; Chavira, E.; Rosales, I.; Tejada, A.; Huerta, L.; Jimenez-Mier, J.; Marinero, E. E.

2013-03-01

185

Yb-Bi pulsed fiber lasers  

Microsoft Academic Search

A new type of pulsed fiber laser is suggested and developed--Yb-Bi lasers. In such lasers the Yb fiber laser is Q-switched by use of a saturable absorber, a Bi-doped fiber placed in its own resonator, and pulsed lasing is obtained in both fiber lasers. Continous-wave diode-clad pumping of the Yb-Bi lasers at a 975 nm wavelength with power up to

V. V. Dvoyrin; V. M. Mashinsky; E. M. Dianov

2007-01-01

186

Probing dual mode emission of Eu3+ in garnet phosphor  

NASA Astrophysics Data System (ADS)

Eu3+ doped and Eu3+, Yb3+ co-doped Gd3Ga5O12 phosphors have been developed by facile solid state reaction method which can be easily scaled-up in large quantity. The synthesis has been optimized to get a single phase material at 1300 °C. The phase and crystal parameters have been analyzed by using X-ray diffraction measurement. Photoluminescence excitation (monitored for the 5D0 --> 7F1 transition of Eu3+) depicts that the active ion (Eu3+) can be excited through direct excitation into 4f band of Eu3+, through charge transfer band (Eu3+-O2-) excitation and also through the excitation into 8S7/2 --> 6IJ intra f-f transition of Gd3+ ion, which significantly all together cover a broad excitation region in 200-420 nm. In addition, in the presence of Yb3+ ions, the emission is also achieved by near infrared excitation (976 nm), through a typical upconversion (UC) process. Thus, the material efficiently behaves as a dual mode emitting phosphor (emission is achieved both through normal fluorescence and through UC process). The conversion efficiency of silicon solar cells is only 15% of terrestrial solar energy for 200-400 nm region and also the sub-band gap energy (in infrared region) is lost as heat; therefore, this kind of dual mode phosphors may be used to overcome the above mentioned incomplete utilization of the solar spectrum and can open realm of new possibilities for energy harvesting.

Singh, S. K.; Gi Lee, Dong; Soo Yi, Soung; Jang, Kiwan; Shin, Dong-Soo; Hyun Jeong, Jung

2013-05-01

187

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

2013-07-09

188

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

189

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

190

EPR study of Yb-doped irradiated glasses  

NASA Astrophysics Data System (ADS)

Yb3+ reduction under ? and ? irradiation has been studied in aluminoborosilicate glasses by EPR spectroscopy. From the Yb3+ EPR line variation, we demonstrate that more than one Yb3+ sites coexist in the pristine Yb-doped glasses. Reduction of Yb3+ into Yb2+ is observed for all integrated doses and Yb doping contents. For doses higher than 108 Gy, an Yb3+ ion environment change occurs, this change is correlated with a stabilization of the reduced Yb2+ state. The paramagnetic defect concentration displays a linear variation as a function of the logarithm of the dose. The glass doping with Yb2O3 leads to a substantial decrease of the defect concentration as well as a modification in the relative proportion of the defects produced. In particular, Yb doping tends to increase the relative content of Oxy defects.

Ollier, N.; Planchais, R.; Boizot, B.

2008-06-01

191

Nonpareil Yb Behavior in YbMn6Ge6-xSnx  

NASA Astrophysics Data System (ADS)

We investigate the temperature dependence of the Yb valence in YbMn6Ge1.8Sn4.2 and YbMn6Ge1.6Sn4.4 using resonant inelastic x-ray scattering experiments. Yb is found to be in an intermediate valent state in the whole investigated temperature range (10–450 K). We thus prove that the unusually high magnetic ordering temperature of Yb (˜60 and 90 K for x=4.2 and 4.4, respectively) involves an intermediate valent Yb, an unprecedentedly observed phenomenon. Further, an anomalous increase in the Yb valence is observed upon cooling. A scenario is proposed to explain this unusual behavior. It is based on the presence of magnetically ordered Mn moments and on an Anderson Hamiltonian with a Zeeman term modeling the magnetic interactions.

Mazet, T.; Malterre, D.; François, M.; Dallera, C.; Grioni, M.; Monaco, G.

2013-08-01

192

Nonpareil Yb Behavior in YbMn_{6}Ge_{6-x}Sn_{x}.  

PubMed

We investigate the temperature dependence of the Yb valence in YbMn_{6}Ge_{1.8}Sn_{4.2} and YbMn_{6}Ge_{1.6}Sn_{4.4} using resonant inelastic x-ray scattering experiments. Yb is found to be in an intermediate valent state in the whole investigated temperature range (10-450 K). We thus prove that the unusually high magnetic ordering temperature of Yb (?60 and 90 K for x=4.2 and 4.4, respectively) involves an intermediate valent Yb, an unprecedentedly observed phenomenon. Further, an anomalous increase in the Yb valence is observed upon cooling. A scenario is proposed to explain this unusual behavior. It is based on the presence of magnetically ordered Mn moments and on an Anderson Hamiltonian with a Zeeman term modeling the magnetic interactions. PMID:24033054

Mazet, T; Malterre, D; François, M; Dallera, C; Grioni, M; Monaco, G

2013-08-28

193

Virally encoded 7TM receptors  

Microsoft Academic Search

A number of herpes- and poxviruses encode 7TM G-protein coupled receptors most of which clearly are derived from their host chemokine system as well as induce high expression of certain 7TM receptors in the infected cells. The receptors appear to be exploited by the virus for either immune evasion, cellular reprogramming, tissue targeting or for cell entry. Through their efficient

Mette M Rosenkilde; Maria Waldhoer; Hans R Lüttichau; Thue W Schwartz

2001-01-01

194

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.

195

Yb-doped chirped pulse amplification system  

NASA Astrophysics Data System (ADS)

A very compact, all diode pumped chirped pulse amplification system was developed based on Yb-doped gain materials. A passively mode-locked Yb:KYW oscillator in combination with a photonic crystal fiber was used to seed two different regenerative amplifiers. Energies up to 10mJ at 20Hz were obtained for cryo-cooled Yb:YLF and 6.5mJ between 10Hz and 30Hz for Yb:YAG at cryogenic temperatures also. For Yb:YAG it was possible to blue shift the spectrum of the oscillator to match the wavelength of the amplifier and the seed beam without using the non-linear fiber. The entire system (oscillator-stretcher-amplifier) has a footprint of less than 2m^2. After compression it should be possible to obtain amplified pulse duration of <8ps.

Furch, Federico; Reagan, Brendan; Luther, Bradley; Rocca, Jorge

2007-10-01

196

Different evolution of the intrinsic gap in strongly correlated SmB6 in contrast to YbB12  

NASA Astrophysics Data System (ADS)

Dependence of the spectral functions near the Fermi level on temperature and rare-earth atom doping was studied in detail for strongly correlated alloys Sm1-xEuxB6 and Yb1-xLuxB12 by photoelectron spectroscopy at ˜8000 eV as well as at 7 and 8.4 eV. It was found that the 4f lattice coherence and intrinsic gap are robust for Sm1-xEuxB6 at least up to the Eu substitution of x = 0.15 while both collapse by Lu substitution already at x = 0.125 for Yb1-xLuxB12. As for the temperature dependence of the spectral shapes near the Fermi level at low temperatures, rather contrasting results were observed between YbB12 and SmB6. Although the gap shape does not change below 15 K for YbB12 with the characteristic temperature T* of 80 K, the spectral shape of SmB6 with a T* of 140 K shows that the peak beyond the gap is further increased below 15 K. The temperature dependence of the spectra near the intrinsic gap is clearly different between SmB6 and YbB12, although both materials have so far been categorized in the same kind of strongly correlated semiconductor. The possibility of the surface contribution is discussed for SmB6.

Yamaguchi, J.; Sekiyama, A.; Kimura, M. Y.; Sugiyama, H.; Tomida, Y.; Funabashi, G.; Komori, S.; Balashov, T.; Wulfhekel, W.; Ito, T.; Kimura, S.; Higashiya, A.; Tamasaku, K.; Yabashi, M.; Ishikawa, T.; Yeo, S.; Lee, S.-I.; Iga, F.; Takabatake, T.; Suga, S.

2013-04-01

197

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

198

High-pressure synthesis, crystal structure, and structural relationship of the first ytterbium fluoride borate Yb5(BO3)2F9  

NASA Astrophysics Data System (ADS)

Yb5(BO3)2F9 was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 °C, representing the first known ytterbium fluoride borate. The compound exhibits isolated BO3-groups next to ytterbium cations and fluoride anions, showing a structure closely related to the other known rare-earth fluoride borates RE3(BO3)2F3 (RE=Sm, Eu, Gd) and Gd2(BO3)F3. Monoclinic Yb5(BO3)2F9 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 ?=100.63(3)° (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 RE3(BO3)2F3 (RE=Sm, Eu, Gd) and Gd2(BO3)F3, Yb5(BO3)2F9 can be described via alternating layers with the formal compositions “YbBO3” and “YbF3” in the bc-plane.

Haberer, Almut; Huppertz, Hubert

2009-04-01

199

Magnetism and heavy fermions in YbRhSn and YbPtSn  

SciTech Connect

Isostructural YbRhSn and YbPtSn were studied by specific heat, electrical resistivity, and magnetoresistance. Both compounds order antiferromagnetically below 2 and 3.5 K, respectively. Above 4 K, they display a number of remarkable similarities including Kondo-like resistivity and large negative magnetoresistance. Scaling analysis of this magnetoresistance shows that it is due to the suppression of Kondo scattering in YbRhSn but has a ferromagnetic spin fluctuation character in YbPtSn. The heavy fermion state was confirmed in YbRhSn by low temperature specific heat measurements yielding {gamma} of about 1200 mJ/K2 mol. {gamma} for YbPtSn is of order 100 mJ/K2 mol only. (c) 2000 American Institute of Physics.

Andraka, Bohdan [Department of Physics, University of Florida, P.O. Box 118440, Gainesville, Florida 32611-8440 (United States); Pietri, Richard [Department of Physics, University of Florida, P.O. Box 118440, Gainesville, Florida 32611-8440 (United States); Kaczorowski, Dariusz [W.Trzebiatowski Institute for Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroclaw 2, (Poland); Leithe-Jasper, A. [Institut fuer Physikalische Chemie der Universitaet Wien, Waehringerstrasse 42, A-1090 Vienna, (Austria); Rogl, P. [Institut fuer Physikalische Chemie der Universitaet Wien, Waehringerstrasse 42, A-1090 Vienna, (Austria)

2000-05-01

200

Collapse dynamics of a {sup 176}Yb-{sup 174}Yb Bose-Einstein condensate  

SciTech Connect

In this paper, we present a theoretical study of a two-component Bose-Einstein condensate composed of ytterbium (Yb) isotopes in a three-dimensional anisotropic harmonic potential. The condensate consists of a mixture of {sup 176}Yb atoms which have a negative s-wave scattering length and {sup 174}Yb atoms having a positive s-wave scattering length. We study the ground-state as well as dynamic properties of this two-component condensate. Due to the attractive interactions between {sup 176}Yb atoms, the condensate of {sup 176}Yb undergoes a collapse when the particle number exceeds a critical value. The critical number and the collapse dynamics are modified due to the presence of {sup 174}Yb atoms. We use coupled two-component Gross-Pitaevskii equations to study the collapse dynamics. The theoretical results obtained are in reasonable agreement with the experimental results of Fukuhara et al. [Phys. Rev. A 79, 021601(R) (2009)].

Chaudhary, G. K.; Ramakumar, R. [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

2010-06-15

201

Luminescence of Yb2+, Yb3+ co-doped silica glass for white light source  

NASA Astrophysics Data System (ADS)

Yb2+, Yb3+ co-doped silica glasses were prepared by solid state reaction under vacuum condition for the first time. The luminescence properties of Yb2+-doped silica glass were investigated. There are four strong absorption bands in the Ultraviolet (UV) light region due to the 4f14-4f135d1 transition of the Yb2+ ions. The main emission wavelength of the Yb2+-doped silica glass was around 530 nm by the excited wavelength of 398 nm. The full width at half maximum (FWHM) of the excitation and emission bands were 137 nm, 165 nm respectively. The results suggest the Yb2+-doped silica glasses may be the potential medium for white light sources based on near UV LED chip.

Xia, Changming; Zhou, Guiyao; Han, Ying; Zhao, Xingtao; Hou, Lantian

2012-03-01

202

Single Crystal Growth of a New YB 50Family Compound: YB 44Si 1.0  

Microsoft Academic Search

Single crystals of a new yttrium borosilicide of YB44Si1.0have been grown by the floating zone method using a xenon lamp image furnace. X-ray powder diffraction, precession photography, and chemical analyses showed that the crystal obtained is a new YB50family yttrium borosilicide which has a composition of YB44.4Si1.04in the middle part of the crystal and an orthorhombic crystal structure with space

Takaho Tanaka; Shigeru Okada; Yoshio Ishizawa

1997-01-01

203

Influence of Yb and Yb2O3 on the properties of InP layers  

Microsoft Academic Search

The influence of Yb and Yb2O3 addition on the properties of InP epitaxial layers is reported. We concentrated on the investigation of gettering and\\/or doping efficiency of Yb added in various forms. Layers prepared by Liquid Phase Epitaxy were examined by using SEM, SIMS, low temperature PL spectroscopy, C-V and temperature dependent Hall measurements. The efficient gettering was confirmed for

O. Prochazkova; J. Grym; J. Zavadil; J. Lorineik; K. Zdansky

2008-01-01

204

Isotope-selective trapping of doubly charged Yb ions  

SciTech Connect

We report isotope-selective loading and trapping of doubly ionized ytterbium into an rf quadrupole trap. Isotopically pure clouds of {sup 174}Yb{sup +} ions were first loaded into the rf trap via a multistage photoionization process. The Yb{sup 2+} ions were then produced by electron impact ionization of the trapped Yb{sup +} ions. The Yb{sup 2+} ions were subsequently detected by rf excitation of their secular motion in the trap, which led to sympathetic heating and changes in the fluorescence of the laser-cooled Yb{sup +} ions. The presence of doubly charged Yb ions was further verified by the appearance of a dark band in the center of Yb{sup +} ion cloud after electron impact ionization. We discuss the possible formation of Yb{sup 2+}H and similar compounds and the schemes for the direct optical detection of the Yb{sup 2+} ions.

Schauer, M. M.; Danielson, J. R.; Feldbaum, D.; Rahaman, M. S.; Wang, L.-B.; Zhang, J.; Zhao, X.; Torgerson, J. R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2010-12-15

205

Low temperature paramagnetic scattering from YbInAu2 and YbAl3  

NASA Astrophysics Data System (ADS)

We have investigated paramagnetic scattering from YbInAu2 and compare it with that from YbAl3 which has closely comparable low temperature bulk susceptibility ?(0) as well as linear specific heat coefficient ?. Whereas YbAl3 shows a `gap-like' spectral response at low temperatures (5 K) with an energy gap of ~ 32 meV, the low temperature magnetic response of YbInAu2 shows the more common inelastic Lorentzian form centred on ~ 38 meV (width ~ 25 meV), which can also be closely represented by the Kuramoto-Müller Hartmann spectral function yielding a Kondo energy of ~ 35 meV. The integrated spectral intensity (calibrated relative to the bulk susceptibility) suggests a partial 4f occupancy of ~ 0.7 (+/- 0.05), closely similar to that found for YbAl3. The presence of optic phonons at energies close to the characteristic Kondo energy in YbAl3 and their apparent absence at similar energies in YbInAu2 points to coupling with phonons as a possible mechanism for the marked `distortion' of the spectral shape to its `gap-like' form in YbAl3.

Murani, A. P.; Pierre, J.

1995-02-01

206

Low temperature magnetism in YbPtBi by {sup 170}Yb Moessbauer spectroscopy  

SciTech Connect

The authors report on {sup 170}Yb Moessbauer spectroscopy data in the cubic fcc alloy YbPtBi, in the temperature range 0.06--30 K. The zero field spectra show a two component structure above 1.5 K, which can be analyzed as due to 85% of Yb{sup 3+} ions at a site with cubic symmetry and 15% at a site with non-cubic symmetry. Below 0.3 K, the spectra are resolved and can also be interpreted in terms of two sites, but with a dominant non-cubic site ({approximately} 60%) with Yb ions bearing small magnetic moments. The spectra with a large applied magnetic field give information on the Yb{sup 3+} C.E.F. level scheme and on the exchange interaction. The relation of the Moessbauer data with the results of {micro}SR measurements is discussed.

Le Bras, G.; Bonville, P.; Hodges, J.A.; Imbert, P. [C.E. Saclay, Gif-sur-Yvette (France); Canfield, P.C. [Ames Lab., IA (United States)

1994-05-24

207

Lattice dynamics in the thermoelectric Zintl compound Yb[subscript 14]MnSb[subscript 11  

SciTech Connect

The density of phonon states in the thermoelectric material Yb{sub 14}MnSb{sub 11} 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 Yb{sub 14}MnSb{sub 11} 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 Eu{sub 14}MnSb{sub 11} compound and of the thermoelectric Zintl phase Zn{sub 4}Sb{sub 3} in order to compare with related thermodynamic properties of Yb{sub 14}MnSb{sub 11} 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. (DESY); (UCD); (Julich); (ILL); (ESRF); (ETH Zurich)

2012-04-02

208

EU Regulatory Perspectives  

Center for Drug Evaluation (CDER)

Text Version... Quality systems have a legal footing in EU GMP ... Concept Paper published April 2009 ... Some terminology and concepts in ICH Q10 different from ... More results from www.fda.gov/downloads/drugs/developmentapprovalprocess

209

Yb:S-FAP laser performance  

NASA Astrophysics Data System (ADS)

We have demonstrated the highest long-pulse efficiency and highest Q-switched energy reported to date for a Yb:S-FAP laser. THe Yb:S-FAP laser was pumped with a flashlamp pumped, free-running Cr:LiSAF laser. Threshold pump energy was extremely low, typically 30 mJ. Maximum output energy was 370 mJ at 1.047 micrometers with 650 mJ of pump incident on the Yb:S-FAP crystal. We obtained total optical-to-optical conversion efficiency of up to 57 percent in the long pulse mode. This is the highest conversion efficiency ever reported for this material in high energy, pulsed mode. Three samples of Yb:S-FAP of differing dimensions, doping, and crystal quality were tested. Two of the Yb:S-FAP crystals showing crystal defects experienced bulk damage during Q-switched mode of operation. The remaining crystal had the lowest dopant concentration of all the crystals, limiting the stored energy. Up to 65 mJ of output was obtained in this high-quality crystal, the highest ever reported in Q-switched mode with this laser material. Conversion efficiency at this energy level was 11.8 percent. However, the maximum efficiency obtained was 16.3 percent before pump bleaching effects started to occur due to low dopant concentration in this crystal sample.

Pierce, Jeffrey W.; Mead, Roy D.

1997-03-01

210

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

211

Luminescence in BaSO4:Eu  

Microsoft Academic Search

Photoluminescence and thermoluminescence in BaSO4:Eu is reported. In earlier works, divalent Eu has been studied in BaSO4. In the present work Eu was incorporated as in predominantly Eu or Eu form. It is shown that RE ? RE conversion or RE ? RE conversion is not an integral part of gamma induced TL. Eu ? Eu conversion, on the other

M. S. Atone; S. J. Dhoble; S. V. Moharil; S. M. Dhopte; P. L. Muthal; V. K. Kondawar

1993-01-01

212

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

Microsoft Academic Search

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 Delta 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

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

2011-01-01

213

Blue up-conversion emission in Yb and Tm-codoped potassium yttrium tungstate  

Microsoft Academic Search

The spectroscopic characteristics of potassium yttrium tungstate crystal (KYW), codoped with ytterbium and thulium ions, have been investigated from the point of view of up-conversion blue lasing from 1G4 multiplet. An overall 3H6 multiplet splitting of ~530 cm-1 for the trivalent thulium ion in the KYW host was obtained. A decay time of ~112 mus for the 1G4-->3H6 blue luminescence

A. N. Kuzmin; A. V. Kachynski; P. N. Prasad; A. A. Demidovich; L. E. Batay; A. Bednarkiewicz; W. Strek; A. N. Titov

2004-01-01

214

Yb-Bi pulsed fiber lasers  

NASA Astrophysics Data System (ADS)

A new type of pulsed fiber laser is suggested and developed--Yb-Bi lasers. In such lasers the Yb fiber laser is Q-switched by use of a saturable absorber, a Bi-doped fiber placed in its own resonator, and pulsed lasing is obtained in both fiber lasers. Continous-wave diode-clad pumping of the Yb-Bi lasers at a 975 nm wavelength with power up to 16.5 W results in pulsed laser action in a spectral diapason of 1050-1200 nm with a maximum pulse energy of up to 100 ?J, an average power up to 7.5 W, and a repetition rate up to 100 kHz.

Dvoyrin, V. V.; Mashinsky, V. M.; Dianov, E. M.

2007-03-01

215

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

216

Superfluorescence from Yb- and Yb Er-doped phosphotellurite glass fibres  

NASA Astrophysics Data System (ADS)

Short length, air-clad, multimode fibres were fabricated using high concentration Yb- and Yb Er-doped phosphotellurite glass. Superfluorescent light sources are obtained by optically pumping the fibres using a 980 nm laser diode. Ytterbium-doped fibre showed amplified spontaneous emission (ASE) in the 1000 1100 nm wavelength region, whereas Yb Er-codoped fibre in both 1000 1100 nm (due to Yb3+ ions) and 1450 1650 nm (due to Er3+ ions) wavelength regions. The ASE spectra from the fibres are compared for different fibre lengths and pump powers. The observed change in the ASE spectral shape and the shift in peak wavelength with the length of the optical fibre is discussed.

Nandi, P.; Jose, G.

2008-10-01

217

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

218

Phase diagram for 1\\/2 Yb2O3-BaO-CuO  

Microsoft Academic Search

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

D. E. Peterson; E. Oniyama; P. G. Wahlbeck; J. Y. Coulter; E. J. Peterson

1997-01-01

219

Mössbauer spectra of Eu(III) and Gd(III) complexes of phosphine oxides with chelating perchlorate  

NASA Astrophysics Data System (ADS)

The reaction of Ln(ClO4)3· nH2O with triphenylphosphine oxide (TPPO) in methanol has led to the formation of [Ln(ClO4)2(tppo)4]ClO4·MeOH (Ln = Nd, Eu, Gd, Dy, Yb), in which the perchlorate anion acts as a symmetric bidentate. The emission spectra of Eu(III)-TPPO complexes, showing enhancement in the intensity due to the phenyl group, indicate an isotropic electron distribution for the nitrato complex [Eu(NO3)3(tppo)2(EtOH)]. 151Eu and 155Gd Mössbauer spectra of the TPPO complexes also lead to the same conclusion.

Takahashi, Masashi; Hirai, Yuya

2012-03-01

220

EU Agro Biogas Project  

Microsoft Academic Search

EU-AGRO-BIOGAS is a European Biogas initiative to improve the yield of agricultural biogas plants in Europe, to optimise biogas technology and processes and to improve the efficiency in all parts of the production chain from feedstock to biogas utilisation. Leading European research institutions and universities are cooperating with key industry partners in order to work towards sustainable biogas production in

T. Amon; H. Mayr; M. Eder; P. Hobbs; S. Rao Ravella; U. Roth; A. Niebaum; H. Doehler; P. Weiland; E. Abdoun; A. Moser; M. Lyson; M. Heiermann; M. Plöchl; J. Budde; A. Schattauer; T. Suarez; H. Möller; A. Ward; F. Hillen; P. Sulima; A. Oniszk-Polplawska; P. Krampe; Z. Pastorek; J. Kara; J. Mazancova; Dooren van H. J. C; C. Wim; F. Gioelli; P. Balsari

2009-01-01

221

EU Agro Biogas Project  

Microsoft Academic Search

EU-AGRO-BIOGAS is a European Biogas initiative to improve the yield of agricultural biogas plants in Europe, to optimise biogas technology and processes and to improve the efficiency in all parts of the production chain from feedstock to biogas utilisation. Leading European research institutions and universities are cooperating with key industry partners in order to work towards a sustainable Europe. Fourteen

T. Amon; H. Mayr; M. Eder; P. Hobbs; S. Rao Ravella; U. Roth; A. Niebaum; H. Doehler; P. Weiland; E. Abdoun; A. Moser; M. Lyson; M. Heiermann; M. Plöchl; J. Budde; A. Schattauer; T. Suarez; H. Möller; A. Ward; F. Hillen; P. Sulima; A. Oniszk-Polplawska; P. Krampe; Z. Pastorek; J. Kara; J. Mazancova; Dooren van H. J. C; C. Wim; F. Gioelli; P. Balsari

2009-01-01

222

Making EU Network Markets Competitive  

Microsoft Academic Search

Since the late 1980s the EU has made great strides in the liberalization of network markets. This article assumes a horizontal perspective, juxtaposing different network markets while focusing solely on the rules and policies at EU level. A six-step checklist is applied to facilitate a comparative analysis of EU regulatory liberalization in gas, electricity, telecoms, postal services, and rail and

Jacques Pelkmans

2001-01-01

223

Upconversion blue emission dependence on the pump mechanism for Tm3+-heavy-doped NaY(WO4)2 crystal  

NASA Astrophysics Data System (ADS)

Upconversion blue emissions of Tm3+-ion-heavy-doped NaY(WO4)2 crystals are investigated with three different near-infrared pump mechanisms. The dependence of upconversion efficiency on the pump mechanism is analyzed from the scope of the concentration quenching effect. Three cross-relaxation processes, {}^3H_5+{}^1G_4to{}^3H_6+{}^1D_2, {}^1G_4+{}^3H_6to{}^3F_4+{}^3F_3, and {}^1G_4+{}^3H_6to{}^3F_3+{}^3F_4, which influence the upconversion dominantly in the Tm3+-heavy-doped system, are demonstrated theoretically and experimentally. The results indicate that Yb3+ ions can weaken the concentration quenching effect of Tm3+ ions significantly so that the blue emission efficiency can be enhanced by one order of magnitude. At the same time, the wavelength of the pump source also has considerable influence on both the population of some crucial energy levels and the upconversion mechanism. Experiments show that the upconversion blue emission in Tm3+/Yb3+ co-doped NaY(WO4)2 crystal under 980-nm laser diode excitation is the most intensive of these three different near-infrared pump mechanisms. The conclusions are confirmed by spectra measurements and calculations of Judd Ofelt theory and Miyakawa Dexter theory.

Song, F.; Han, L.; Zou, C.; Su, J.; Zhang, K.; Yan, L.; Tian, J.

2007-03-01

224

Isotope shift measurements and charge radii of152 158Yb  

NASA Astrophysics Data System (ADS)

Isotope shifts have been measured for the neutron deficient even Yb isotopes up to the neutron shell closure at N=82. The isotope shifts were measured using the 556-nm atomic resonance transition from the1 S 0 ground state to the3 P 1 level. The heavier isotopes of Yb have been investigated by Buchinger et al./1/. The change in ( r 2) observed for Yb isotopes with N=82 90 has considerably different behavior than for the lighter rare earths.

Sprouse, G. D.; Das, J.; Lauritsen, T.; Schecker, J.; Berger, A.; Billowes, J.; Holbrow, C. H.; Kim, W.; Xu, F.

1990-08-01

225

Excited states in {sup 155}Yb and  

SciTech Connect

The 270-MeV {sup 58}Ni+{sup 102}Pd reaction was used for the first recoil-decay tagging measurement with Gammasphere coupled to the Fragment Mass Analyzer at Argonne National Laboratory. Level structures of {sup 155}Yb, {sup 156}Lu, and {sup 157}Lu, as well as the excited states associated with the 25/2{sup -} isomer in {sup 155}Lu, are identified for the first time. The systematical behavior of the energy levels is compared with that of neighboring isotones and isotopes. The attractive interaction between h{sub 11/2} protons and h{sub 9/2} neutrons plays an important role in the structure of {sup 155}Yb and {sup 155,156}Lu.

Ding, K. Y.; Cizewski, J. A.; Seweryniak, D.; Amro, H.; Carpenter, M. P.; Davids, C. N.; Fotiades, N.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J. (and others)

2001-09-01

226

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

227

Magnetically Tunable Feshbach Resonances in Ultracold Li-Yb Mixtures  

NASA Astrophysics Data System (ADS)

We investigate the possibility of forming Li+Yb ultracold molecules by magnetoassociation in mixtures of ultracold atoms. We find that magnetically tunable Feshbach resonances exist, but are extremely narrow for even-mass ytterbium isotopes, which all have zero spin. For odd-mass Yb isotopes, however, there is a new mechanism due to hyperfine coupling between the electron spin and the Yb nuclear magnetic moment. This mechanism produces Feshbach resonances for fermionic Yb isotopes that can be more than 2 orders of magnitude larger than for the bosonic counterparts.

Brue, Daniel A.; Hutson, Jeremy M.

2012-01-01

228

Crystal growth and properties of Yb:FAP laser crystal  

NASA Astrophysics Data System (ADS)

A large and transparent Yb:FAP crystal with dimensions up to ?30 mm×85 mm has been grown by the Czochralski method. The preparation of the raw material has been investigated. X-ray power diffraction studies of Yb:FAP crystal confirm that the as-grown crystal is isostructural with the FAP crystal. The crystalline quality has been studied using X-ray rocking curve analysis. The segregation coefficient of Yb3+ in the Yb:FAP crystal has been also determined. Linear thermal expansion coefficients in [0 0 1] and [1 0 0] directions have been measured in the 30 800 °C temperature range.

Song, Pingxin; Zhao, Zhiwei; Xu, Xiaodong; Deng, Peizhen; Xu, Jun

2005-04-01

229

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

230

K=0 Rotational Bands in 174Yb  

Microsoft Academic Search

The gamma deexcitation of three excited K=0 rotational bands has been studied following population in the 173Yb(n,gamma) reaction at resonant neutron energies of 4.53 and 17.7 eV. The gamma rays were detected in singles and coincidence with Ge(Li) detectors. Analysis was also made of the primary radiation. The decay properties of these bands exhibit strong deviations from the Alaga ratios.

R. F. Casten; D. Breitig; W. R. Kane; S. F. Mughabghab

1973-01-01

231

Charge transfer luminescence of Yb 3+  

Microsoft Academic Search

A systematic study of charge transfer (CT) luminescence from Yb3+ is presented. CT luminescence was observed in LiYF4 (?7eV), aluminates, phosphates, oxides (?4eV) and oxysulfides (?3eV). In all cases the CT emission bands are broad and the Stokes shifts are large, ranging from 7000cm?1 in oxysulfides and LiYF4 and up to 17000cm?1 in aluminates. The influence of the size of

L. van Pieterson; M. Heeroma; E. de Heer; A. Meijerink

2000-01-01

232

Scaling of Yb-Fiber Frequency Combs  

NASA Astrophysics Data System (ADS)

Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E.; Hartl, Ingmar

2010-06-01

233

Cooperative energy transfer in Tb3+/Yb3+- and Nd3+/Yb3+/Tb3+-codoped oxyfluoride glasses  

NASA Astrophysics Data System (ADS)

This paper reports on cooperative energy transfer and upconversion luminescence properties of Tb3+/Yb3+- and Nd3+/Yb3+/Tb3+-codoped oxyfluoride glasses. Upon excitation with a 980 nm laser diode, an intense green upconversion luminescence along with weak ultraviolet (UV)-visible emissions has been observed in Yb3+/Tb3+-codoped oxyfluoride glasses. Power dependence of UV-visible upconversion luminescence intensity has been examined, revealing that a cooperative energy transfer mechanism from Yb3+ ions is responsible for the excitation of Tb3+ ions. Meanwhile, it is noticed that Tb3+ upconversion emission bands have also been clearly detected at 487, 542, 587 and 620 nm in Nd3+/Yb3+/Tb3+-codoped oxyfluoride glasses upon excitation with a 808 nm laser diode. The quadratic dependence of the upconversion luminescence on the pump-laser power indicates two-photon process for the population of Tb3+:5D4 state via Nd3+?Yb3+?Tb3+ energy transfer. However, no emission has been observed in the oxyfluoride glasses codoped with Yb3+/Tb3+ or Nd3+/Tb3+, respectively, upon excited at a 808 nm laser diode. A proposed upconversion mechanism involving energy transfer from Nd3+ to Yb3+, and then a cooperative energy transfer process from two excited Yb3+ to Tb3+ has been presented.

Zhang, W. J.; Chen, Q. J.; Qian, Q.; Zhang, Q. Y.; Jiang, Z. H.

2010-02-01

234

Avalanche upconversion in Tm:YALO3  

Microsoft Academic Search

The sudden appearance of upconversion fluorescence and resonant increasing absorption above a threshold intensity in Tm:YALO3 at room temperature is reported. These effects are shown to arise from nonlinear, cooperative, excited-state dynamics. Comparison with quantum theory reveals essential roles both for pairwise cross relaxation and excitation migration among Tm impurity ions.

H. Ni; S. C. Rand

1991-01-01

235

Magnetic Ordering Phenomena in TmS.  

National Technical Information Service (NTIS)

Neutron diffraction data have been obtained from powder and single crystal specimens of TmS at temperatures ranging from room temperature to 1.7 K and in applied magnetic fields up to 42.8 kOe. In zero field TmS undergoes a transition, at about 8.9 K, to ...

W. C. Koehler R. M. Moon F. Holtzberg

1978-01-01

236

Radiotherapy and Antiangiogenic TM in Lung Cancer  

Microsoft Academic Search

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 combi- nation of cytotoxic radiotherapy (RT ) and antiangio- genic TM could target both the existing tumor and the tumor microvasculature in

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

2002-01-01

237

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

2013-02-05

238

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

239

Selectivity of glassy type mixed zirconium-titanium phosphate toward rare earth metal ions  

Microsoft Academic Search

The selectivity of glass type mixed Zr+Ti phosphates with various Ti contents has been investigated toward rare earth metal ions. The kd values were determined by radiotracer technique both in HCl and HNO3 solutions of various concentrations. At room temperature and at pH=4 the following selectivity orders were found: Yb>TmEu>Sm>La (HCl) and Eu>La>Sm>Yb>Tm (HNO3).

S. K. Shakshooki; A. Dhair; L. Szirtes; Yu. V. Yakovlev

1991-01-01

240

Optical spectroscopy and energy transfer in Tm3+-doped metaphosphate laser glasses  

NASA Astrophysics Data System (ADS)

Thulium-doped metaphosphate glasses with four concentrations (0.01, 0.1, 1.0 and 2.0 mol%) of Tm3+ have been prepared and investigated by Raman, absorption and photoluminescence spectral studies. The phonon sideband spectrum has been measured for 1.0 mol% Eu3+-doped metaphosphate glass of the same composition and compared with the Raman spectrum. From vibronic spectra, various bands associated with different structural groups have been identified and assigned. Absorption band positions have been used to simulate the complete energy level diagram for the Tm3+ ion using the model Hamiltonian. Judd-Ofelt parameters have been determined from the absorption bands. Using these parameters, transition probabilities, excited state lifetimes and transition branching ratios have been evaluated. The emission and decay curves of the 1D2 level have been measured for all four glass samples both at RT and 15 K. Lifetimes show a strong quenching for Tm3+ concentrations higher than 0.1 mol%. Fluorescence decay curves of the 1D2 level have been well fitted to the Inokuti-Hirayama model for S = 6, suggesting that the mechanism for energy transfer between Tm3+ ions is of dipole-dipole type.

Babu, P.; Seo, Hyo Jin; Jang, Kyoung Hyuk; Balakrishnaiah, R.; Jayasankar, C. K.; Joshi, A. S.

2005-08-01

241

Structure induced Yb valence changes in the solid solution Yb(x)Ca(1-x)C2.  

PubMed

The solid solution Yb(x)Ca(1-x)C2 (0 ? x ? 1) was synthesized by reaction of the elements at 1323 K. The crystal structures within this solid solution, as elucidated from synchrotron powder diffraction data, depend on x and exhibit some interesting features that point to a structure dependent valence state of Yb. Compounds with x ? 0.75 crystallize in the tetragonal CaC2 type structure (I4/mmm, Z = 2) and obey Vegard's law; for x ? 0.75 the monoclinic ThC2 type structure (C2/c, Z = 4) is found, which coexists with the monoclinic CaC2-III type structure (C2/m, Z = 4) for x ? 0.25. The monoclinic modifications show a strong deviation from Vegard's law. Their unit cell volumes are remarkably larger than expected for a typical Vegard system. HERFD-XANES spectroscopic investigations reveal that different Yb valence states are responsible for the observed volume anomalies. While all tetragonal compounds contain mixed-valent Yb with ?75% Yb(3+) (similar to pure YbC2), all monoclinic modifications contain exclusively Yb(2+). Therefore, Yb(x)Ca(1-x)C2 is a very rare example of a Yb containing compound showing a strong structure dependence of the Yb valence state. Moreover, temperature dependent synchrotron powder diffraction, neutron TOF powder diffraction, and HERFD-XANES spectroscopy experiments reveal significant Yb valence changes in some compounds of the Yb(x)Ca(1-x)C2 series that are induced by temperature dependent phase transitions. Transitions from the tetragonal CaC2 type structure to the monoclinic ThC2 or the cubic CaC2-IV type structure (Fm3m, Z = 4) are accompanied by drastic changes of the mean Yb valence from ?2.70 to 2.0 in compounds with x = 0.75 and x = 0.91. Finally, the determination of lattice strain arising inside the modifications with ordered dumbbells (ThC2 and CaC2 type structures) by DSC measurements corroborated our results concerning the close relationship between crystal structure and Yb valence in the solid solution Yb(x)Ca(1-x)C2. PMID:23721507

Link, Pascal; Glatzel, Pieter; Kvashnina, Kristina; Trots, Dmytro M; Smith, Ronald I; Ruschewitz, Uwe

2013-05-30

242

[Separation with ion exchange fiber column and determination of La, Nd, Eu and Gd in high purity ytterbium oxide by ICP-AES].  

PubMed

In the present paper, trace La, Nd, Eu and Gd were separated and enriched with strong acid ion exchange fiber column from high purity Yb2 O3, and then determined by Optima 5 300 DV ICP-AES. The ion exchange fiber's breakthrough capacity for Yb was 134 mg x g(-1). The separation condition using 4.0 g fiber column was that after the test solution (pH = 3.0) was fed into the ion exchange fiber column at 1.0 mL x min(-1), the column was pre--leached by dilute nitric acid (pH = 3.00) of 80 mL at 1.5 mL x min(-1) at first, and then was eluted by 0.01 mol x L(-1) ammonium EDTA (pH = 5.00) at the same flow rate. The results showed that 10 mg Yb could reach the baseline separation with 0.100 microg of the four rare earth impurities, and after 100 mg Yb in feed solution had been separated, only 0.017 1 microg x mL(-1) Yb remained in the impurities enriched effluent. When the concentration of Yb2 O3 is less than 100 microg x mL(-1) (87.8 microg x mL(-1) Yb), the matrix interference from Yb on with determination of La, Nd, Eu and Gd can be neglected. The enrichment factors were 3.68 x 10(5) for La2 O3, 4.20 x 10(5) for Nds O3, 3.82 x 10(5) for Eu2 O3, and 4.01 x 10(5) for Gd2 O3, and the detection limits of the method were 0.005 0, 0.014, 0.001 8 and 0.008 2 pg x mL(-1) for La2 O3, Nd2 O3, Eu2 O3 and Gd2 O3 respectively. The proposed method was applied to the analysis of 99.99% Yb2 O3 with RSD (%, n = 5) of 6.2, 5.9, 7.3 and 2.5 for La2 O3, Nd2 O3, Eu2 O3 and Gd2 O3 respectively, and the average recoveries of standard addition were 94.2%, 107%, 97.8% and 102% for La2 O3, Nd2 O3, Eu2 O3 and Gd2 O3 respectively. The calibration curve did not need matrix matching with Yb, and the analysis period was within 4 hour. PMID:20384159

Gong, Qi; Chen, Jie; Ji, Ri-Wen; Pan, Xue-Zhen; Wu, Juan

2010-02-01

243

Response of Kondo lattice systems to pressure. [YbAgCu/sub 4/; YbCu/sub 2/Si/sub 2/; YbRh/sub 2/Si/sub 2/  

SciTech Connect

Yb-based Kondo lattice systems (YbAgCu/sub 4/, YbCu/sub 2/Si/sub 2/, YbRh/sub 2/Si/sub 2/) represent an interesting class of materials in which it is possible to study systematically the development of heavy electron behavior through the application of pressure. Certainly, additional experiments are required to determine to what extent Yb compounds are mirror images of their Ce counterparts. Finally, pressure reveals the presence of competing interactions for which a simple model exists that qualitatively accounts for the pressure response observed in a large number of Ce, U and Yb-based Kondo lattice systems.

Thompson, J.D.; Borges, H.A.; Fisk, Z.; Horn, S.; Parks, R.D.; Wells, G.L.

1987-01-01

244

The IBM-1 Study for 170-174Yb Isotopes  

NASA Astrophysics Data System (ADS)

The electromagnetic properties of even-even 170-174Yb isotopes with neutron number 100 ? N ? 104 are studied within the framework of the first version of the interacting Boson Model (IBM-1). The B(E2) and Q(2+) values of the above nuclei are calculated. Numerical results for 170-174Yb are compared with previous experimental and theoretical values.

Maraþ, Ýsmail

1997-12-01

245

Transparent Ceramic Yb3+:Lu2O3 Materials.  

National Technical Information Service (NTIS)

Conventional ceramic processing uses a liquid phase co-precipitation method to produce transparent Yb-doped Lu2O3 materials. In this work, fully transparent Yb-doped Lu2O3 ceramics were produced by a simple solid-state reaction method for the first time. ...

A. Ikesue

2012-01-01

246

Transport and mechanical properties of Yb-filled skutterudites  

Microsoft Academic Search

A series of Yb-filled skutterudites were produced and powder samples consolidated using spark plasma sintering (SPS). The effect of different heating cycles on the resulting transport properties of the consolidated samples was explored. Specifically, the effect of sample uniformity on the electrical and thermal transport properties was explored. In addition to the optimal Yb-filling fraction, other factors, such as heating

J. R. Salvador; J. Yang; X. Shi; H. Wang; A. A. Wereszczak; H. Kong; C. Uher

2009-01-01

247

Er and Yb Isotope Fractionation in Planetary Material  

NASA Astrophysics Data System (ADS)

We present an investigation of Er and Yb isotopes in Earth, meteorites, and the Moon by MC-ICP-MS. The main results concern the Yb redox state, condensation of the Moon from the impact vapor, and neutron adsorption by the lunar surface.

Albalat, E.; Telouk, P.; Albarede, F.

2012-03-01

248

Effect of Bi ion on Eu 2+  ? Eu 3+ conversion in CaF 2 :Eu phosphors for RPL dosimetry  

Microsoft Academic Search

UV photo-excited Eu2+ and Eu3+ luminescence from CaF2:Eu and CaF2:Eu, Bi phosphors were investigated. The effect of gamma exposure followed by temperature effect shows conversion mechanism\\u000a between Eu2+ ? Eu3+ ion in CaF2:Eu and CaF2:Eu, Bi phosphors which were studied for RPL dosimetry. The photoluminescence and X-ray diffraction characterization are reported\\u000a in this article.

S. J. DhobleI; I. M. Nagpure; N. S. Dhoble; Pablo Molina

249

Dynamics of Tm-Ho energy transfer and deactivation of the 3F4 low level of thulium in fluorozirconate glasses  

NASA Astrophysics Data System (ADS)

The mechanism involved in the Tm3+ (3F4)-->Ho3+ (5I7) energy transfer and Tm3+ (3H4, 3H6)-->Tm3+ (3F4, 3F4) cross relaxation as a function of the donor and acceptor concentrations was investigated in Tm-Ho-codoped fluorozirconate glasses. The experimental transfer rates were determined for the Tm-->Ho energy transfer from the best fit of the acceptor luminescence decay using an expression which takes into account the Inokuti-Hirayama model and localized donor-to-acceptor interaction solution. The original acceptor solution derived from the Inokuti-Hirayama model fits well the acceptor luminescence transient only for low-concentrated systems. The results showed that a fast excitation diffusion that occurs in a very short time (t<Yb:Er:ZBLAN. The fast excitation diffusion effect was observed to dominate both the Tm-->Tm cross relaxation and Tm-->Ho energy transfer ions from 3H4 and 3F4 thulium states, respectively.

da Vila, L. D.; Gomes, L.; Tarelho, L. V. G.; Ribeiro, S. J. L.; Messaddeq, Y.

2004-05-01

250

Effect of Yb3+ Concentrations on the Upconversion Luminescence Properties of ZrO2:Er3+,Yb3+ Phosphors  

NASA Astrophysics Data System (ADS)

ZrO2:Er3+ and ZrO2:Er3+,Yb3+ phosphors were synthesized via a solvothermal reaction method. For low concentrations of Yb3+, the crystalline structure changed from the tetragonal to monoclinic phase as sintering temperature increased. As the Yb3+ concentration increased to a value above 0.05 mol, ZrO2 phosphors displayed a very stable tetragonal phase. The green and red upconversion emissions of ZrO2:Er3+,Yb3+ phosphors were measured under the excitation with a 975 nm continuous wave diode laser, and the pump power dependence of upconversion intensity was investigated. As the Yb3+ concentration increased from 0 to 0.05 mol, the red upconversion emission intensity increased more rapidly than the green emission intensity. This is attributed to the energy transfer (4I11/2?4I15/2:4I_{13/2}?4F9/2) between Er3+ ions and the energy back transfer [4S3/2:4I_{13/2(Er3+)}?2F7/2:2F_{5/2(Yb3+)}] between the Er3+ and Yb3+ ions. In this case, the pump power dependence of red emission intensity changed from quadratic to linear as Yb3+ concentration increased.

Noh, Hyeon Mi; Yang, Hyun Kyoung; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun; Choi, Haeyoung; Kim, Jung Hwan

2013-01-01

251

Magnetism and Superconductivity in RuM1.5Ce0.5Sr2Cu2O10 (M=Eu and Y)  

NASA Astrophysics Data System (ADS)

RuY1.5Ce0.5Sr2Cu2O10, is not superconducting (SC) and orders magnetically at TM=152 K. The Ru moment at 5 K is 0.75?B. Ferromagnetic hysteresis loops are observed below Tirr=100 K. At 100 K, the remanent magnetization (Mrem) and the coercive field (HC) become zero. Surprisingly, at TirrTM a reappearance of antiferromagnetic (AFM) hysteresis loops are observed with a peak at 120 K for both Mrem and HC. The paramagnetic constants are: Peff=2.06?B (greater than the 1.73?B expected for low spin Ru5+) and ?=136 K which agrees well with TM. Substitution of Zn (2.5% atm.) for Cu in RuEu1.5Ce0.5 Sr2Cu2O10 (TC=38 K), suppresses TC but does not affect the magnetic features such as: TM and Tirr, Mrem and HC. This indicates that both SC and magnetic states are practically decoupled. We argue that the magnetic structure of this system becomes (i) AFM ordered at TM. (ii) Due to the tilting of the RuO6 octahedra away from the crystallographic c-axis, at Tirr<TM, weak-ferromagnetic (W-FM) order is induced by the canting of the Ru moments. (iii) At TC (TM/TC~4), the specific materials (M=Eu, Gd) become SC. Below TC, both SC and W-FM states coexist.

Felner, I.; Galstyan, E.; Awana, V. P. S.; Takayama-Muromachi, E.

2004-08-01

252

151Eu Mössbauer study of luminescent Y2O3:Eu3 + core-shell nanoparticles  

NASA Astrophysics Data System (ADS)

151Eu Mössbauer spectroscopy was applied to distinguish among different Eu microenvironments and phases in spherical Y2O3:Eu3 + and core-shell Y2O3@Eu3 + phosphor nanoparticles prepared by using homogeneous precipitation method. 151Eu isomer shift revealed that Eu atoms exist only in oxidation state Eu3 + in all spherical and core-shell phosphors. Significant differences have been found between the Mössbauer parameters (isomer shift, principal component of EFG and linewidth) characteristic of spherical Y2O3:Eu3 + and core-shell Y2O3@Eu3 + phosphor nanoparticles. The Mössbauer parameters of spherical Y2O3:Eu3 + were associated with Eu substituting Y in the Y2O3, while Mössbauer parameters of core-shell Y2O3@Eu3 + phosphor were attributed to Eu being in the Eu2O3 shell, proving the structural model and the successful preparation of these phosphors.

Kuzmann, E.; Vértes, A.; Bohus, G.; Hornok, V.; Oszkó, A.; Dékány, I.

2013-04-01

253

Double layer formation in Mg–TM switchable mirrors (TM: Ni, Co, Fe)  

Microsoft Academic Search

The optical properties of Mg–TM (TM: Ni, Co, Fe; Mg:TM ? 2) thin films during hydrogenation are investigated using reflection and transmission measurements. Mg–Ni and Mg–Co show an unusual behavior upon exposure to hydrogen. The nucleation of the hydride starts at the film substrate interface and not – as intuitively expected – at the Pd covered top side of the

W. Lohstroh; R. J. Westerwaal; A. C. Lokhorst; J. L. M. van Mechelen; B. Dam; R. P. Griessen

2005-01-01

254

Direct elucidation of the effect of building defects on the physical properties of alpha-TmAlB4; An AlB2-type analogous ``tiling'' compound  

NASA Astrophysics Data System (ADS)

With a counterintuitive approach to crystal growth, single crystals of ?-TmAlB4 were successfully grown, which were indicated from transmission electron microscopy (TEM) and x-ray diffraction (XRD) measurements and analysis to be virtually free from the ubiquitous building defects, and their properties investigated. Recent developments in rare earth aluminoboride compounds with two-dimensional boron layers have attracted interest due to the heavy fermion superconductivity in ?-YbAlB4, multiple anomalies manifesting below the Néel temperatures in ?-TmAlB4 attributed to intrinsic building defects, and field stable state in Tm2AlB6. The physical properties of the obtained ?-TmAlB4 crystals show a striking difference from the properties of conventional ?-TmAlB4 crystals containing building defects. TN = 6.8 K is revealed to be higher than the 5.8 K formerly thought, and the multiple anomalies below TN are replaced by a sharp ?-like peak in the specific heat C. The large effect of the building defects on the physical properties could be directly confirmed, and strikingly it is shown how the large peak structure in the specific heat of the high quality sample could be destroyed by the presence of a small amount (one or two percent) of building defects.

Mori, T.; Kuzmych-Ianchuk, I.; Yubuta, K.; Shishido, T.; Okada, S.; Kudou, K.; Grin, Y.

2012-04-01

255

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

256

Weak ferromagnetism in single crystalline YbB6-?  

NASA Astrophysics Data System (ADS)

We present a study of magnetization and transport properties of single crystals of YbB6 and YbB6+/-? (?=0.3 as a nominal value). The YbB6-? crystal revealed a weak ferromagnetism, manifested by hysteresis loop in M(H) at room temperature with a saturation magnetic moment of 1.5×10-4 ?B/f.u. and the ferromagnetic transition temperature higher than T=300 K, whereas YbB6 and YbB6+? crystals revealed diamagnetism and paramagnetism, respectively. It was found that the bulk magnetic property of YbB6+/-? crystals is intrinsically diamagnetic and that the magnetism, ferromagnetism, or paramagnetism is a surface effect. Based on x-ray photoelectron spectroscopy and electron probe microanalyzer measurements, we believed that the extraneous magnetic impurities, such as Fe and Ni, are not the origin of the ferromagnetism or paramagnetism. While we observed from electrical resistivity and Hall resistivity that the off stoichiometry in YbB6+/-? causes carrier doping effect, it is not clear at present what surface state creates the magnetic signals.

Kim, J. Y.; Sung, N. H.; Cho, B. K.

2007-05-01

257

Photoionization of Yb(NH3)n complexes.  

PubMed

The ionization energies of complexes between a rare-earth metal (Yb) and ammonia were measured for the first time. Using photoionization mass spectrometry under molecular-beam conditions, the adiabatic ionization energies of Yb(NH3)n were determined for n=1-10. Ab initio calculations were also carried out in support of this work and were found to be in excellent agreement with experiment. The combined findings from theory and experiment are consistent with formation of "interior" complexes in which the Yb atom is embedded within a shell of NH3 molecules, rather than sitting on the surface of an (NH3)n cluster. The calculations also suggest that Yb can accommodate up to eight NH3 molecules in its first solvation shell before steric repulsion makes occupancy of the second solvation shell more favourable energetically. The experimental ionization data are consistent with this prediction, as demonstrated by below-trend adiabatic ionization energies for the n=9 and 10 complexes. The ionization energies of Yb(NH3)n complexes closely follow those for complexes of alkali metal atoms with NH3, which suggests that a valence electron will eventually detach from the Yb atom to form a solvated electron in Yb(NH3)n when n is sufficiently large. PMID:23090714

Guttridge, Matthew J; Don, Sadna H; Ellis, Andrew M

2012-10-22

258

Scintillation properties of Yb3+-doped YAG transparent ceramics  

NASA Astrophysics Data System (ADS)

We investigated scintillation properties of Yb3+-doped Y3A5O12 (YAG) transparent ceramics with different dopant concentrations. The transparency of both 0.3% and 15% Yb3+-doped exceeded 70% in the wavelength range 300-800 nm, and two kinds of absorption bands due to charge transfer (CT) transition and 4f-4f forbidden transition of Yb3+ were observed around 200-250 nm and 900 nm, respectively. Ultraviolet luminescence caused by the CT transition between Yb3+ and O2- was observed under ?-ray excitation from 241Am sealed source. The scintillation decay times were determined to be about 2.2 ns (Yb 0.3%) and 1.4 ns (Yb 15%) using the streak camera system equipped with pulsed X-ray source. From 241Am alpha-ray-excited pulse height spectra, the relative scintillation light yield of 0.3% and 15% Yb3+-doped ceramics was 7% and 10% compared with that of BGO commercial scintillator.

Fujimoto, Yutaka; Yanagida, Takayuki; Wakahara, Shingo; Yagi, Hideki; Yanagidani, Takagimi; Kurosawa, Shunsuke; Yoshikawa, Akira

2013-02-01

259

The OpenTM Transactional Application Programming Interface  

Microsoft Academic Search

Transactional Memory (TM) simplifies parallel pro- gramming by supporting atomic and isolated execution of user-identified tasks. To date, TM programming has re- quired the use of libraries that make it difficult to achieve scalable performance with code that is easy to develop and maintain. For TM programming to become practical, it is important to integrate TM into familiar, high-level environ-

Woongki Baek; Chi Cao Minh; Martin Trautmann; Christos Kozyrakis; Kunle Olukotun

2007-01-01

260

The OpenTM Transactional Application Programming Interface  

Microsoft Academic Search

Transactional Memory (TM) simplifies parallel programming by supporting atomic and isolated execution of user-identified tasks. To date, TM programming has re quired the use of libraries that make it difficult to achieve scalable performance with code that is easy to develop and maintain. For TM programming to become practical, it is important to integrate TM into familiar, high-level environments for

Woongki Baek; Chi Cao Minh; Martin Trautmann; Christos Kozyrakis; Kunle Olukotun

2007-01-01

261

Optimization of Yb-Er microchip laser parameters  

NASA Astrophysics Data System (ADS)

Output parameters of microchip lasers based on Yb:Er co-doped phosphate glasses have been numerically calculated using a simplified 4-level model in order to optimize the Yb and Er concentrations and active medium length. It was shown that active media with Yb concentration ~2·1027 m-3 and length of the order of 1 mm were most appropriate to obtain the practically maximum slope efficiency and minimum threshold power. Simulation results indicated that the Er concentration could be much lower than those currently used in practice. The obtained results were in good agreement with available experimental data.

Burov, L. I.; Krylova, L. G.

2012-07-01

262

Fabrication and laser properties of transparent Yb:YAG ceramics  

NASA Astrophysics Data System (ADS)

High optical quality transparent Yb:YAG laser ceramics have been successfully fabricated by a vacuum reactive sintering method. Commercial Al2O3 powder and co-precipitated Y2O3 and Yb2O3 powders were used as the raw materials. In-line transmittances at 1300 nm and 400 nm were measured to be 83.6% and 81.8% respectively for a 3 mm thick mirror polished Yb:YAG ceramics sample. Continuous wave (CW) lasing at the wavelength of 1030 nm was achieved when pumped by a 940 nm fiber coupled laser diode. A slope efficiency as high as 62.7% was obtained.

Luo, Dewei; Zhang, Jian; Xu, Changwen; Qin, Xianpeng; Tang, Dingyuan; Ma, Jan

2012-04-01

263

Er and Yb isotope fractionation in planetary materials  

NASA Astrophysics Data System (ADS)

Terrestrial planets are depleted in volatile elements relative to solar abundances. Little is known, however, about volatility at the high temperatures relevant to asteroidal collisions and to the giant lunar impact. Although refractory rare-earth elements have overall similar crystallochemical properties, some differ in their temperatures of condensation from the nebular gas. This is the case for Yb, which condenses at ˜1490K and in the vapor is mostly in elemental form. By contrast, Er, largely present as ErO, condenses at ˜1660K. We analyzed the Er and Yb isotopic compositions in 33 terrestrial basalts, garnets, different classes of chondrites and achondrites, and lunar samples by MC-ICP-MS. The range of mass-dependent isotope fractionation is larger for Yb (0.43‰ per amu) than Er (0.23‰) isotopes. For terrestrial rocks, a positive correlation between ?Yb and La/Yb suggests that the isotopic differences between Er and Yb can be accounted for by the presence of small fractions of Yb2+. Yb is isotopically heavy in kimberlite and light in garnets. Ytterbium behaves similarly to Fe, with Yb3+ being more incompatible than the much less abundant Yb2+. In addition, the coexistence of divalent and trivalent sites in the garnet structure and the preference of heavy isotopes for stable bonds makes Yb in garnet isotopically light. The deficit of heavy Yb isotopes in lunar basaltic samples relative to the Earth, chondrites, and eucrites provides new evidence that the Moon formed by the condensation of silicate vapor in the aftermath of the giant lunar impact. Separation of vapor from melt and of heavy from light isotopes is first expected during the adiabatic expansion of the initial vapor plume. Subsequently, friction between melt and gas tends to further enrich the Moon feeding zone in silicate vapor to compensate the inward migration of melt out of the pre-lunar disk. A major consequence of interpreting the present lunar data by vapor/melt segregation is that the relative abundances of refractory elements in the Moon are unlikely to be chondrite-like or even Earth-like. Erbium isotope ratios in lunar samples reflect the capture of neutrons produced by galactic cosmic rays. The first resonance of 167Er for neutron capture will help cover an energy range poorly covered by other nuclides.

Albalat, Emmanuelle; Telouk, Philippe; Albarède, Francis

2012-11-01

264

Divalent Yb Cations and Distorted, Inequivalently-Charged C_60 Anions in Yb_2.75C_60  

NASA Astrophysics Data System (ADS)

Near-edge x-ray absorption measurements from Yb_2.75C_60 establish that the Yb cations are exclusively divalent, meaning that the average negative formal charge of the C_60 anions is 5.5. Extended x-ray absorption fine structure and Raman measurements also reveal that the C_60 anions are distorted in shape, despite their well ordered local structure around Yb. Together, these findings are used to show that the charge transferred from Yb to C_60 is both anisotropically distributed on the anions and inequivalently partitioned among them within the unit cell. The inhomogeneous charge distribution stems from the partially covalent interactions between Yb and C_60, a situation similar to (albeit weaker than) that between Pt and C_60 in [(C_6H_5)_3P]_2Pt-C_60.The inequivalent anionic charge states stem from the three crystallographically distinct types of C_60 anions surrounded by 8, 10, or 12 Yb cations, a situation similar to (and more pronounced than) the inequivalent O anions in YBa_2Cu_3O_7. Comparisons are made with analogous metal-doped fullerides and organometallic compounds, which provide new insight into the distinctive structure of Yb_2.75C_60 and its unique distribution of anion charge. More generally, our results are shown to have implications to all other alkaline- and rare-earth (i.e., divalent-metal) fullerides.

Citrin, P. H.; Schuppler, S.; Ozdas, E.; Kortan, A. R.; Lyons, K. B.

1997-03-01

265

Formation of Eu 2+ and Eu 3+ centers in synthesis of CaF 2 :Eu luminophores  

Microsoft Academic Search

We have studied the effect of CaF2:Eu luminophore synthesis methods on the charge state of europium. We have shown that Eu3+ predominates over Eu2+ in samples obtained by coprecipitation of europium with calcium fluoride, and the ratio Eu3+\\/Eu2+ grows as the total amount of europium increases. Partial charge conversion of the europium occurs during calcination of the\\u000a samples, due to

M. I. Danilkin; A. P. Belousov; S. O. Klimonskii; V. D. Kuznetsov; A. L. Lust; V. N. Nikiforov; L. N. Paama; I. Kh. Pammo; V. O. Seeman

2007-01-01

266

Formation of Eu2+ and Eu3+ centers in synthesis of CaF2:Eu luminophores  

Microsoft Academic Search

We have studied the effect of CaF2:Eu luminophore synthesis methods on the charge state of europium. We have shown that Eu3+ predominates over Eu2+ in samples obtained by coprecipitation of europium with calcium fluoride, and the ratio Eu3+\\/Eu2+ grows as the total amount of europium increases. Partial charge conversion of the europium occurs during calcination of the samples, due to

M. I. Danilkin; A. P. Belousov; S. O. Klimonskii; V. D. Kuznetsov; A. L. Lust; V. N. Nikiforov; L. N. Paama; I. Kh. Pammo; V. O. Seeman

2007-01-01

267

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

268

Bulk and surface valence in YbPd/sub x/ compounds  

SciTech Connect

The bulk and surface valence v-bar of Yb is investigated for YbPd/sub x/ intermetallic compounds (with x = 1,1.33,3) by photoemission using synchrotron radiation. YbPd is found to be of intermediate valence (v-barapprox. =2.75), while Yb/sub 3/Pd/sub 4/ and YbPd/sub 3/ are identified as bulk trivalent systems. The outermost atomic surface layer of both YbPd and Yb/sub 3/Pd/sub 4/ is found to be divalent, while only a fraction of Yb surface atoms turns divalent in YbPd/sub 3/. The results are compared with bremsstrahlung isochromat spectroscopy measurements and predictions based on Miedema's scheme.

Domke, M.; Laubschat, C.; Sampathkumaran, E.V.; Prietsch, M.; Mandel, T.; Kaindl, G.; Middelmann, H.U.

1985-12-15

269

High repetition rate, tunable femtosecond Yb-fiber laser  

Microsoft Academic Search

Using only a short piece of gain fiber, a 570 MHz Yb-fiber oscillator was set up and mode-locked via NPE, assisted by spectral filtering. Tuning the filter enables changing both center wavelength or optical bandwidth.

T. Wilken; P. Vilar-Welter; T. W. Hansch; Th. Udem; T. Steinmetz; R. Holzwarth

2010-01-01

270

Photodarkening rate in Yb-doped silica fibers  

NASA Astrophysics Data System (ADS)

Yb-doped fibers are widely used in laser applications requiring high average output powers and high-peak-power pulse amplification. Photodarkening (PD) is recognized as one limiting factor in these fibers when pumped with high-intensity radiation. We describe an approach for performing quantitative PD studies of fibers, and we present measurements of the rate of PD in Yb-doped single-mode fibers with varying inversion levels. The method is applicable to large-mode-area fibers. We observed a seventh-order dependence of the PD rate on the excited-state Yb concentration for two different fibers; this result implies that PD of a Yb-doped fiber source fabricated using a particular fiber will be strongly dependent on the configuration of the device.

Koponen, Joona; Söderlund, Mikko; Hoffman, Hanna J.; Kliner, Dahv A. V.; Koplow, Jeffrey P.; Hotoleanu, Mircea

2008-03-01

271

Growth and spectral properties of Yb:FAP single crystal  

NASA Astrophysics Data System (ADS)

In this paper, single crystal of ytterbium (Yb) doped Ca5(PO4)3F (FAP) has been grown along the c-axis by using the Czochralski method. The segregation coefficients of Yb3+ in the Yb:FAP crystal has been determined by ICP-AES method. The absorption spectrum, fluorescence spectrum and fluorescence lifetime of the Yb:FAP crystal has been also measured at room temperature. In the absorption spectra, there are two absorption bands at 904 and 982 nm, respectively, which are suitable for InGaAs diode laser pumping. The absorption cross-section (?abs) is 5.117 × 10-20 cm2 with an FWHM of 4 nm at 982 nm. The emission cross-section (?em) is 3.678 × 10-20 cm2 at 1042 nm. Favorable values of the absorption cross-section at about 982 nm are promising candidates for laser diode (LD) pumping.

Song, Pingxin; Zhao, Zhiwei; Xu, Xiaodong; Deng, Peizhen; Xu, Jun

2007-01-01

272

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

273

Magnetic field tuning of antiferromagnetic Yb3Pt4  

Microsoft Academic Search

We present measurements of the specific heat, magnetization, magnetocaloric effect, and magnetic neutron diffraction carried out on single crystals of antiferromagnetic Yb3Pt4, where highly localized Yb moments order at TN=2.4 K in zero field. The antiferromagnetic order was suppressed to TN-->0 by applying a field of 1.85 T in the ab plane. Magnetocaloric effect measurements show that the antiferromagnetic phase

L. S. Wu; Y. Janssen; C. Marques; M. C. Bennett; M. S. Kim; Songxue Chi; J. W. Lynn; G. Lorusso; G. Biasiol; M. C. Aronson

2011-01-01

274

LD-pumped slab Yb:YAG laser  

NASA Astrophysics Data System (ADS)

In recent years, the high power Yb:YAG lasers have been actively investigated due to the advantage of the high quantum efficiency of 91% which reduces the thermal loading in the Yb:YAG crystal. So far, the Yb:YAG laser with the output power higher than several hundreds watts has been developed using the crystal configurations of rod and thin disk. We have developed the Yb:YAG laser by employing the rectangular slab crystal in order to examine the possibility of realizing the high power slab Yb:YAG laser. The dimension of the Yb:YAG crystal used is 1 mm X 5 mm X 10 mm and its configuration is a rectangular parallelepiped, and the density of Yb is 1.1 atom%. The LD (Laser Diode) pump light focused with plano-convex lens is introduced through the 1 mm X 10 mm plane of this slab which is AR-coated at 940 nm while the opposite 1 mm X 10 mm plane is HR-coated at the same wavelength. The Yb:YAG laser cavity axis is in the direction perpendicular to the 1 mm X 5 mm planes which are AR-coated at 1030 nm. The two 5 mm X 10 mm planes are cooled by being contacted with the copper heat sinks which are cooled by the water at the temperature of 18 degrees Celsius. The CW output of 35 W was obtained when the power of LD pump light was 496 W. The optical efficiency was 7.1% with the optical slop efficiency of 12.2%.

Sato, Masao; Iehisa, Nobuaki; Karube, Norio

2000-04-01

275

[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

276

Growth and spectroscopic characteristics of Yb:LPS single crystal  

NASA Astrophysics Data System (ADS)

For the first time, a high optical quality Yb3+-doped lutetium pyrosilicate laser crystal Lu2Si2O7 (LPS) was grown by the Czochralski (Cz) method. The segregation coefficient of ytterbium ion in Yb:LPS crystal detected by the inductively coupled plasma atomic emission spectrometer (ICP-AES) method is equal to 0.847. X-ray powder diffraction result confirms the C2/m phase monoclinic space group of the grown crystal and the peaks corresponding to different phases were indexed. The absorption and fluorescence spectra, as well as fluorescence decay lifetime of Yb3+ ion in LPS have been investigated. The absorption and fluorescence cross-sections of the transitions 2F7/2?2F5/2 of Yb3+ ion in LPS crystal have been determined. The advantages of the Yb:LPS crystal including high crystal quality, quasi-four-level laser operating scheme, high absorption cross-sections (1.33×10-20 cm2) and particularly broad emission bandwidth (˜62 nm) indicated that the Yb:LPS crystal seemed to be a promising candidate used as compact, efficient thin chip lasers when LD is pumped at 940 and 980 nm due to its low-symmetry monoclinic structure and single crystallographic site.

Zheng, Lihe; Zhao, Guangjun; Yan, Chengfeng; Yao, Gang; Xu, Xiaodong; Su, Liangbi; Xu, Jun

2007-06-01

277

Yb :CALGO as material for high power ultrafast laser and focus on thermal conductivity variation  

NASA Astrophysics Data System (ADS)

Thermal conductivity values of laser material Yb3+:CaGdAlO4 (CALGO) with various doping rate in Yb3+ were measured experimentally and compared to predictive values obtained by modelling. The observed variation of the thermal conductivity with the Yb3+ content could be explained by changing the ratio of site substitution Gd3+/Ca2+ by Yb3+. The influence of velocity sound and interionic distance values on thermal conductivity was also studied. Finally, laser results obtained with a 2%Yb:CALGO thin-disk were presented, strengthening the potential of Yb:CALGO for high power laser and ultra-short pulses generation.

Jaffrès, A.; Ricaud, S.; Suganuma, A.; Viana, B.; Loiseau, P.; Georges, P.; Druon, F.

2013-03-01

278

Crystal-field splitting of energy levels of rare-earth ions Dy3+(4f9) and Yb3+(4f13) in M(II) sites in the fluorapatite crystal Sr5(PO4)3F  

Microsoft Academic Search

We have calculated a set of crystal-field parameters, Bnm, for Dy3+ through Yb3+ ions in M (II) sites in the crystal Sr5(PO4)3F (SFAP). The Bnm parameters were derived from lattice-sum calculations and from analyses of the optical spectra reported for Ho3+, Er3+, and Tm3+ individually doped into SFAP. These parameters were used to predict starting values, which were then semiempirically

John B. Gruber; Bahram Zandi; Larry Merkle

1998-01-01

279

Analysis of energy transfer processes in Yb3+Tb3+ co-doped, low-silica calcium aluminosilicate glasses  

Microsoft Academic Search

Energy transfer processes in Yb3+-Tb3+ co-doped, low-silica calcium aluminosilicate glasses were analyzed. Luminescence and time-resolved measurements were used to study upconversion processes, such as Yb-Tb cooperative sensitization, Yb-Yb cooperative luminescence, and Yb-Tb cross relaxation. The quantum cross relaxation efficiency was evaluated as a function on the Yb3+ concentration, and the maximum estimated value was approximately 51%. In addition, the intensity

I. A. A. Terra; L. J. Borrero-Gonza´lez; L. A. O Nunes; J. H. Rohling; M. L. Baesso; O. L. Malta

2011-01-01

280

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

281

Identification of proteins specifically interacting with YB-1 mRNA 3' UTR and the effect of hnRNP Q on YB-1 mRNA translation.  

PubMed

In this study, proteins specifically interacting with the 3' untranslated region (UTR) of mRNA of the multifunctional Y-box-binding protein 1 (YB-1) were identified. One of these, hnRNP Q, was shown to specifically interact with the regulatory element (RE) in YB-1 mRNA 3' UTR and to inhibit translation of this mRNA. Its binding to the RE was accompanied by displacement from this element of the poly(A)-binding protein (PABP), a positive regulator of YB-1 mRNA translation, and by enhanced binding of the negative YB-1 mRNA translation regulator - YB-1 itself. PMID:23980891

Lyabin, D N; Nigmatullina, L F; Doronin, A N; Eliseeva, I A; Ovchinnikov, L P

2013-06-01

282

Preparation and analysis of Eu 3+- and Eu 2+-doped ZBLAN and ZBLALi fluorozirconate glasses  

Microsoft Academic Search

Fluorozirconate glasses in the ZBLAN and ZBLALi families with varying [Eu2+] and [Eu3+] concentrations were prepared and characterized. The reversible electroactivity of Eu2+\\/3+ was verified by cyclic voltammetry in the molten salt precursor phase, showing that Eu2+ would not reduce the other glass components. Eu2+-containing glasses were prepared by various strategies including inclusion of EuF2 as a starting material and

Bruce Phebus; Boris Getman; Shane Kiley; David Rauser; Mischa Plesha; Roger H. Terrill

2005-01-01

283

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

284

The new binary intermetallic YbGe{sub 2.83}  

SciTech Connect

The new compound YbGe{sub 2.83} was obtained from the reaction of Yb and Ge in liquid indium. The crystal structure of YbGe{sub 2.83} adopts the trigonal, P3m1 space group with a=b=8.3657(12) A and c=7.0469(14) A. The structure of YbGe{sub 2.83} is a variant of the CaAl{sub 2}Si{sub 2} structure type with ordered vacancies. Germanium atoms form double layers of puckered hexagons creating slabs that sandwich the Yb atoms. YbGe{sub 2.83} can be classified as a Zintl compound with the formula Yb{sup (2+x)+}(Ge{sub 2.83}){sup (2+x)-}. The deficiencies at the Ge sites cause a mixed/intermediate valent state of ytterbium (Yb{sup 2.35+}). Valence bond sum calculations suggest an average valence of Yb ions in YbGe{sub 2.83} of 2.51 consistent with an intermediate valence compound. - Graphical abstract: The new binary compound YbGe{sub 2.83} is a variant of the CaAl{sub 2}Si{sub 2} structure type with ordered vacancies. Zintl formalism and valence bond sum calculations suggest intermediate valence of Yb ions in YbGe{sub 2.83}.

Peter Sebastian, C. [Department of Chemistry, Northwestern University, 2145 N. Sheridan Road, Evanston, IL 60208-3113 (United States); Kanatzidis, Mercouri G., E-mail: m-kanatzidis@northwestern.ed [Department of Chemistry, Northwestern University, 2145 N. Sheridan Road, Evanston, IL 60208-3113 (United States)

2010-09-15

285

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

286

Crystal field excitations of YbMn2Si2  

NASA Astrophysics Data System (ADS)

The crystal field excitations of the rare earth intermetallic compound YbMn2Si2 have been measured by inelastic neutron scattering over the temperature range 2.5-50 K. The YbMn2Si2 spectra exhibit three low energy excitations (~3-7 meV) in the antiferromagnetic AFil region above the magnetic phase transition at TN2 = 30(5) K. The crystal field parameters have been determined for YbMn2Si2 in the antiferromagnetic AFil region. A further two inelastic excitations (~9 meV, 17 meV) are observed below TN2=30(5) K, the temperature at which the high temperature antiferromagnetic structure is reported to exhibit doubling of the magnetic cell. Energy level diagrams have been determined for Yb3+ ions in the different sites above (single site) and below the magnetic transition temperature (two sites). The excitation energies for both sites are shown to be temperature independent with the temperature dependences of the transition intensities for the two sites described well by a simple Boltzmann model. The spectra below TN2 cannot be described fully in terms of molecular field models based on either a single Yb3+ site or two Yb3+ sites. This indicates that the magnetic behaviour of YbMn2Si2 is more complicated than previously considered. The inability to account fully for excitations below the magnetic phase transition may be due to an, as yet, unresolved structural transition associated with the magnetic transition.

Mole, R. A.; Hofmann, M.; Adroja, D. T.; Moze, O.; Campbell, S. J.

2013-12-01

287

Spectral Properties of ZnO-LiYbO2 Hybrid Phosphor for Silicon Solar Cell  

NASA Astrophysics Data System (ADS)

We report on the luminescent properties of ZnO-LiYbO2 hybrid phosphor, in which the broadband spectral modification can be realized to benefit the enhancement of silicon solar cell photovoltaic conversion efficiency. Under the excitation of ZnO band-band absorption and exciton absorption in the near-UV region, the intense Yb3+ emission around 1000 nm can be observed. The occurrence of energy transfer from ZnO to Yb3+ was proved by the excitation and emission measurement. The emission spectra between the ZnO-LiYbO2 hybrid phosphor and the LiYbO2 crystal under the direct excitation of Yb3+ ions with 937 nm LD was compared, which indicates that the Yb3+ ions that were diffused into ZnO lattice with the help of Li+, rather than those constitute of LiYbO2 crystals, are responsible for the intense infrared emission.

Ye, Song; Tanabe, Setsuhisa; Qiu, Jianrong

2011-05-01

288

Yb-doped mixed sesquioxides for ultrashort pulse generation in the thin disk laser setup  

NASA Astrophysics Data System (ADS)

We report on spectroscopic investigations of the mixed sesquioxide laser materials Yb:LuScO3, Yb:YScO3, and Yb:(Lu,Y,Sc)2O3 as well as mode-locked thin disk laser experiments with Yb:LuScO3 and Yb:(Lu,Y,Sc)2O3. The disordered crystal structures of these materials result in significantly broader emission spectra than for the pure sesquioxides Yb:Sc2O3, Yb:Y2O3, and Yb:Lu2O3 providing a high potential for ultrashort pulse generation. In SESAM mode-locked thin disk laser experiments, pulse durations of around 100 fs could be obtained exploiting >70 % of the gain bandwidth which is to the best of our knowledge the optimum obtained so far for the mode-locked lasers in this setup.

Beil, Kolja; Saraceno, Clara J.; Schriber, Cinia; Emaury, Florian; Heckl, Oliver H.; Baer, Cyrill R. E.; Golling, Matthias; Südmeyer, Thomas; Keller, Ursula; Kränkel, Christian; Huber, Günter

2013-04-01

289

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

290

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

291

Dielectric grating waveguides operating with TM polarization  

Microsoft Academic Search

The frequency selective characteristics of waveguides with a dielectric grating and operating with TM polarization are analyzed, having in mind their use as dichroic surfaces. The formulation is similar to that used to analyze waveguide structures operating with TE polarization. The results an valuable for the design of these structures

L. P. de Oliveira; A. J. Giarola; J. C. W. A. Costa

1996-01-01

292

FANTESK**TM PROCESSING AND UTILIZATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Fantesk**TM is a stable dispersion of a jet-cooked starch slurry-oil mixture. The jet cooked material can be air- or drum-dried. Jet cooking and shear of the mixture liquefies the starch and lowers its MW. Various oils and fats and different starches can be used to produce Fantesk. Fantesk is a ...

293

PM3(tm) parameterization using genetic algorithms  

SciTech Connect

PM3(tm) has great potential in studying transition metals because of its speed and applicability to large complexes. However, its parameterization is not yet available for all 30 d-block metals. In this research, genetic algorithms (GAs) were evaluated for the development of PM3(tm) parameters for technetium (Tc). Initial Tc parameters were obtained by interpolation of parameters for the metals flanking it in the periodic table--molybdenum and ruthenium. Prototypical Tc compounds were chosen from the Cambridge Structural Database. The sensitivities of the 21 PM3(tm) parameters were tested using different methods and their impact on molecular geometry assessed. The fitness criterion was based on the root mean square (rms) of the distance matrix between calculated and crystal structures. The GA-optimized parameters improved the calculated structural accuracy by more than 50% versus interpolated parameters. In addition, structural prediction (bond lengths within 0.04 {angstrom}, bond angles within 2{degree}, dihedral angles with 4{degree}) with the GA-developed parameters for Tc is competitive with those already available in PM3(tm) and with that expected from high-level ab initio calculations, but in a fraction of the time.

Cundari, T.R.; Deng, J.; Fu, W.

2000-03-05

294

New EU regulations in endoscopy.  

PubMed

As a result of European unification, new regulations valid within the territory of the European Union (EU) have been negotiated and published. As in other medical fields, the Medical Device Directive (MDD) is the most important new regulation and also effects endoscopy. In a transition period until June 1998, the MDD will be transposed into national law by the member states of the EU. Compliance with the MDD and other European regulations is indicated by the CE mark affixed to the product. PMID:8565892

Wächter, M; Diekjobst, T

1995-09-01

295

Enhanced 1.47 ?m emission and lowered upconversion of Tm3+-doped gallate-germanium-bismuth-lead glass by codoping rare earths  

NASA Astrophysics Data System (ADS)

An intense broadband 1.47 ?m emission with a full width at half maximum of 125 nm and a peak emission cross section of 4.056×10-21 cm2 of the Tm3+-doped gallate-germanium-bismuth-lead (GGBP) glass has been obtained upon 808 nm diode-laser excitation. Effects of rare-earth (RE3+=Ho3+, Tb3+, Eu3+, Dy3+) codoping on the spectroscopic properties of the Tm3+-doped GGBP glass have been investigated. It is found that the incorporation of RE3+ into the Tm3+-doped GGBP glass can effectively improve the 1.47 ?m emission and can deduce the upconversion luminescence, which makes the GGBP glass more attractive to use in S-band optical fiber amplifiers.

Shi, D. M.; Zhang, Q. Y.

2008-12-01

296

The tmRNA Website: invasion by an intron  

Microsoft Academic Search

tmRNA (also known as 10Sa RNA or SsrA) plays a central role in an unusual mode of translation, whereby a stalled ribosome switches from a prob- lematic mRNA to a short reading frame within tmRNA during translation of a single polypeptide chain. Research on the mechanism, structure and biology of tmRNA is served by the tmRNA Website, a collection of

Kelly P. Williams

2002-01-01

297

Measurement of high-photodarkening resistance in phosphate fiber doped with 12% Yb2O3  

Microsoft Academic Search

We report the measurement of photodarkening in single-mode phosphate fibers with a Yb3+ concentrations of 7.1 × 1026 m-3 and 1.42 × 1027 m-3 (6 wt.% and 12 wt.% Yb2O3).We compare the photodarkening resistance of these phosphate fibers with that of three single-mode Yb3+-doped silica fibers. Our data shows that under strong pumping conditions, phosphate fibers allow Yb3+ concentrations that

Y. W. Lee; S. Sinha; M. J. F. Digonnet; R. L. Byer; S. Jiang

2008-01-01

298

GeneyTM: designing a collaborative activity for the palmTM handheld computer  

Microsoft Academic Search

This paper describes a project to explore issues surrouding the development of a collaborative handheld educational application for children. A user-centered, iterative design process was used to develop GeneyTM, a collaborative problem solving application to help children explore genetic concepts using PalmTM handheld computers. The design methodology utilized mock-ups of representative tasks and scenarios, pre-design meetings with targets users, prototype

Arman Danesh; Kori Inkpen; Felix Lau; Keith Shu; Kellogg S. Booth

2001-01-01

299

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

300

Morocco-EU Trade Relations  

Microsoft Academic Search

The European Union is Morocco's main trading partner. In 2008 Moroc- co-EU bilateral merchandise trade represented some 60 percent of total Moroccan merchandise trade with the world (table 10.1). Since the Asso- ciation Agreement entered into force in 2000, bilateral merchandise trade between the two partners has tripled. The increase has been especially signifi cant on the import side, but

CLAIRE BRUNEL

301

Inside the China–EU FDI Bond  

Microsoft Academic Search

For some 20 years, the rate of investment by EU enterprises into China has been rising, reaching an annual average of some US$5bn over the 10 years to 2009. Conversely, the EU has not been a focus for Chinese investments, nor has Chinese investment been important to the EU despite the wide attention given to recent landmark cross?border acquisitions. Therefore,

Jeremy Clegg; Hinrich Voss

2011-01-01

302

Reliability and Validity of the Zephyr[TM] BioHarness[TM] to Measure Respiratory Responses to Exercise  

ERIC Educational Resources Information Center

|The Zephyr[TM] BioHarness[TM] (Zephyr Technology, Auckland, New Zealand) is a wireless physiological monitoring system that has the ability to measure respiratory rate unobtrusively. However, the ability of the BioHarness[TM] to accurately and reproducibly determine respiratory rate across a range of intensities is currently unknown. The aim of…

Hailstone, Jono; Kilding, Andrew E.

2011-01-01

303

Orthorhombic superstructures within the rare earth strontium-doped cobaltate perovskites: Ln 1? x Sr x CoO 3? ? ( Ln=Y 3+, Dy 3+–Yb 3+; 0.750? x?0.875)  

Microsoft Academic Search

A combination of electron, synchrotron X-ray and neutron powder diffraction reveals a new orthorhombic structure type within the Sr-doped rare earth perovskite cobaltates Ln1?xSrxCoO3?? (Ln=Y3+, Dy3+, Ho3+, Er3+, Tm3+and Yb3+). Electron diffraction shows a C-centred cell based on a 2?2ap×4ap×4?2ap superstructure of the basic perovskite unit. Not all of these very weak satellite reflections are evident in the synchrotron X-ray

Michael James; Maxim Avdeev; Paris Barnes; Liliana Morales; Kia Wallwork; Ray Withers

2007-01-01

304

Optimization of Yb+ fluorescence and hyperfine-qubit detection  

NASA Astrophysics Data System (ADS)

Fluorescence of single, trapped Yb171+ ions has been experimentally studied as a function of laser polarization, power, and detuning and as a function of magnetic field strength. The suppression of efficient fluorescence by coherent population trapping and the counteracting effect of the magnetic field are found to agree with theoretical predictions. For comparison, a fluorescence study has also been made of the isotope Yb174+ for which coherent population trapping is absent on the main fluorescence and laser cooling transition. Finally, state-sensitive fluorescence detection of the Yb171+ hyperfine qubit is studied, including the role of coherent population trapping in the optimization of detection parameters. A qubit detection fidelity of greater than 97% is achieved.

Ejtemaee, S.; Thomas, R.; Haljan, P. C.

2010-12-01

305

Origins of Phase Transitions in Valence Fluctuating YbPd  

NASA Astrophysics Data System (ADS)

The cubic YbPd compound undergoes two first-order phase transitions at T1=125 K and T2=105 K. We report the experimental results of the X-ray diffraction (XRD) and electron diffraction of single crystals of YbPd at low temperatures. Below T1, the (h00) Bragg peaks (h: an integer) are split into two subpeaks. Below T2, the superlattice reflections of (n/2,0,0) (n: an odd number) in the XRD patterns and the superlattice spots of (1/2,0,0), (0,1/2,0), and (1/2,1/2,0) in the electron diffraction profile appear, which suggests the valence order of YbPd. We discuss two possible structures, assuming a tetragonal symmetry below T1. The origins of the transitions at T1 and T2 are probably the band Jahn--Teller effect and the valence order, respectively.

Mitsuda, Akihiro; Sugishima, Masaki; Hasegawa, Takumi; Tsutsui, Satoshi; Isobe, Masahiko; Ueda, Yutaka; Udagawa, Masayuki; Wada, Hirofumi

2013-08-01

306

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

307

Phonon Dispersion in the Fcc Metals Ca, Sr and Yb  

NASA Astrophysics Data System (ADS)

Within the harmonic approximation and adiabatic approximation, the expressions of atomic force constants have been derived. Phonon dispersion curves along four major symmetry directions and four off-symmetry directions have been simulated for alkaline-earth metals Ca, Sr and the rare-earth metal Yb by combining the modified analytic embedded atom method with the theory of lattice dynamics. The simulated phonon dispersion curves for the fcc metals Ca, Sr and Yb along four major symmetry directions have been compared to the corresponding experimental data. The results show that the simulated results are general consistent with available experimental results, with a maximum deviation of approximately 14 %. The simulated phonon frequencies of the fcc metals Ca, Sr and Yb lay a significant foundation for guiding and judging relative experiment results, especially for the phonon dispersion relation along off-symmetry directions.

Zhang, Xiao-Jun; Chen, Chang-Le

2012-10-01

308

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

309

Laser performance of Yb3+ doped oxyorthosilicates LYSO and GYSO.  

PubMed

Ytterbium offers a number of advantages as the active ion in solid-state laser crystals, but is hindered by the disadvantages of a three level lasing scheme. Yb(3+)-doped oxyorthosilicates have emerged in recent years as potentially quasi-four level laser materials. Two such crystals, Yb:GdYSiO(5) and Yb:LuYSiO(5), are investigated to determine the extent of four-level behavior. It is shown that these crystals demonstrate a significant reduction in the pump intensity required to reach threshold, but still exhibit three-level effects in terms of self-absorption, population inversion, and thermal sensitivity. The important material properties such as the coefficient of thermal expansion and the thermo-optic coefficient are measured. PMID:19434180

Brickeen, Brian K; Geathers, Eliot

2009-05-11

310

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

311

Magnetisation dynamics of YbIr2Si2  

NASA Astrophysics Data System (ADS)

The two crystallographic modifications of YbIr2Si2 are supposed to be located on either side of a quantum phase transition. We here report on inelastic neutron scattering experiments investigating the magnetisation dynamics in the paramagnetic state. The observed magnetic scattering in the energy range of about 15 40 meV has been attributed to crystalline electric field (CEF) transitions. We relate our findings to the magnetic properties of the non-Fermi-liquid (NFL) YbRh2Si2.

Hiess, A.; Stockert, O.; Koza, M. M.; Hossain, Z.; Geibel, C.

2006-05-01

312

High-K bands in the 166Yb region  

NASA Astrophysics Data System (ADS)

High-K bands have been observed in the 166,167,168Yb isotopes following the 124Sn(48Ca,xn?) reaction. The ?h11/2 band in 167Yb has been extended to higher spins. The high-K bands in the even-even isotopes were observed for the first time and show very high B(M1)/B(E2) ratios. Configuration assignments for the new bands are proposed. The results are interpreted within the Tilted Cranking model.

Oliveira, J. R.; Frauendorf, S.; Deleplanque, M. A.; Cederwall, B.; Diamond, R. M.; Macchiavelli, A. O.; Stephens, F. S.; Burde, J.; Draper, J. E.; Duyar, C.; Rubel, E.; Becker, J. A.; Henry, E. A.; Brinkman, M. J.; Kuhnert, A.; Stoyer, M. A.; Wang, T. F.

1994-09-01

313

Heavy quasiparticles formed in the ferromagnetic Yb layers in the Kondo helical magnet YbNi3Al9 as revealed by specific-heat measurements  

NASA Astrophysics Data System (ADS)

We report specific-heat and magnetocaloric-effect studies on single-crystalline Kondo helical magnet YbNi3Al9. Molecular field analysis of a Schottky peak due to the Zeeman splitting of the Yb-ion doublet crystalline-field ground state demonstrates that the interlayer antiferromagnetic exchange interactions are 2 orders of magnitude smaller than that of the intralayer ferromagnetic coupling among Yb ions, reflecting realization of magnetically well separated Yb layers. The Sommerfeld coefficient ?, which is 110 mJ/K2mol in zero field, decreases smoothly with increasing field without any noticeable anomalies at the helical magnetic phase boundary. This fact confirms that heavy quasiparticles are formed on a part of the Fermi surface away from “hot sheets” that have nesting instabilities responsible for the helical magnetic structure. These results indicate that YbNi3Al9 is a novel system where heavy quasiparticles are confined within the two-dimensional Yb layers.

Miyazaki, Ryoichi; Aoki, Yuji; Higashinaka, Ryuji; Sato, Hideyuki; Yamashita, Testuro; Ohara, Shigeo

2012-10-01

314

Crystal growth of CsCl-type Yb 0.24Sn 0.76Ru  

Microsoft Academic Search

The Yb–Ru–Sn ternary system was investigated and a new material, Yb0.24Sn0.76Ru, with a simple cubic crystal structure, was discovered. Yb0.24Sn0.76Ru has a smaller lattice parameter a=3.217(4)Å, than its isostructural YbRu analogue (a=3.360Å). Both X-ray diffraction and electron microscopy techniques were used to refine the crystal structure of Yb0.24Sn0.76Ru. It was found that a new compound forms in the CsCl structure,

T. Klimczuk; C. H. Wang; Q. Xu; J. Lawrence; T. Durakiewicz; F. Ronning; A. Llobet; E. D. Bauer; J. C. Griveau; W. Sadowski; H. W. Zandbergen; J. D. Thompson; R. J. Cava

2011-01-01

315

Mass fabrication of homogeneously Yb-doped silica nanoparticles and their spectroscopic properties.  

PubMed

A large number of homogeneously Yb-doped silica nanoparticles were continually fabricated in a vapor synthesis route, in which the Yb doping level can be well controlled by varying either the heating temperature or the carrier gas flow rate of the Yb precursor. The sizes, shapes, and morphologies of the nanoparticles were examined, and no crystallites and no Yb2O3 clusters were observed in the nanoparticles. These nanoparticles exhibit a clear Yb3+-derived absorption at around 973-975 nm and a dependence of the emission intensity and decay time on the doping level, much different from that of sintered pellets. PMID:19417259

Xiong, Liangming; Sekiya, Edson H; Saito, Kazuya

2008-12-08

316

Mass fabrication of homogeneously Yb-doped silica nanoparticles and their spectroscopic properties  

NASA Astrophysics Data System (ADS)

A large number of homogeneously Yb-doped silica nanoparticles were continually fabricated in a vapor synthesis route, in which the Yb doping level can be well controlled by varying either the heating temperature or the carrier gas flow rate of the Yb precursor. The sizes, shapes, and morphologies of the nanoparticles were examined, and no crystallites and no Yb2O3 clusters were observed in the nanoparticles. These nanoparticles exhibit a clear Yb3+-derived absorption at around 973-975 nm and a dependence of the emission intensity and decay time on the doping level, much different from that of sintered pellets.

Xiong, Liangming; Sekiya, Edson H.; Saito, Kazuya

2009-01-01

317

Traffic at the tmRNA Gene  

Microsoft Academic Search

A partial screen for genetic elements integrated into completely sequenced bacterial genomes shows more significant bias in specificity for the tmRNA gene (ssrA) than for any type of tRNA gene. Horizontal gene transfer, a major avenue of bacterial evolution, was assessed by focusing on elements using this single attachment locus. Diverse elements use ssrA; among enterobacteria alone, at least four

Kelly P. Williams

2003-01-01

318

Measurement of thermal neutron cross-section and resonance integral for the 174Yb(n,gamma)175Yb reaction by the cadmium ratio method  

Microsoft Academic Search

The thermal-neutron cross-section and the resonance integral for the 174Yb(n,gamma)175Yb reaction were measured by the activation method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am Be neutron sources. The gamma-ray spectra from the

Mustafa Karadag; Haluk Yücel

2008-01-01

319

Measurement of thermal neutron cross-section and resonance integral for the 174Yb(n,?) 175Yb reaction by the cadmium ratio method  

Microsoft Academic Search

The thermal-neutron cross-section and the resonance integral for the 174Yb(n,?)175Yb reaction were measured by the activation method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am–Be neutron sources. The gamma-ray spectra from the activated samples

Mustafa Karadag; Haluk Yücel

2008-01-01

320

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

2013-04-26

321

Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3/Si multilayer deposited on Si substrates  

NASA Astrophysics Data System (ADS)

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.

Li, Leliang; Zheng, Jun; Zuo, Yuhua; Cheng, Buwen; Wang, Qiming

2013-04-01

322

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

323

PLD-grown Yb-doped Sesquioxide Films on Sapphire and Quartz Substrates  

NASA Astrophysics Data System (ADS)

This paper focuses on the fabrication and characterization of crystalline Yb-doped sesquioxide films (Yb2O3, Yb:Lu2O3, Yb:Sc2O3) grown by pulsed laser deposition on single crystal sapphire (?-Al2O3) and quartz (?-SiO2) substrates as well as on lutetia (Lu2O3) and scandia (Sc2O3) substrates. Such ytterbium doped active films can be promising for use in a thin-disk laser setup. X-Ray diffraction measurements show that the films grow highly textured along <111> direction. The ?-scan (rocking curve) shows deviation of the crystallite orientation ~4° in case of Lu2O3 and Yb2O3 films and <1° for Sc2O3 films. Yb2O3 films reveal no luminescence at room temperature and the well known Yb3+ emission in the 975-980 nm region (zero-phonon line) can only be observed at temperatures below 20 K. A similar effect is observed in a bulk Yb2O3 crystal. Ytterbium emission and excitation spectra measured at room temperature for Yb(5%):Lu2O3 and Yb(4%):Sc2O3 films resemble those of the bulk crystal very closely. Luminescence decay lifetimes are also comparable to those measured in a bulk crystal. This indicates a high quantum efficiency of the Yb3+-emission and allows application of such films as active media for thin disk lasers.

Kuzminykh, Yury; Scheife, Hanno; Bär, Sebastian; Petermann, Klaus; Huber, Günter

2007-04-01

324

Dosimetric characterization of a new preparation of BaSO4 activated by Eu ions  

NASA Astrophysics Data System (ADS)

The results of a thermoluminescent investigation carried out on a new preparation of BaSO4 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 BaSO4:Eu. The highest sensitivity was found for BaSO4: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 BaSO4: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

325

Passively Q-switched Yb(3+) laser with Yb(3+)-doped CaF(2) crystal as saturable absorber.  

PubMed

Passive Q-switching of a diode-pumped Yb:LYSO laser at 1060 nm with a Yb(3+) ions-doped CaF(2) crystal without the excited-state absorption (ESA) was demonstrated. An average output power of 174 mW with pulse duration of 5.6 mus and repetition rate of 27 kHz have been obtained under the unoptimized conditions. And the Q-switching conversion efficiency was as high as 51.7%. PMID:19532474

Su, Liangbi; Zhang, Dan; Li, Hongjun; Du, Juan; Xu, Yi; Liang, Xiaoyan; Zhao, Guangjun; Xu, Jun

2007-03-01

326

Comparative study of optical and scintillation properties of Tm3+:YAG, and Tm3+:LuAG single crystals  

NASA Astrophysics Data System (ADS)

The optical and scintillation properties of Tm3+-doped yttrium aluminum garnet Y3Al5O12 (YAG) and Tm3+-doped lutetium aluminum garnet Lu3Al5O12 (LuAG) are compared. The Tm3+-doped single crystals were grown by the micro-pulling down (?-PD) technique. Both crystals demonstrated some emission peaks originated from 4f–4f forbidden transition of Tm3+ under 241Am alpha-ray excitation. The scintillation decay time of Tm3+-doped YAG was similar to that of LuAG. When irradiated by the gamma-rays from a 137Cs source, the relative scintillation light yields of Tm:YAG was 90% greater than that of Tm:LuAG.

Fujimoto, Yutaka; Sugiyama, Makoto; Yanagida, Takayuki; Wakahara, Shingo; Suzuki, Shotaro; Kurosawa, Shunsuke; Chani, Valery; Yoshikawa, Akira

2013-09-01

327

NMR, high frequency EPR and magnetization studies of YF3:Tm3+ and TmF3  

NASA Astrophysics Data System (ADS)

Magnetic properties of single crystal and powder samples of thulium fluoride, TmF3 (orthorhombic Pnma space group), and single crystals of YF3 doped with the Tm3+ ions are studied by NMR, high-frequency EPR and dc-magnetometry. It is shown that TmF3 is a Van Vleck paramagnet. Zero field splitting between two lowest ground state energy levels (ground 3H6 multiplet) of Tm3+ ion in TmF3 crystal lattice is found to be ~6.5 cm-1. The 19F nuclear spin-lattice relaxation in TmF3 at liquid helium temperatures is driven by the fluctuating magnetic fields created by Tm3+ ions occupying the lowest excited singlet.

Savinkov, A. V.; Shakurov, G. S.; Korableva, S. L.; Dooglav, A. V.; Tagirov, M. S.; Suzuki, H.; Matsumoto, K.; Abe, S.

2011-10-01

328

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

329

Charge-transfer luminescence and spectroscopic properties of Yb3+ in aluminium and gallium garnets  

NASA Astrophysics Data System (ADS)

Luminescence of Yb3+ from the charge-transfer state with broad emission bands and short radiative lifetimes (few to tens of nanoseconds depending on the host lattice and the temperature) is attractive for the development of fast scintillators capable of discriminating very short events. The most important currently considered application is that in solar neutrino (?e) real-time spectroscopy, since the ?e capture by 176Yb is followed by a specific emission signature which can accordingly excite the Yb3+ fluorescence. Studies on scintillation and luminescence in aluminium garnets containing Yb3+ have shown that these materials meet some of the required properties for such scintillators. In defining our priorities, the best compromise between host crystal, Yb3+ concentration, production method, post-growth treatment and performance is to be considered based on the studies of charge-transfer luminescence and quenching mechanisms. The experiments have been extended to a large number of compounds: YAG:Yb-YbAG, YGG:Yb-YbGG, YAP:Yb-YbAP, LaYbO3 in the form of single crystals and/or powders. In garnets, the temperature-dependent fluorescence intensity and decay time under X-ray and VUV excitations decrease at low temperatures (T<100K) and demonstrate the important role played by the traps. The thermoluminescence peaks show a strong dependence on the crystal history, composition and impurities introduced intentionally. The fluorescence intensity and decay time are also dependent on Yb3+ concentration and the presence of Yb2+. The results trace the major directions to optimised scintillators in terms of their efficiency and lifetime.

Guerassimova, N.; Dujardin, C.; Garnier, N.; Pédrini, C.; Petrosyan, A. G.; Kamenskikh, I. A.; Mikhailin, V. V.; Shpinkov, I. N.; Spassky, D. A.; Ovanesyan, K. L.; Shirinyan, G. O.; Chipaux, R.; Cribier, M.; Mallet, J.; Meyer, J.-P.

2002-06-01

330

A Revised Periodic Table: With the Lanthanides Repositioned  

Microsoft Academic Search

The lanthanide elements from lanthanum to lutetium inclusive are incorporated into the body of the periodic table. They are\\u000a subdivided into three sub-groups according to their important oxidation states: La to Sm, Eu to Tm, Yb and Lu, so that Eu\\u000a and Yb fall directly below Ba; La, Gd, Lu form a column directly below Y; Ce and Tb fall

Michael Laing

2005-01-01

331

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

332

Highly efficient cryogenically-cooled Yb:YAG laser  

NASA Astrophysics Data System (ADS)

A MOPA laser system for high pulse energy and high average power has been developed by using a cryogenic Yb:YAG. In the regenerative amplifier with our original TRAM architecture, the high pulse energies of 6.5 and 1.5 mJ were obtained at the repetition rate of 200 Hz and 1 kHz, respectively. An optical efficiency was as high as ?o-o = 9.3% with an excellent beam quality of M 2 < 1.1, which ensured that a cryogenic Yb:YAG TRAM had a high thermal strength. The following four pass power amplifier with a cryogenic Yb:YAG rod showed 140 mJ at 100 Hz. Both a high optical efficiency of ?o-o = 30% and a high slope efficiency of ?s = 44% showed that an efficient laser operation could be realized for a power amplification with both a high pulse energy and a high average power by using a cryogenic Yb:YAG.

Kawanaka, J.; Takeuchi, Y.; Yoshida, A.; Pearce, S. J.; Yasuhara, R.; Kawashima, T.; Kan, H.

2010-05-01

333

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

334

Multimodal microscopy with sub-30 fs Yb fiber laser oscillator.  

PubMed

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. PMID:22808444

Nie, Bai; Saytashev, Ilyas; Chong, Andy; Liu, Hui; Arkhipov, Sergey N; Wise, Frank W; Dantus, Marcos

2012-06-27

335

Post-adsorption process of Yb phosphate nano-particle formation by Saccharomyces cerevisiae  

NASA Astrophysics Data System (ADS)

In this study, we have investigated the post-adsorption process of ytterbium (Yb) phosphate nano-particle formation by Saccharomyces cerevisiae (yeast). The yeast grown in P-rich medium were exposed to 1.44 × 10-4 mol/L Yb(III) solution for 2-120 h, and 2 months at 25 ± 1 °C at an initial pH of 3, 4, or 5, respectively. Ytterbium concentrations in solutions decreased as a function of exposure time. Field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (FESEM), transmission electron microscopy (TEM), and synchrotron-based extended X-ray absorption fine structure (EXAFS) analyses revealed that nano-sized blocky Yb phosphate with an amorphous phase formed on the yeast cells surfaces in the solutions with Yb. These nano-sized precipitates that formed on the cell surfaces remained stable even after 2 months of exposure at 25 ± 1 °C around neutral pHs. The EXAFS data revealed that the chemical state of the accumulated Yb on the cell surfaces changed from the adsorption on both phosphate and carboxyl sites at 30 min to Yb phosphate precipitates at 5 days, indicating the Yb-phosphate precipitation as a major post-adsorption process. In addition, the precipitation of Yb phosphate occurred on cell surfaces during 7 days of exposure in Yb-free solution after 2 h of exposure (short-term Yb adsorption) in Yb solution. These results suggest that the released P from the inside of yeast cells reacted with adsorbed Yb on cell surfaces, resulting in the formation of Yb precipitates, even though no P was added to the exposure solution. In an abiotic system, the EXAFS data showed that the speciation of sorbed Yb on the reference materials, carboxymethyl cellulose and Ln resin, did not change even when the Yb was exposed to P solution, without forming Yb phosphate precipitates. This result strongly suggests that the cell surface of the yeast plays an important role in the Yb-phosphate precipitation process, not only as a carrier of the functional groups but also as a substrate inducing the nucleation of phosphate nanoparticles. Stable nano-sized Yb phosphate precipitates formed on yeast cell surfaces in the present study, which implies that this post-adsorption nano-particle formation process caused by microbial cells should be one of the important processes governing the long-term migration of heavy rare earth elements and presumably trivalent actinides in geological repository.

Jiang, MingYu; Ohnuki, Toshihiko; Tanaka, Kazuya; Kozai, Naofumi; Kamiishi, Eigo; Utsunomiya, Satoshi

2012-09-01

336

Activation cross-section measurements for producing short-lived nuclei with 14 MeV neutrons—Ge, Pd, Yb  

NASA Astrophysics Data System (ADS)

Activation cross sections for 70Ge(n,p)70Ga, 74Ge(n,p)74Ga, 108Pd(n,p)108Rh, 110Pd(n,?)107Ru, and 174Yb(n,p)174Tm reactions producing short-lived nuclei with half-lives of several minutes were measured in the energy between 13.5 and 14.8 MeV using activation technique in this work. All cross-section values were relatively obtained on the basis of the standard cross section of 93Nb(n,2n)92Nb or 27Al(n,?)24Na, and the neutron energies were measured by the method of cross-sectional ratios for 90Zr(n,2n)89Zr to 93Nb(n,2n)92Nb reactions. Careful attention on corrections was paid to neutron irradiation and induced activities measurement. The measured results were discussed and compared with the previous works.

Lan, Chang-Lin; Fang, Kai-Hong; Xu, Xiao-San; Wang, Qi; Kong, Xiang-Zhong; Liu, Rong; Jiang, Li

2008-07-01

337

Visualizing tmRNA Entry into a Stalled Ribosome  

Microsoft Academic Search

Bacterial ribosomes stalled on defective messenger RNAs (mRNAs) are rescued by tmRNA, an ~300-nucleotide-long molecule that functions as both transfer RNA (tRNA) and mRNA. Translation then switches from the defective message to a short open reading frame on tmRNA that tags the defective nascent peptide chain for degradation. However, the mechanism by which tmRNA can enter and move through the

Mikel Valle; Reynald Gillet; Sukhjit Kaur; Anke Henne; V. Ramakrishnan; Joachim Frank

2003-01-01

338

Inside the China–EU FDI Bond  

Microsoft Academic Search

AbstractFor some 20 years, the rate of investment by EU enterprises into China has been rising, reaching an annual average of some US$5bn over the 10 years to 2009. Conversely, the EU has not been a focus for Chinese investments, nor has Chinese investment been important to the EU despite the wide attention given to recent landmark cross?border acquisitions. Therefore,

Jeremy Clegg; Hinrich Voss

339

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

340

LaVO4:Eu Phosphor films with enhanced Eu solubility  

NASA Astrophysics Data System (ADS)

Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO4: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 LaVO4 prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO4:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO4:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO4.

Higuchi, T.; Hotta, Y.; Hikita, Y.; Maruyama, S.; Hayamizu, Y.; Akiyama, H.; Wadati, H.; Hawthorn, D. G.; Regier, T. Z.; Blyth, R. I. R.; Sawatzky, G. A.; Hwang, H. Y.

2011-02-01

341

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

342

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

343

Correlation between electroluminescence and charge trapping in multi-color Eu implanted Si-based light-emitting diodes  

NASA Astrophysics Data System (ADS)

Electroluminescence (EL) spectra, charge trapping during operation of EL devices and clustering of rare earth oxides in SiO2 have been investigated in Eu implanted SiO2-Si structures which demonstrate luminescence associated with the light-emitting transitions in Eu2+ and Eu3+. Strong electron trapping in all studied regions of the injected charge (from 1×1014 to 1×1018 e/cm2) during operation of the light-emitting devices has been found that it considerably differed from the oxides implanted by other rare earth impurities (Ce, Tb, Gd, Er, Tm). It has been shown that the observed strong electron trapping and the low EL intensity in the Eu implanted structures were associated with enhanced clustering of the Eu oxides. The mechanism of electron trapping in the SiO2 containing a large cluster concentration is discussed, and flash lamp annealing is proposed to decrease the nanocluster size and to enhance the EL intensity.

Nazarov, A. N.; Tyagulskyy, I. P.; Tyagulskiy, S. I.; Rebohle, L.; Skorupa, W.; Biskupek, J.; Kaiser, U.

2009-05-01

344

Mechanism of tantalum adhesion on SiLK{sup TM}  

SciTech Connect

Tantalum adhesion on SiLK{sup TM} was investigated using first-principles method based on density functional theory. Phenylene groups were found to play a major role and the adjacent semi-benzene rings also contribute significantly to Ta adhesion on SiLK{sup TM}. In addition, the degradation effects of H{sub 2}/He reactive plasma clean on Ta adhesion on SiLK{sup TM} was investigated. Based on our findings, argon plasma treatment was suggested and implemented after reactive plasma cleaning process, which resulted in integration of SiLK{sup TM} with Cu up to seven metal layers.

Hu Yue; Yang Shuowang; Chen Xiantong; Lu Dong; Feng Yuanping; Wu Ping [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Institute of High Performance Computing, 1 Science Park Road, Singapore 117528 (Singapore); Institute of Microelectronics, 11 Science Park Road, Singapore 117685 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Institute of High Performance Computing, 1 Science Park Road, Singapore 117528 (Singapore)

2005-09-19

345

Yb{sub 3}AuGe{sub 2}In{sub 3} : an ordered variant of the YbAuIn structure exhibiting mixed-valent Yb behavior.  

SciTech Connect

Yb{sub 3}AuGe{sub 2}In{sub 3} was obtained as large single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data show that Yb{sub 3}AuGe{sub 2}In{sub 3} is an ordered variant of YbAuIn with lattice constants, a = b = 7.3153(8) {angstrom} and c = 4.4210(5) {angstrom}, and space group P{sub 6}2m. The parent compound YbAuIn was also studied for comparison. YbAuIn crystallizes in the ZrNiAl structure type, hexagonal, P{sub 6}2m space group with lattice parameters a = b = 7.7127(11) {angstrom} and c = 4.0294(8) {angstrom}. In Yb{sub 3}AuGe{sub 2}In{sub 3}, Ge substitutes for one of the two Au positions in the ternary compound Yb{sub 3}Au{sub 3}In{sub 3}. The structure can be described as alternating [Ge{sub 2}In{sub 3}] and [Yb{sub 3}Au] slabs that stack along the c-axis. The magnetic susceptibility data follow a modified Curie-Weiss law. The effective magnetic moment {mu}{sub eff} of 0.52 {micro}B/Yb atom was deduced from the Curie constant and Curie-Weiss constant of {Theta}{sub p} = -1.5 K indicating antiferromagnetic interactions in Yb{sub 3}AuGe{sub 2}In{sub 3}. X-ray absorption near edge spectroscopy (XANES) measurements indicate intermediate valency for Yb in both compounds. The metallic nature of both compounds was confirmed by the resistivity measurements. Specific heat data for Yb{sub 3}AuGe{sub 2}In{sub 3} and YbAuIn give an electronic {gamma} term of 31 and 84 mJ/mol {center_dot} K{sup 2}, respectively, suggesting that the ternary analog is a 'light' heavy fermion compound.

Chondroudi, M.; Peter, S. C.; Malliakas, C. D.; Balasubramanian, M.; Li, Q.; Kanatzidis, M. G. (Advanced Photon Source); ( MSD); (Michigan State Univ.); (Northwestern Univ.)

2011-01-01

346

Contribution of Eu 4f states to the magnetic anisotropy of EuO  

SciTech Connect

Anisotropic x-ray magnetic linear dichroism (AXMLD) provides a novel element-, site-, shell-, and symmetry-selective techniques to study the magnetic anisotropy induced by a crystalline electric field. The weak Eu2+ M4,5 AXMLD observed in EuO(001) indicates that the Eu 4f states are not rotationally invariant and hence contribute weakly to the magnetic anisotropy of EuO. The results are contrasted with those obtained for 3d transition metal oxides.

Arenholz, E.; Schmehl, A.; Schlom, D.G.; van der Laan, G.

2008-09-11

347

The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2}  

SciTech Connect

Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a=12.2261(20) Angstrom-Sign , b=10.7447(20) Angstrom-Sign , c=8.4754(17) Angstrom-Sign and {beta}=110.288(30) Degree-Sign (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge){sub n}. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a=b=5.9874(6) Angstrom-Sign and c=15.1178(19) Angstrom-Sign . The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{proportional_to}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures. - Graphical abstract: The compounds Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are obtained from reactions of Yb and Ge in excess liquid gallium. Highlights: Black-Right-Pointing-Pointer Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are two new polygallides. Black-Right-Pointing-Pointer The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was established using neutron diffraction data. Black-Right-Pointing-Pointer YbGa{sub 4}Ge{sub 2} is one of the rare polar intermetallic compounds. Black-Right-Pointing-Pointer The physical properties of Yb{sub 3}Ga{sub 7}Ge{sub 3} point to a Fermi-liquid regime at low temperature.

Peter, Sebastian C. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064 (India); Malliakas, Christos D. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Nakotte, Heinze; Kothapilli, Karunakar [Physics Department, New Mexico State University, Las Cruces, NM 88003 (United States); Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC, R-5 Shed, Trombay, Mumbai 400085 (India); Schultz, Arthur J. [X-Ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Kanatzidis, Mercouri G., E-mail: m-kanatzidis@northwestern.edu [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

2012-03-15

348

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

349

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

350

The unexpected EU leadership on landmines: the influence of the Ottawa Convention on the EU  

Microsoft Academic Search

The European Union (EU) has led international politics on antipersonnel landmines (APLs) for a decade now, and its foreign policy in this domain is perceived as a success story. Nevertheless, at the beginning of the negotiations that led to the Ottawa Convention, the EU looked unable to play any relevant part. This article addresses the emergence of the EU's foreign

Oriol Costa

2009-01-01

351

Spectrum and energy levels of the Yb4+ free ion (Yb V)  

NASA Astrophysics Data System (ADS)

The spectrum of ionized ytterbium produced by a sliding spark source was recorded on the 10 m high resolution vacuum ultraviolet normal-incidence spectrograph of the Meudon Observatory. About 1080 lines attributed to Yb V, hitherto unknown, have been identified. The analysis of this spectrum established all the energy levels of the ground configuration 4f12 and, respectively 174, 12 and 43 levels of the excited configurations 4f115d,4f116s and 4f116p. The theoretical calculations by means of the Cowan codes included a least-squares optimization of the relevant radial parameters by minimizing the differences between calculated and experimental level energies, which led to mean errors of 55 cm-1 for the 56 even parity levels and 51 cm-1 for the 186 odd parity ones. Interactions with the unknown core-excited configurations 5p54f13, 5p54f126p, 5p54f125d and 5p54f126s were taken into account.

Meftah, Ali; Wyart, Jean-François; Tchang-Brillet, Wan-Ü. Lydia; Blaess, Christophe; Champion, Norbert

2013-10-01

352

The dielectric properties enhancement due to Yb incorporation into HfO2  

NASA Astrophysics Data System (ADS)

The effects of Yb concentration and annealing temperature on the dielectric constant change of Yb-doped HfO2 thin film were investigated. The results show that the dielectric constant of Yb-doped HfO2 increased when doping with Yb after annealing. Compared with the undoped HfO2, the dielectric constant enhancement may result from the crystallographic change from monoclinic phase to the cubic phase. The Yb-doped HfO2 exhibited a lower leakage current than that of undoped HfO2 thin film. The electrical characteristics of Yb-doped HfO2 thin film illustrated that it is a promising gate dielectric layer for future high dielectric constant (high-k) gate dielectric applications.

Chen, Shuai; Liu, Zhengtang; Feng, Liping; Che, Xingsen; Zhao, Xiaoru

2013-09-01

353

Efficient diode-pumped Yb:Gd2SiO5 laser  

NASA Astrophysics Data System (ADS)

An efficient diode-pumped laser was demonstrated by using an ytterbium-doped laser crystal, Yb:Gd2SiO5 (Yb:GSO), wherein Yb3+ ions exhibit the largest ground-state splitting among all the ytterbium-doped crystals. The Yb:GSO laser can be operated at a low pumping threshold, and the most efficient laser occurs around 1088 nm since the corresponding emission band has the largest emission cross section and the lowest thermal population. A slope efficiency of 75% was demonstrated for a continuous-wave Yb:GSO laser at 1094 nm, and self-pulsed lasers were achieved within the tunable range of 1091-1105 nm, which are the longest laser wavelengths achieved for Yb3+ lasers.

Li, Wenxue; Pan, Haifeng; Ding, Liang'en; Zeng, Heping; Lu, Wei; Zhao, Guangjun; Yan, Chengfeng; Su, Liangbi; Xu, Jun

2006-05-01

354

Energy transfer mechanism in Yb 3+:Er 3+-ZBLAN: macro- and micro-parameters  

Microsoft Academic Search

Dynamics of forward energy transfer and backward energy transfer processes in fluorozirconate glass doubly doped with Yb3+ and Er3+ have been explained by “rate equation” and “fluorescence transfer function” models. From the rate equation analysis, macroscopic energy transfer parameters, the cross-relaxation coefficients, were determined to be 1.36×10?17 and 3.38×10?17s?1cm3 for the forward energy transfer (Yb3+?Er3+) and the backward transfer (Er3+?Yb3+),

Z. Meng; K. Nagamatsu; M. Higashihata; Y. Nakata; T. Okada; Y. Kubota; N. Nishimura; T. Teshima; S. Buddhudu

2004-01-01

355

Upconversion luminescence of monodisperse CaF2:Yb(3+)/Er(3+) nanocrystals.  

PubMed

Monodispersed CaF(2):Yb(3+)/Er(3+) nanocrystals have been prepared via a facile wet chemical technology. The upconversion luminescence properties of CaF(2):Yb(3+)/Er(3+) nanocrystals were compared with those of NaYF(4):Yb(3+)/Er(3+) nanocrystals with different phases and particle sizes. The results indicated that CaF(2) is a promising host material for producing desirable upconversion luminescence. PMID:19775118

Wang, Guofeng; Peng, Qing; Li, Yadong

2009-10-14

356

Electron-spectroscopy study of YbXCu4 (X=Ag,Au,Pd)  

NASA Astrophysics Data System (ADS)

We have studied the electronic structure of the heavy-electron compounds YbXCu4, with X =e/rAg,Au,Pd, using x-ray photoemission and bremsstrahlung isochromat spectroscopies. Consistent with other evidence of small Kondo temperatures, we find that Yb in this system is nearly trivalent and that Kondo features in the Yb 4f BIS spectra are either absent or weak.

Kang, J.-S.; Allen, J. W.; Rossel, C.; Seaman, C. L.; Maple, M. B.

1990-03-01

357

Laser-induced bulk damage in Yb:S-FAP crystals  

NASA Astrophysics Data System (ADS)

The Mercury laser uses ytterbium-doped strontium fluorapatite (Yb:S-FAP) crystals as the gain medium with a nominal clear aperture of 4 x 6 cm. Recent damage test data have indicated the existence of bulk precursors in Yb:S-FAP that initiate damage starting at approximately 10 J/cm2 at 9 ns under 1064 nm irradiation. In this paper, we report on preliminary results on bulk damage studies on Yb:S-FAP crystals.

Liao, Zhi M.; Adams, John J.; Jarboe, Jeff; Menapace, Joe; Nielsen, Norm; Schrauth, Sam; Wolfe, Justin; Erlandson, Al; Schaffers, Kathleen; Stolz, Christopher; Bayramian, Andy; Carid, John

2007-01-01

358

Phase equilibria and ordering in the system HfO 2 Yb 2 O 3  

Microsoft Academic Search

The system HfO2-Yb2O3 was investigated in the 0 to 100 mol % Yb2O3 range using X-ray diffraction analysis, linear thermal expansion measurements and melting point studies. At high temperatures, the system is dominated by wide regions of solid solutions based on HfO2 and Yb2O3 separated by a two-phase field which appears to extend to the solidus. The extent of the

P. Duran; C. Pascual

1984-01-01

359

Primary gamma transitions in 173,174Yb in neutron capture at isolated resonances  

Microsoft Academic Search

Gamma transitions in 174Yb were investigated in radiative neutron capture at 23 isolated and additional 7 partially resolved summed resonances of 173Yb. The time-of-flight technique was used on an enriched target at the IBR-30 reactor at JINR Dubna. A total of 77 primary gamma transitions are reported populating levels in 174Yb up to 2.8 MeV in the spin–parity range 1±,2±,3±,4±.

S. A. Telezhnikov; C. Granja; H. T. Hiep; J. Honzátko; M. Králík; M.-E. Montero-Cabrera; S. Pospísil

2005-01-01

360

Compositional investigation of YB(3+)-doped glasses for laser-induced fluorescent cooling applications  

Microsoft Academic Search

In this work, a compositional analysis of Yb3+-doped glasses and transparent glass-ceramics was undertaken to determine potential hosts for use in the development of a first-generation optical cryocooler for space-borne remote sensing applications. By pumping to the lower levels of the Yb 3+ 2F5\\/2 manifold, followed by a thermally-driven population redistribution to higher levels within both manifolds of Yb 3+,

Michael Thomas Murtagh

1999-01-01

361

Laser properties of Yb{sup 3+}-doped Srâ(POâ)âF crystals  

Microsoft Academic Search

Yb{sup 3+} based lasers have received substantial attention over the past several years. Yb-based materials, which typically lase around 1 μm, are aided by the simple electronic structure of Yb{sub 3+} in that it has only two accessible electronic states eliminating the detrimental impact of upconversion or excited state absorption. In addition, the inherently small quantum defect of â¼10--15% has

C. D. Marshall; S. A. Payne; L. K. Smith; K. I. Schaffers; R. Beach; M. Emanuel; H. T. Powell; W. F. Krupke; B. H. T. Chai

1994-01-01

362

Charge Fluctuations and the Valence Transition in Yb under Pressure  

SciTech Connect

We present a dynamical mean field theory study of the valence transition (f{sup 14} {yields} f{sup 13}) in elemental, metallic Yb under pressure. Our calculations reproduce the observed valence transition as reflected in the volume dependence of the 4f occupation. The transition is accelerated by heating, and suggests quasiparticle or Kondo-like structure in the spectra of the trivalent end state, consistent with the early lanthanides. Results for the local charge fluctuations and susceptibility, however, show novel signatures uniquely associated with the valence transition itself, indicating that Yb is a fluctuating valence material in contrast to the intermediate valence behavior seen in the early trivalent lanthanides Ce, Pr, and Nd.

Ylvisaker, E R; Kunes, J; McMahan, A K; Pickett, W E

2009-04-21

363

XRD and IR Studies of Yb3+ Doped Tellurite Glass  

NASA Astrophysics Data System (ADS)

Ytterbium doped sodium-tellurite glasses having composition of (80-x) TeO2-20Na2O-(x)Yb2O3 (where x = 0.0-2.0 mol%) are prepared by melt quenching technique. The crystallinity of the glass has been examined using X-ray diffraction technique. All glass are found to be amorphous in nature. Meanwhile the transmission spectroscopy is determine by using Infrared Spectroscopy. It is found that the absorption vibrational spectra occurs at range 3405-3423 cm-1, 1632-1643 cm-1, 1377-1382 cm-1, 721-732 cm-1 and 589-606 cm-1 peaks. The predominant peaks around 700 cm-1 is due to the Te-O-Te vibration while peak at 600 cm-1 is due to the vibration of Yb3+ ions.

Sahar, M. R.; Isa, H. Noor

2011-03-01

364

Passively Q-switched eyesafe Yb:Er:glass laser  

NASA Astrophysics Data System (ADS)

In this paper, pulsed operation of the 980 nm diode-pumped Yb:Er:glass solid-state-laser operating at 1543 nm using Co:Spinel saturable absorber is described. The Yb:Er:glass gain medium was end-pumped using a 10 W fiber-coupled 980 nm laser diode. Passively q-switched laser operation was accomplished for both CW and quasi-CW operations. Up to 2 mm thick uncoated Co:Spinel samples were used for our tests. With quasi-CW pumping, pulsewidths greater than 20 ns, pulse energies of greater than 250 ?J and free-running PRFs up to 1.2 kHz have been demonstrated. So far, up to 3 % optical-to-optical efficiency has been achieved with uncoated q-switch materials. Currently, this laser is being developed for pumping a long-wave IR (8-12 ?m) optical parametric oscillator for use in spectrapolarimetric applications.

Prasad, Narasimha S.; Urbina, Chris J.; Tousley, Bradford C.; Shori, Ramesh K.; Stone-Sundberg, Jennifer L.; Kokta, Milan R.

2004-07-01

365

Spectroscopy of ^161Yb with ATLAS/Gammasphere  

NASA Astrophysics Data System (ADS)

An experiment was performed at Argonne National Laboratory's ATLAS accelerator using the Gammasphere array (˜100 HPGe detectors) whose primary aim was to investigate the collective bands beyond band termination in ^160Yb via the ^120Sn(^44Ca,4n) fusion-evaporation reaction. The high spin yield of the 4n channel was enhanced significantly by selecting a beam energy of 222 MeV and a considerable amount of data of 3n and 5n channels were also obtained. Here is presented the preliminary result of an initial spectroscopic analysis of ^161Yb, the product of the 3n channel. The RadWare (coincidence analysis) software package was utilized and the possibility of revised level placements has been suggested by the analysis, in comparison with previous level schemes.

Gaison, J.; Carroll, J.; Litz, M.; Wang, X.; Riley, M.; Baron, J.; Miller, S.; Simpson, J.; Paul, E.; Boston, A.; Boston, H.; Nolan, J.; Rees, M.; Revill, J.; Janssens, R.; Carpenter, M.; Kondev, F.; Lauritsen, T.; Zhu, S.; Riedinger, L.; Hartley, D.; Ayangeakaa, A.; Garg, U.; Chiara, C.

2012-10-01

366

Photodarkening-Induced Absorption and Fluorescence Changes in Yb Fibers  

NASA Astrophysics Data System (ADS)

We study the photodarkening effect in a double clad ytterbium-doped silica fiber fabricated by modified chemical vapor deposition and solution doping. A common measurement technology for photodarkening is used to study the photodarkening-induced absorption spectra. We present a fast and simple method to observe the PD effect by measurement of the fluorescence spectra. The method proposed here can be used to observe the influence for a short time, and thus reduces the requirements of system stability and heat management. It is obtained that under the condition of 45.5% Yb ion inversion level, photodarkening-induced excessive loss at an equilibrium state is above 4.5dB/m and florescence intensity degradation is above 10% after 500min pumping at 1041 nm for the home-made normal Yb/Al co-doped silica fiber.

Chen, Gui; Xie, Lu; Wang, Yi-Bo; Zhao, Nan; Li, Hai-Qing; Jiang, Zuo-Wen; Peng, Jing-Gang; Yang, Lü-Yun; Dai, Neng-Li; Li, Jin-Yan

2013-10-01

367

Graphene mode-locked femtosecond Yb:KLuW laser  

NASA Astrophysics Data System (ADS)

Large-area monolayer graphene, synthesized by chemical vapor deposition, was transferred to a 1-in. quartz substrate. The high-quality monolayer graphene has been subject to characterization of the nonlinear properties near 1 ?m and was successfully applied as saturable absorber for passive mode-locking of a femtosecond Yb:KLuW laser. The diode-pumped mode-locked Yb:KLuW laser was tunable around 1.04 ?m and delivered pulses as short as 160 fs. The maximum output power of 160 mW was demonstrated for 203 fs pulse duration. The mode-locked laser results are comparable to those demonstrated with the same laser gain medium using single-walled carbon nanotubes as saturable absorbers.

Ugolotti, Elena; Schmidt, Andreas; Petrov, Valentin; Wan Kim, Jun; Yeom, Dong-Il; Rotermund, Fabian; Bae, Sukang; Hee Hong, Byung; Agnesi, Antonio; Fiebig, Christian; Erbert, Götz; Mateos, Xavier; Aguiló, Magdalena; Diaz, Francesc; Griebner, Uwe

2012-10-01

368

Further Considerations of the Ce\\/Yb vs. Ba\\/Ce Plot in Volcanology and Tectonics  

Microsoft Academic Search

A plot of Ce\\/Yb vs. Ba\\/Ce, for locality averages, effectively separates mid-ocean ridge basalts (MORB) (Ce\\/Yb <10, Ba\\/Ce 1-4.2), oceanic island volcanics (OIV) (Ce\\/Yb >10, Ba\\/Ce <6), which are generally hotspot related, and island arc volcanics (IAV) (Ce\\/Yb <23, Ba\\/Ce >4.2). The conventional interpretation is that these three types of volcanic environments involve oceanic rift-related, large-volume partial melts (˜20-30%) of

Bruce R. Doe

2002-01-01

369

Refinement of Eutectic Si Phase in Al-5Si Alloys with Yb Additions  

NASA Astrophysics Data System (ADS)

A series of Al-5 wt pct Si alloys with Yb additions (up to 6100 ppm) have been investigated using thermal analysis and multiscale microstructure characterization techniques. The addition of Yb was found to cause no modification effect to a fibrous morphology involving Si twinning; however, a refined plate-like eutectic structure was observed. The Al2Si2Yb phase was observed with Yb addition level of more than 1000 ppm. Within the eutectic Al and Si phases, the Al2Si2Yb phase was also found as a precipitation from the remained liquid. No Yb was detected in the ?-Al matrix or plate-like Si particle, even with Yb addition up to 6100 ppm. The absence of Yb inside the eutectic Si particle may partly explain why no significant Si twinning was observed along {111}Si planes in the eutectic Si particle. In addition, the formation of the thermodynamic stable YbP phases is also proposed to deteriorate the potency of AlP phase in Al alloys. This investigation highlights to distinguish the modification associated with the ever present P in Al alloys. We define modification as a transition from faceted to fibrous morphology, while a reduction of the Si size is termed refinement.

Li, J. H.; Suetsugu, S.; Tsunekawa, Y.; Schumacher, P.

2013-02-01

370

Measurement of high-photodarkening resistance in phosphate fiber doped with 12% Yb2O3  

NASA Astrophysics Data System (ADS)

We report the measurement of photodarkening in single-mode phosphate fibers with a Yb3+ concentrations of 7.1 × 1026 m-3 and 1.42 × 1027 m-3 (6 wt.% and 12 wt.% Yb2O3).We compare the photodarkening resistance of these phosphate fibers with that of three single-mode Yb3+-doped silica fibers. Our data shows that under strong pumping conditions, phosphate fibers allow Yb3+ concentrations that are least 6 times greater than the most photodarkening-resistant silica fibers to date without the onset of photodarkening at 660 nm.

Lee, Y. W.; Sinha, S.; Digonnet, M. J. F.; Byer, R. L.; Jiang, S.

2008-03-01

371

Specific heat of mixed valence system YbInCu4 under pressure  

NASA Astrophysics Data System (ADS)

We have carried out the measurement of specific heat under hydrostatic pressure P up to 0.68GPa on YbInCu4, which undergoes a first-order valence transition at TV~40K. With increasing P, TV decreases with the slope of ?TV/?P=-16.2K/GPa, and the value of excess entropy ?S due to the valence transition increases slightly. If ?S originates from the mixing Yb3+ and Yb2+ ions, the experimental result can be understood as the decrease of hole occupation number nf in the 4f shell of Yb in the low-temperature phase by pressurization.

Ito, M.; Sakamoto, S.; Asada, K.; Fujita, T.; Kojima, K.; Hiraoka, K.; Suzuki, T.

2004-05-01

372

X-RAY ABSORPTION SPECTROSCOPY OF YB3+-DOPED OPTICAL FIBERS  

SciTech Connect

Optical fibers doped with Ytterbium-3+ have become increasingly common in fiber lasers and amplifiers. Yb-doped fibers provide the capability to produce high power and short pulses at specific wavelengths, resulting in highly effective gain media. However, little is known about the local structure, distribution, and chemical coordination of Yb3+ in the fibers. This information is necessary to improve the manufacturing process and optical qualities of the fibers. Five fibers doped with Yb3+ were studied using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and X-ray Absorption Near Edge Spectroscopy (XANES), in addition to Yb3+ mapping. The Yb3+ distribution in each fiber core was mapped with 2D and 1D intensity scans, which measured X-ray fluorescence over the scan areas. Two of the five fibers examined showed highly irregular Yb3+ distributions in the core center. In four of the five fibers Yb3+ was detected outside of the given fiber core dimensions, suggesting possible Yb3+ diffusion from the core, manufacturing error, or both. X-ray absorption spectroscopy (XAS) analysis has so far proven inconclusive, but did show that the fibers had differing EXAFS spectra. The Yb3+ distribution mapping proved highly useful, but additional modeling and examination of fiber preforms must be conducted to improve XAS analysis, which has been shown to have great potential for the study of similar optical fi bers.

Citron, Robert; Kropf, A.J.

2008-01-01

373

Greening EU Studies: An Academic Manifesto  

Microsoft Academic Search

This article responds to Ian Manners' challenge to scholars of EU studies to engage with a broader range of theoretical perspectives and projects than is conventional. Specifically, it investigates the benefits of such an epistemological shift as that called for by Manners, critiquing the condition of the mainstream in EU studies—which is still somewhat unreflexively defined by dominant norms of

Alex Warleigh-Lack

2012-01-01

374

Social Models in the Enlarged EU  

Microsoft Academic Search

This paper considers the impact of the developments of the last 20 years on the nature of social models in the EU as categorized by the traditional Anglo-Saxon, Continental, Nordic and Southern regimes. It looks in particular at the impact of enlargement, globalisation and the pressures within the EU for harmonisation. In order to consider whether the addition of the

David G. Mayes; Zaidah Mustaffa

2010-01-01

375

EU fuel cycle development priorities for ITER  

Microsoft Academic Search

The paper describes the key elements of the EU fuel cycle development for ITER. The programme is now closely focused on the systems allocated to the EU for in-kind supply. These include the isotope separation and water detritiation systems (ISS and WDS) and the cryopumps for torus exhaust, neutral beam injectors (NBI) and cryostat pumping. For all of these systems,

D. Murdoch; I. Cristescu; C. Day; M. Glugla; R. Laesser; A. Mack

2007-01-01

376

Electronic structure of Kondo lattice compounds YbNi3X9 (X = Al, Ga) studied by hard x-ray spectroscopy  

NASA Astrophysics Data System (ADS)

We have performed hard x-ray photoemission spectroscopy (HAXPES) for Yb-based Kondo lattice compounds; an antiferromagnetic heavy-fermion system YbNi3Al9 and a valence fluctuation system YbNi3Ga9. The Yb 3d5/2 spectra of YbNi3Ga9 showed both Yb2+ and Yb3+-derived structures indicating strong valence fluctuation, and the intensity of Yb2+ (Yb3+) structures gradually increased (decreased) on cooling. The Yb 3d5/2 spectra of YbNi3Al9 mostly consisted of Yb3+-derived structures and showed little temperature dependence. The Yb valences of YbNi3Ga9 and YbNi3Al9 at 22 K were evaluated to be 2.43 and 2.97, respectively. Based on the results of the Ni 2p and valence-band HAXPES spectra together with soft x-ray valence-band spectra, we described that the difference of physical properties of YbNi3X9 (X= Al, Ga) is derived from the differences of the 4f-hole level relative to the Fermi level (EF) and Ni 3d density of states at EF. The HAXPES results on the Yb valences were consistent with those obtained by x-ray absorption spectroscopy using the partial fluorescence yield mode and resonant x-ray emission spectroscopy at the Yb L3 edge.

Utsumi, Yuki; Sato, Hitoshi; Ohara, Shigeo; Yamashita, Tetsuro; Mimura, Kojiro; Motonami, Satoru; Shimada, Kenya; Ueda, Shigenori; Kobayashi, Keisuke; Yamaoka, Hitoshi; Tsujii, Naohito; Hiraoka, Nozomu; Namatame, Hirofumi; Taniguchi, Masaki

2012-09-01

377

K = 0 rotational bands in ¹⁷⁴Yb  

Microsoft Academic Search

The gamma deexcitation of three excited K=O rotational bands has been ; studied following population in the ¹⁷³Yb(n, gamma ) reaction at resonant ; neutron energies of 4.53 and 17.7 eV. The gamma rays were detected in singles ; and coincidence with Ge(Li) detectors. Analysis was also made of the primary ; radiation. The decay properties of these bands cxhibit

R. F. Casten; D. Breitig; W. R. Kane; S. F. Mughabghab

1973-01-01

378

Spectroscopic and lasing properties of disordered Yb 3+ -doped crystals  

Microsoft Academic Search

The luminescence properties and luminescence decay kinetics of disordered Yb3+-doped crystals of various oxides are investigated and the possibility of their use as active laser media in the near-IR region\\u000a (in the vicinity of 1 µm) under laser diode pumping is established. Three groups of disordered oxide crystals were analyzed:\\u000a calcium niobium gallium garnet, yttrium-stabilized zirconia, and double tungstates andmolybdates

V. E. Shukshin

2009-01-01

379

Accelerated Reader[TM]. What Works Clearinghouse Intervention Report  

ERIC Educational Resources Information Center

|"Accelerated Reader"[TM] is a guided reading intervention used to supplement regular reading instruction in K-12 classrooms. Its aim is to improve students' reading skills through reading practice and quizzes on the books students read. The "Accelerated Reader"[TM] program calls for students to select and read a book and then take a computerized…

What Works Clearinghouse, 2010

2010-01-01

380

Social Stories[TM] for Children with Disabilities  

ERIC Educational Resources Information Center

|A review of the empirical research literature on Social Stories[TM] is presented, including a descriptive review and single-subject meta-analysis of appropriate studies. Examination of data suggests the effects of Social Stories[TM] are highly variable. Interpretations of extant studies are frequently confounded by inadequate participant…

Reynhout, Georgina; Carter, Mark

2006-01-01

381

Full Immersive Virtual Environment Cave[TM] in Chemistry Education  

ERIC Educational Resources Information Center

|By comparing two-dimensional (2D) chemical animations designed for computer's desktop with three-dimensional (3D) chemical animations designed for the full immersive virtual reality environment CAVE[TM] we studied how virtual reality environments could raise student's interest and motivation for learning. By using the 3ds max[TM], we can…

Limniou, M.; Roberts, D.; Papadopoulos, N.

2008-01-01

382

Radiometric comparison of the LANDSAT5 TM and MSS sensors  

Microsoft Academic Search

This paper analyses the radiometric accuracy of LANDSAT-5 Thematic Mapper (TM) data and of LANDSAT-5 Multispectral Scanner (MSS) data, using concurrent TM and MSS images recorded simultaneously over the city of Montreal, Quebec, Canada. The data sets were obtained from the Canada Centre for Remote Sensing (CCRS), and have been preprocessed for geometric correction, and for radiometric 23calibration utilizing the

ALAIN ROYER; RICHARD BROCHU; JENNIFER M. MURPHY; PHILIPPE M. TEILLET

1987-01-01

383

Full Immersive Virtual Environment Cave[TM] in Chemistry Education  

ERIC Educational Resources Information Center

By comparing two-dimensional (2D) chemical animations designed for computer's desktop with three-dimensional (3D) chemical animations designed for the full immersive virtual reality environment CAVE[TM] we studied how virtual reality environments could raise student's interest and motivation for learning. By using the 3ds max[TM], we can visualize…

Limniou, M.; Roberts, D.; Papadopoulos, N.

2008-01-01

384

LogTM: log-based transactional memory  

Microsoft Academic Search

Transactional memory (TM) simplifies parallel program- ming by guaranteeing that transactions appear to execute atomically and in isolation. Implementing these properties includes providing data version management for the simul- taneous storage of both new (visible if the transaction com- mits) and old (retained if the transaction aborts) values. Most (hardware) TM systems leave old values \\

Kevin E. Moore; Jayaram Bobba; Michelle J. Moravan; Mark D. Hill; David A. Wood

2006-01-01

385

Optically active centers in Eu implanted, Eu in situ doped GaN, and Eu doped GaN quantum dots  

Microsoft Academic Search

A comparison is presented between Eu implanted and Eu in situ doped GaN thin films showing that two predominant Eu sites are optically active around 620 nm in both types of samples with below and above bandgap excitation. One of these sites, identified as a Ga substitutional site, is common to both types of Eu doped GaN samples despite the

L. Bodiou; A. Braud; J.-L. Doualan; R. Moncorgé; J. H. Park; C. Munasinghe; A. J. Steckl; K. Lorenz; E. Alves; B. Daudin

2009-01-01

386

Laser excited long lasting luminescence in CaAl?O?: Eu³?/Eu²?+Nd³? phosphor.  

PubMed

The europium and neodymium oxides doped nano-structured calcium aluminate phosphor samples have prepared through combustion technique and their luminescence properties are studied using laser excitations. Samples prepared in open atmosphere showed the presence of both Eu(3+) and Eu(2+) states and their ratio changes with calcination temperature. Single Eu(3+)/Eu(2+) ions doped sample has found to give broad emission at 450 nm without the persistence glow while the Eu(3+)+Nd(3+) ions codoped sample has shown persistence glow at 450 nm (Eu(2+)) on 355 nm laser excitation. Wavelength selective excitations show that 266 nm excitation gives the intense emissions from both Eu(3+) and Eu(2+) states with no afterglow but 355 nm excitation gives negligible emission from Eu(3+) ions and a strong afterglow at 450 nm wavelength. The mechanism of wavelength dependent phosphorescence has been discussed. Studies on Stark splittings and their relative intensities in emission spectra of Eu(3+) ions have shown that Eu(3+) ion can be used as excellent probe of crystal structure. PMID:23220659

Kumar, K; Singh, A K; Rai, S B

2012-10-13

387

Distribution of 152Eu and 154Eu in the 'alluvial soil-rhizosphere-plant roots' system.  

PubMed

Accumulation of (152)Eu and (15)(4)Eu isotopes in bulk soil and rhizosphere soil in the near-field zone of influence of the Krasnoyarsk Mining and Chemical Combine was studied. An uneven distribution of specific activity of Eu isotopes was observed, with the gross specific activities of the isotopes in the bulk soil exceeding those of the rhizosphere. In the most contaminated locations the fine and the coarse granulometric fractions are enriched with the isotopes. A laboratory experiment indicated potential removal of soluble Eu isotopes by river flood waters may amount to 3% of the total Eu in both bulk and rhizosphere soils. The root system of plants growing in the contaminated territory accumulates (152)Eu and (154)Eu, although the isotopes were not discovered in aboveground parts of plants. Root-hairs were found to be the most contaminated. PMID:22305001

Kropatcheva, Marya; Chuguevsky, Alexei; Melgunov, Mikhail

2011-12-06

388

Phase stability of AlYB14 sputtered thin films  

NASA Astrophysics Data System (ADS)

AlYB14 (Imma) thin films were synthesized by magnetron sputtering. On the basis of x-ray diffraction, no phases other than crystalline AlYB14 could be identified. According to electron probe microanalysis, energy dispersive x-ray analysis and elastic recoil detection analysis, the Al and Y occupancies vary in the range of 0.73-1.0 and 0.29-0.45, respectively. Density functional theory based calculations were carried out to investigate the effect of occupancy on the stability of AlxYyB14 (x,y = 0.25, 0.5, 0.75, 1). The mean effective charge per icosahedron and the bulk moduli were also calculated. It is shown that the most stable configuration is Al0.5YB14, corresponding to a charge transfer of two electrons from the metal atoms to the boron icosahedra. Furthermore, it is found that the stability of a configuration is increased as the charge is homogeneously distributed within the icosahedra. The bulk moduli for all configurations investigated are in the range between 196 and 220 GPa, rather close to those for known hard phases such as ?- Al2O3.

Kölpin, Helmut; Music, Denis; Henkelman, Graeme; Emmerlich, Jens; Munnik, Frans; Schneider, Jochen M.

2009-09-01

389

Survey of the phase formation in the Yb2O3Ga2O3MO and Yb2O3Cr2O3MO systems in air at high temperatures (M: Co, Ni, Cu, and Zn)  

Microsoft Academic Search

The phase relations in the Yb2O3-Ga2O3-CoO system at 1300 and 1200°C, the Yb2O3-Ga2O3-NiO system at 1300 and 1200°C, the Yb2O3-Ga2O3-CuO system at 1000°C and the Yb2O3-Ga2O3-ZnO system at 1350 and 1200°C, the Yb2O3-Cr2O3-CoO system at 1300 and 1200°C, the Yb2O3-Cr2O3-NiO system at 1300 and 1200°C, the Yb2O3-Cr2O3-CuO system at 1000°C, and the Yb2O3-Cr2O3-ZnO system at 1300 and 1200°C were determined

Noboru Kimizuka; Eiji Takayama

1982-01-01

390

Factors governing Yb magnetism in Yb0.95PtIn2 and other MgCuAl2-type structures  

NASA Astrophysics Data System (ADS)

The ternary compound “YbPtIn2” has been synthesized and its crystal structure determined using single crystal X-ray diffraction techniques. The compound crystallizes in the MgCuAl2 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 (#63) with lattice parameters of a=4.3410(1) Å, b=10.3230(2) Å, and c=7.8510(2) Å. 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 Yb0.95PtIn2. Magnetic and resistivity measurements reveal that “YbPtIn2” is a weakly interacting, non-magnetic metal exclusively containing Yb2+, and with a resistivity (?) varying from 34 ?? cm at room temperature to a residual resistivity ?0 of 23 ?? 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 Yb3+ and potentially induce heavy fermion behavior.

Malingowski, Andrew C.; Kim, Moosung; Liu, Jue; Wu, Liusuo; Aronson, Meigan C.; Khalifah, Peter G.

2013-02-01

391

Cooperative energy transfer and frequency upconversion in Yb3+-Tb 3+ and Nd 3+-Yb 3+-Tb 3+ codoped GdAl3(BO3)4 phosphors.  

PubMed

Polycrystalline GdAl(3)(BO(3))(4) phosphors co-doped with Yb(3+)/Tb(3+) and/or Nd(3+)/Yb(3+)/Tb(3+) have been synthesized by combustion method. Upon excitation with a 980 nm laser diode, an intense green upconversion luminescence has been observed in GdAl(3)(BO(3))(4):Yb,Tb phosphor. The quadratic dependence of the luminescence on the pump-laser power indicating a cooperative energy transfer process. Meanwhile, it is noticed that upon excitation with 808 nm laser diode, intense luminescence has clearly been detected in GdAl(3)(BO(3))(4):Nd,Yb,Tb phosphor. The luminescence intensity exhibits also a quadratic dependence on incident pump-laser power. However, no green-emission has been observed in GdAl(3)(BO(3))(4) phosphors co-doped with Yb(3+)/Tb(3+) or Nd(3+)/Tb(3+) respectively upon excited at 808 nm laser diode. A proposed upconversion mechanism involving energy transfer from Nd(3+) to Yb(3+), and then a cooperative energy transfer process from two excited Yb(3+) to Tb(3+) has been presented. PMID:17609865

Yang, C H; Pan, Y X; Zhang, Q Y; Jiang, Z H

2007-07-04

392

Autocapture TM - und Capture-Management TM Aktuelle Konzepte zur automatischen Reizschwellenmessung und Anpassung der Stimulationsamplitude  

Microsoft Academic Search

\\u000a Summary   Pacing threshold is not a stable value during the pacemaker‘s life. It is affected by many physiological, pharmacological\\u000a and pathophysiological factors. A pacing system able to confirm capture and automatically adjust its output to the actual\\u000a pacing threshold is highly desirable for a prolonged battery life and maximal patient safety. The AutocaptureTM of St. Jude Medical and the Capture

M. Anelli-Monti; H. Mächler; P. Oberwalder; D. Dacar; I. Knez; L. Salaymeh; Ch. Streinu; B. Rigler

2001-01-01

393

Long-Range Magnetic Ordering in Pyrochlore Iridate Eu2Ir2O7  

NASA Astrophysics Data System (ADS)

In the pyrochlore iridate Eu2Ir2O7 [1,,] Eu^3+ is nonmagnetic (L = S, J = 0) and S(Ir^4+) = 1/2 [1], so that it is a rare example of a frustrated S=1/2 pyrochlore. Spin-glass-like behavior at the metal-insulator transition (MIT) and no magnetic ordering down to 0.3 K have been reported for this compound [2,,]. We discuss ?SR measurements on Eu2Ir2O7 polycrystalline samples that yield strong evidence for long-range magnetic ordering. We observe well-defined muon spin precession frequencies below TM 120 K, consistent with the MIT temperature [2] but indicating long-range ordering instead of a spin-glass like transition. Significant dynamic muon spin relaxation persists to low temperatures, as is often the case in frustrated antiferromagnets. Work supported by NSF (U.S.), Grants 0801407 (UCR) and 0604105 (CSULA), and MEXT (Japan), Grants-in-Aid Nos. 17071003 and 19052003. [1] B. J. Kim et al., Phys. Rev.Lett. 101, 076402 (2008). [2] N. Taira et al., J. Phys.: Condens. Matter 13, 5527 (2001). [3] C. L. Chien and A. W. Sleight, Phys. Rev. B 18, 2031 (1978).

Zhao, S.; Mackie, J. M.; Maclaughlin, D. E.; Bernal, O. O.; Ohta, Y.; Nakatsuji, S.

2010-03-01

394

Comparison of Tm?:?ZBLAN and Tm?:?silica fiber lasers; Spectroscopy and tunable pulsed laser operation around 1.9 µm  

Microsoft Academic Search

Tm-doped ZBLAN and Tm-doped silica glass are compared spectroscopically and the fiber lasing of the Tm 3 F 4?? 3 H 6 transition around 1.9 µm in ZBLAN and silica fibers is compared. The spectroscopy of these materials indicates that Tm:ZBLAN possesses advantages over Tm:silica glass due to the lower phonon energies. The phonon energy in these glass hosts influences both

B. M. Walsh; N. P. Barnes

2004-01-01

395

Different roles of TM5, TM6, and ECL3 in the oligomerization and function of human ABCG2.  

PubMed

ABCG2 is a member of the ATP-binding cassette transporter superfamily, and its overexpression causes multidrug resistance (MDR) in cancer chemotherapy. ABCG2 may also protect cancer stem cells by extruding cytotoxic materials. ABCG2 has previously been shown to exist as a high-order homo-oligomer consisting of possibly 8-12 subunits, and the oligomerization domain was mapped to the C-terminal domain, including TM5, ECL3, and TM6. In this study, we further investigate this domain in detail for the role of each segment in the oligomerization and drug transport function of ABCG2 using domain swapping and site-directed mutagenesis. We found that none of the three segments (TM5, TM6, and ECL3) is essential for the oligomerization activity of ABCG2 and that any one of these three segments in the full-length context is sufficient to support ABCG2 oligomerization. While TM5 plays an important role in the drug transport function of ABCG2, TM6 and ECL3 are replaceable. Thus, each segment in the TM5-ECL3-TM6 domain plays a distinctive role in the oligomerization and function of ABCG2. PMID:22497316

Mo, Wei; Qi, Jing; Zhang, Jian-Ting

2012-04-19

396

Performance of a minimally invasive uncalibrated cardiac output monitoring system (FlotracTM\\/VigileoTM) in haemodynamically unstable patients  

Microsoft Academic Search

Background. Early haemodynamic assessment is of particular importance in the evaluation of haemodynamically compromised patients, but is often precluded by the invasiveness and com- plexity of the established cardiac output (CO) monitoring techniques. The FloTrac TM \\/Vigileo TM system allows minimally invasive CO determination based on the arterial pressure waveform derived from any standard arterial catheter, and the algorithm underlying

F. D. Compton; B. Zukunft; C. Hoffmann; W. Zidek; J.-H. Schaefer

2008-01-01

397

Temperature-dependent lasing and spectroscopy of Yb:Y 2O 3 and Yb:Sc 2O 3  

Microsoft Academic Search

Spectroscopic and laser properties of Yb3+ in ceramic Y2O3 have been studied at room and cryogenic temperatures. Laser performance is very substantially improved by cooling to liquid nitrogen temperature, primarily due to the great reduction in ground state absorption that permits laser operation on the much stronger 1030-nm emission line rather than the 1077-nm line. The 976-nm “zero line” is

Larry D. Merkle; G. Alex Newburgh; Nikolay Ter-Gabrielyan; Arockiasamy Michael; Mark Dubinskii

2008-01-01

398

Synthesis of YbyCo4Sb12/Yb2O3 composites and their thermoelectric properties  

NASA Astrophysics Data System (ADS)

Composites containing Yb-filled CoSb3 and well-distributed Yb2O3 particles are synthesized by in situ reaction method. The structural, chemical, and transport properties of the composites are studied. Some Yb2O3 particles with microsize locate at the grain boundaries of matrix and others distribute within YbyCo4Sb12 grains as nanoscale inclusions. The combination of the ``rattling'' of Yb ions inside the voids of CoSb3 and the phonon scattering of the oxide defects results in a remarkable reduction in the lattice thermal conductivity. The thermoelectric performance of the composites is significantly improved, and the maximum figures of merit reach 1.3 for the Yb0.25Co4Sb12/Yb2O3 and 1.2 for the Yb0.21Co4Sb12/Yb2O3 composites at 850 K.

Zhao, X. Y.; Shi, X.; Chen, L. D.; Zhang, W. Q.; Bai, S. Q.; Pei, Y. Z.; Li, X. Y.; Goto, T.

2006-08-01

399

YB-1 is a Transcription/Translation Factor that Orchestrates the Oncogenome by Hardwiring Signal Transduction to Gene Expression  

PubMed Central

The Y-box Binding Protein-1 (YB-1) is a highly conserved oncogenic transcription/translation factor that is expressed in cancers affecting adults and children. It is now believed that YB-1 plays a causal role in the development of cancer given recent work showing that its expression drives the tumorigenesis in the mammary gland. In human breast cancers, YB-1 is associated with rapidly proliferating tumors that are highly aggressive. Moreover, expression of YB-1 promotes the growth of breast cancer cell lines both in monolayer and anchorage independent conditions. The involvement of YB-1 in breast cancer pathogenesis has made it a putative therapeutic target; however, the mechanism(s) that regulate YB-1 are poorly understood. This review first describes the oncogenic properties of YB-1 in cancer. It also highlights the importance of YB-1 in hardwiring signal transduction pathways to the regulation of genes involved in the development of cancer.

Wu, Joyce; Stratford, Anna L.; Astanehe, Arezoo; Dunn, Sandra E.

2007-01-01

400

Visible to infrared energy conversion in Pr3+-Yb3+ co-doped fluoroindate glasses  

NASA Astrophysics Data System (ADS)

Processes involving visible to infrared energy conversion are presented for Pr3+-Yb3+ co-doped fluoroindate glasses. The emission in the visible and infrared regions, the luminescence decay time of the Pr3+:3P0 ? 3H4 (482 nm), Pr3+:1D2 ? 3H6 (800 nm), Yb3+:2F5/2 ? 2F7/2 (1044 nm) transitions and the photoluminescence excitation spectra were measured in Pr3+ samples and in Pr3+-Yb3+ samples as a function of the Yb3+ concentration. In addition, energy transfer efficiencies were estimated from Pr3+:3P0 and Pr3+:1D2 levels to Yb3+:2F7/2 level. Down-Conversion (DC) emission is observed due to a combination of two different processes: 1-a one-step cross relaxation (Pr3+:3P0 ? 1G4; Yb3+:2F7/2 ? 2F5/2) resulting in one photon emitted by Pr3+ (1G4 ? 3H5) and one photon emitted by Yb3+ (2F7/2 ? 2F5/2); 2-a resonant two-step first order energy transfer, where the first part of energy is transferred to Yb3+ neighbor through cross relaxation (Pr3+:3P0 ? 1G4; Yb3+:2F7/2 ? 2F5/2) followed by a second energy transfer step (Pr3+:1G4 ? 3H4; Yb3+:2F7/2 ? 2F5/2). A third process leading to one IR photon emission to each visible photon absorbed involves cross relaxation energy transfer (Pr3+:1D2 ? 3F4; Yb3+:2F7/2 ? 2F5/2).

Borrero-González, L. J.; Galleani, G.; Manzani, D.; Nunes, L. A. O.; Ribeiro, S. J. L.

2013-10-01

401

Prognostic Association of YB-1 Expression in Breast Cancers: A Matter of Antibody  

PubMed Central

The literature concerning the subcellular location of Y-box binding protein 1 (YB-1), its abundance in normal and cancer tissues, and its prognostic significance is replete with inconsistencies. An explanation for this could be due in part to the use of different antibodies in immunohistochemical and immunofluorescent labeling of cells and tissues. The inconsistencies could also be due to poor resolution of immunohistochemical data. We analyzed two cohorts of breast tumours for both abundance and subcellular location of YB-1 using three different antibodies; two targeting N-terminal epitopes (AB-a and AB-b) and another (AB-c) targeting a C-terminal epitope. We also investigated stress-induced nuclear translocation of YB-1 in cell culture. We report that both AB-a and AB-c detected increased YB-1 in the cytoplasm of high-grade breast cancers, and in those lacking estrogen and progesterone receptors; however the amount of YB-1 detected by AB-a in these cancers is significantly greater than that detected by AB-c. We confirm our previously published findings that AB-b is also detecting hnRNP A1, and cannot therefore be used to reliably detect YB-1 by immunohistochemistry. We also report that AB-a detected nuclear YB-1 in some tumour tissues and stress treated cells, whereas AB-c did not. To understand this, cancer cell lines were analyzed using native gel electrophoresis, which revealed that the antibodies detect different complexes in which YB-1 is a component. Our data suggest that different YB-1 antibodies show different staining patterns that are determined by the accessibility of epitopes, and this depends on the nature of the YB-1 complexes. It is important therefore to standardize the protocols if YB-1 is to be used reproducibly as a prognostic guide for different cancers.

Woolley, Adele G.; Algie, Michael; Samuel, Weini; Harfoot, Rhodri; Wiles, Anna; Hung, Noelyn A.; Tan, Puay-Hoon; Hains, Peter; Valova, Valentina A.; Huschtscha, Lily; Royds, Janice A.; Perez, David; Yoon, Han-Seung; Cohen, Scott B.; Robinson, Phillip J.; Bay, Boon-Huat; Lasham, Annette; Braithwaite, Antony W.

2011-01-01

402

High-gain amplification in Yb:CaF2 crystals pumped by a high-brightness Yb-doped 976 nm fiber laser  

NASA Astrophysics Data System (ADS)

We report on high single-pass gain in Yb:CaF2 crystal longitudinally pumped with a 40 W high-brightness fiber laser source based on an ytterbium-doped ultra-large core photonic crystal rod-type fiber operating at 976 nm. A single-pass small-signal gain of 3.2 has been achieved in a 6 % Yb-doped 10-mm-long CaF2 crystal at room temperature, outperforming any CW-diode-pumped scheme and paving the way towards very promising innovative lasers and amplifiers schemes merging the Yb-doped solid-state and fiber technologies.

Machinet, G.; Andriukaitis, G.; Sévillano, P.; Lhermite, J.; Descamps, D.; Pugžlys, A.; Baltuška, A.; Cormier, E.

2013-05-01

403

Abnormal upconversion luminescence from Yb3+ doped and Tb3+/Yb3+ codoped high silica glasses induced by intrinsic optical bistability  

NASA Astrophysics Data System (ADS)

Upconversion luminescence (UCL) properties from Yb3+ doped and Tb3+/Yb3+ codoped high silica glasses excited by a 980 nm laser diode are investigated. The ln-ln plots of the UCL intensity versus laser power show abnormal relations: the slopes are larger than those reported in other papers. When tuning the laser power up and down successively, intrinsic optical bistability of Yb3+ ions is observed at room temperature in the visible and infrared range without external cavity. And this nonlinear effect induces the abnormal UCL phenomena.

Zhang, Q.; Chen, G.; Xu, Y.; Liu, X.; Qian, B.; Dong, G.; Zhou, Q.; Qiu, J.; Chen, D.

2010-02-01

404

Synthesis of YbyCo4Sb12\\/Yb2O3 composites and their thermoelectric properties  

Microsoft Academic Search

Composites containing Yb-filled CoSb3 and well-distributed Yb2O3 particles are synthesized by in situ reaction method. The structural, chemical, and transport properties of the composites are studied. Some Yb2O3 particles with microsize locate at the grain boundaries of matrix and others distribute within YbyCo4Sb12 grains as nanoscale inclusions. The combination of the ``rattling'' of Yb ions inside the voids of CoSb3

X. Y. Zhao; X. Shi; L. D. Chen; W. Q. Zhang; S. Q. Bai; Y. Z. Pei; X. Y. Li; T. Goto

2006-01-01

405

Laser properties of Yb(sup 3+)-doped Sr(sub 5)(PO(sub 4))(sub 3)F crystals.  

National Technical Information Service (NTIS)

Yb(sup 3+) based lasers have received substantial attention over the past several years. Yb-based materials, which typically lase around 1 (mu)m, are aided by the simple electronic structure of Yb(sub 3+) in that it has only two accessible electronic stat...

C. D. Marshall S. A. Payne L. K. Smith K. I. Schaffers R. Beach

1994-01-01

406

Isotope shift and hyperfine structure measurements for 155Yb by laser ion source technique  

NASA Astrophysics Data System (ADS)

The change in the mean square charge radius and electromagnetic moments of the neutron deficient 155Yb isotope have been determined using resonance ionization spectroscopy in a laser ion source. The data point to an absence of a marked deformation change for Yb isotopes with N=84-86.

Barzakh, A. E.; Chubukov, I. Y.; Fedorov, D. V.; Moroz, F. V.; Panteleev, V. N.; Seliverstov, M. D.; Volkov, Y. M.

1998-01-01

407

Low spin states in 162 Yb and the X(5) critical point symmetry  

Microsoft Academic Search

Excited, nonyrast states in 162 Yb were populated through beta+ \\/? decay and studied through off-beam, beta -delayed gamma -ray spectroscopy at the Yale moving tape collector. New coincidence data provided evidence for a substantial revision of the previous level scheme and the elimination of a previously reported first excited 0+ state. The revised level scheme of 162 Yb is

E. A. McCutchan; N. V. Zamfir; M. A. Caprio; R. F. Casten; H. Amro; C. W. Beausang; D. S. Brenner; A. A. Hecht; C. Hutter; S. D. Langdown; D. A. Meyer; P. H. Regan; J. J. Ressler; A. D. Yamamoto

2004-01-01

408

Feasibility study for production of 175Yb: a promising therapeutic radionuclide.  

PubMed

Owing to its favourable decay characteristics 175Yb (T1/2 = 4.2 d, E beta(max) = 480 keV) can be regarded as a potential radionuclide for therapeutic applications. Production of 175Yb using (174Yb(n, gamma)175Yb) reaction by thermal neutron bombardment on natural ytterbium target is described. The activity of 175Yb produced as well as its radionuclidic purity under different irradiation conditions were determined by gamma-ray spectrometry using an HPGe 4 K MCA system and compared with theoretically calculated values. The radiochemical purity after chemical processing was determined by paper chromatography as well as paper electrophoresis techniques. It is found that 31 Ci/g (1145 GBq/g) of 175Yb can be produced with > 95% radionuclidic purity (with approximately 3% of 169Yb and approximately 2% of 177Lu) by irradiating natural Yb2O3 target at a thermal neutron flux of 3 x 10(13) n/cm2/s for a period of 5 d. PMID:12201133

Chakraborty, Sudipta; Unni, P R; Venkatesh, Meera; Pillai, M R A

2002-09-01

409

Hyperfine structure of Gamma6 electronic level in cubic Yb compound from Mössbauer spectroscopy  

Microsoft Academic Search

The hyperfine structure of the Gamma6 electronic level in the cubic compound Cs2NaYbCl6 has been observed from the Mössbauer studies of 170Yb. The effective hyperfine coupling constant is found to be -10.9+\\/-0.1 mm\\/sec.

G. K. Shenoy; R. Poinsot; L. Asch; J. M. Friedt; B. D. Dunlap

1974-01-01

410

Binding energies of Eu2+ and Eu3+ ions in ?-Ca2SiO4 doped with europium  

NASA Astrophysics Data System (ADS)

?-Ca2SiO4 doped with Eu2+and Eu3+was synthesized by solid state reaction. Europium replaces Ca2+ ions either as Eu2+ or Eu3+, both occupying two not equivalent sites; seven fold and eight fold coordinated by O2-. ?-Ca2SiO4:Eu2+, ?-Ca2SiO4:Eu3+ and ?-Ca2SiO4:Eu2+, Eu3+ samples were investigated by structural and spectroscopic methods. Specifically it has been shown that luminescence spectra of the ?-Ca2SiO4:Eu2+, Eu3+ system were a superposition of the Eu2+ and Eu3+ emission and were independent of temperature from 18 K to ambient. To explain this effect the short distance compensation of the Eu3+ replacing Ca2+ in the ?-Ca2SiO4 is discussed. It is argued that such compensation has to causes the conduction and valence bands bend. The existence of stable Eu2+ and Eu3+ replacing Ca2+ ion in lattice is discussed by consideration of the energies of the ground states of the Eu2+ and Eu3+, the Fermi energy and the energy necessary for creation of compensation defect.

Baran, Anna; Barzowska, Justyna; Grinberg, Marek; Mahlik, Sebastian; Szczodrowski, Karol; Zorenko, Yuriy

2013-10-01

411

Stimulated Raman adiabatic passage in Tm{sup 3+}:YAG  

SciTech Connect

We report on the experimental demonstration of stimulated Raman adiabatic passage in a Tm{sup 3+}:YAG crystal. Tm{sup 3+}:YAG is a promising material for use in quantum information processing applications, but as yet there are few experimental investigations of coherent Raman processes in this material. We investigate the effect of inhomogeneous broadening and Rabi frequency on the transfer efficiency and the width of the two-photon spectrum. Simulations of the complete Tm{sup 3+}:YAG system are presented along with the corresponding experimental results.

Alexander, A. L.; Lauro, R.; Louchet, A.; Chaneliere, T.; Le Goueet, J. L. [Laboratoire Aime Cotton, CNRS-UPR 3321, University Paris-Sud, Bat. 505, 91405 Orsay Cedex (France)

2008-10-01

412

[Studies on the properties of energy upconversion of the rare earth ErYb and HoYb in the oxyfluoride glass].  

PubMed

Er and Yb, Ho and Yb codoped in the oxyfluoride were burnt on in the specific temperature, and got two kinds of samples. Using 930 nm as an exciting light, the emitting fluorescent spectra of two kinds of the samples were measured, and observed the red band and green band fluorescent spectra, respectively. According to the detected absorption spectra of Er2O3, Ho2O3, Yb2O3 and the rule of energy jump, the mechanism and the properties of the energy upconversion of two kinds of the samples were explained. As can be seen, energy upconversion properties were determined mainly by the absorbtion spectra of Er2O3, Yb2O3. Energy upconversion efficiency were determined by excitative photons. PMID:12958886

Yuan, F C; Yang, X L; Liu, Z W

2001-12-01

413

Clock-transition spectrum of 171Yb atoms in a one-dimensional optical lattice  

NASA Astrophysics Data System (ADS)

An optical atomic clock with 171Yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6±3 ?K, which is close to the Doppler limit. Then, the cold 171Yb atoms are loaded into a one-dimensional optical lattice with a wavelength of 759 nm in the Lamb—Dicke regime. Furthermore, these cold 171Yb atoms are excited from the ground-state 1S0 to the excited-state 3P0 by a clock laser with a wavelength of 578 nm. Finally, the 1S0-3P0 clock-transition spectrum of these 171Yb atoms is obtained by measuring the dependence of the population of the ground-state 1S0 upon the clock-laser detuning.

Chen, Ning; Zhou, Min; Chen, Hai-Qin; Fang, Su; Huang, Liang-Yu; Zhang, Xiao-Hang; Gao, Qi; Jiang, Yan-Yi; Bi, Zhi-Yi; Ma, Long-Sheng; Xu, Xin-Ye

2013-09-01

414

Enhanced broadband near-infrared luminescence and optical amplification in Yb-Bi codoped phosphate glasses  

NASA Astrophysics Data System (ADS)

Yb-Bi codoped phosphate glass was prepared and its properties were compared with Bi-doped phosphate glass. The broadband infrared luminescence intensity from Yb-Bi codoped glass was ~32 times stronger than that of Bi-doped glass. The single-pass optical amplification was measured on a traditional two-wave mixing configuration. No optical amplification was observed in Bi-doped glass, while apparent broadband optical amplification between 1272 and 1336 nm was observed from Yb-Bi codoped glass with 980 nm laser diode excitation. The highest gain coefficient at 1272 nm of Yb-Bi codoped glass reached to 2.62 cm-1. Yb-Bi codoped phosphate glass is a promising material for broadband optical amplification.

Ruan, Jian; Wu, E.; Zeng, Heping; Zhou, Shifeng; Lakshminarayana, G.; Qiu, Jianrong

2008-03-01

415

Primary gamma transitions in 173,174Yb in neutron capture at isolated resonances  

NASA Astrophysics Data System (ADS)

Gamma transitions in 174Yb were investigated in radiative neutron capture at 23 isolated and additional 7 partially resolved summed resonances of 173Yb. The time-of-flight technique was used on an enriched target at the IBR-30 reactor at JINR Dubna. A total of 77 primary gamma transitions are reported populating levels in 174Yb up to 2.8 MeV in the spin parity range 1,2,3,4. Spin and parity assignments of neutron resonances and of populated levels are proposed. In addition to these results, seven primary gamma transitions in 173Yb were also observed from neutron capture at three isolated resonances of 172Yb.

Telezhnikov, S. A.; Granja, C.; Hiep, H. T.; Honzátko, J.; Králík, M.; Montero-Cabrera, M.-E.; Pospíšil, S.

2005-12-01

416

Spectroscopic properties of Yb3+ ions in La2(WO4)3 crystal  

NASA Astrophysics Data System (ADS)

Yb3+-doped La2(WO4)3 single crystals were grown by the Czochralski technique. Absorption and fluorescence spectra of the crystal were recorded at the room temperature. The stimulated emission cross-sections of Yb3+ ions were calculated using the reciprocity method and Fuchtbauer Ladenburg formula, respectively. The fluorescence decay curves of 2F5/2 manifold of Yb3+ ions were recorded at room temperature for both crystal and powder samples. The effect of radiation trapping on the spectroscopic properties is discussed. Comparison with other Yb3+-doped laser crystals is made. The results show that Yb3+:La2(WO4)3 crystal is a promising laser material.

Chen, Yujin; Lin, Xiuqin; Lin, Yanfu; Luo, Zundu; Huang, Yidong

2004-11-01

417

Laser properties of Yb(3+)-doped Sr5(PO4)3F crystals  

NASA Astrophysics Data System (ADS)

Yb(3+) based lasers have received substantial attention over the past several years. Yb-based materials, which typically lase around 1 micron, are aided by the simple electronic structure of Yb(3+) in that it has only two accessible electronic states eliminating the detrimental impact of upconversion or excited state absorption. In addition, the inherently small quantum defect of approximately 10-15% has led to relatively large intrinsic laser slope efficiencies. The pumping and extraction dynamics of Yb:Sr5(PO4)3F crystals will be discussed. A diode array and a free running Cr:LiSAF laser are utilized as pump sources for both Yb-oscillators and amplifiers.

Marshall, C. D.; Payne, S. A.; Smith, L. K.; Schaffers, K. I.; Beach, R.; Emanuel, M.; Powell, H. T.; Krupke, W. F.; Chai, B. H. T.

1994-06-01

418

Incorporation and Luminescence of Yb(3+) in CdSe Nanocrystals.  

PubMed

Doping quantum dots (QDs) with lanthanide ions is promising to combine the efficient sharp line emission of lanthanides with the strong and size-tunable absorption of QDs. Incorporating lanthanide ions in II-VI QDs remains challenging, however, here we report successful coupling of CdSe QDs with the lanthanide ion Yb(3+). Our spectroscopic results demonstrate that Yb(3+) ions are first adsorbed on the CdSe surface and subsequently incorporated in the nanocrystalline semiconductor particles by growing a Se shell. Evidence for incorporation is provided by the fine structure of the CdSe QDs absorption in the excitation spectrum of the Yb(3+) emission at 1000 nm and the long lifetime of the Yb(3+) emission after shell overgrowth. Sensitized Yb(3+) infrared emission may find application in optical amplifiers, solar concentrators, and bioimaging. The method described is a promising strategy for incorporating lanthanide ions in other II-VI QDs. PMID:24000937

Martín-Rodríguez, Rosa; Geitenbeek, Robin; Meijerink, Andries

2013-09-05

419

EU Policy in the South Caucasus A view from Azerbaijan  

Microsoft Academic Search

Since the accession of Romania and Bulgaria to the EU in January 2007, the South Caucasus has become a region of direct concern to the EU's strategy in its wider neighbourhood. This study examines the trends affecting EU policies in the South Caucasus, with a specific focus on EU-Azerbaijan relations. It argues that in the three main areas in which

Elkhan Nuriyev

420

Russia and the EU: The Clash of New Neighbourhoods?  

Microsoft Academic Search

The enlargement of the EU eastwards and the development of the European Neighbourhood Policy has meant the EU developing explicit interests in the former Soviet states. In this there is the potential for tension with Russia in a shared neighbourhood. In particular, with the accession of Bulgaria and Romania to the EU in 2007 the EU has become a Black

PAUL FLENLEY

2008-01-01

421

The EU as an Agent for Democracy: Images of the EU in the Pacific Media ‘Mirror’  

Microsoft Academic Search

The Pacific is a major recipient of EU assistance under the Cotonou Agreement and target for EU development actions (including the reinforcement of democracy and human rights). Positioning its inquiry within the diffusion theory, this study focuses on one of the Union’s ‘normative’ profiles communicated externally, namely the EU’s international performance as a promoter of democracy,rule of law and human

Martin Holland; Natalia Chaban

2011-01-01

422

Paramagnetic hyperfine structure in 151Eu Mossbauer spectra of Eu2+ ions in borate glasses  

Microsoft Academic Search

Europium borate glasses containing 0.1-33 mol.% EuO have been prepared to study the 151Eu Mossbauer spectra. The results depend strongly on the concentration of Eu2+ ions in the glasses. In diluted systems, split patterns have been observed which originate from paramagnetic hyperfine interactions, as proved by the addition of Mn2+ ions to the glass. There is only a weak dependence

M. Winterer; E. Morsen; B. D. Mosel; W. Muller-Warmuth

1987-01-01

423

First-principles study of one-dimensional sandwich wires [(P)5TM]? (TM = Ti, V, Cr, Mn, Fe, Co)  

NASA Astrophysics Data System (ADS)

Since the discovery of ferrocene, many one-dimensional metallic sandwich molecular wires have been identified. However, most of the known systems are assembled from organic molecules. Suffering from many drawbacks has, however, hampered their widespread applications. With the goal of breaking this logjam, we provide a blueprint for the designing of a variety of novel sandwich molecular wires ([(P)5TM]?, TM = Ti, V, Cr, Mn, Fe, and Co) assembled from ferrocene-like inorganic molecules (P)5TM, offering evidence of the existence of inorganic molecular wires in this class. We present first-principles calculations to investigate systematically the electronic and magnetic properties of such novel inorganic sandwich molecular wires. Compared with the organic molecular wires, all the inorganic [(P)5TM]? wires are of large magnetic moment. Among them, we find that [(P)5V]?, [(P)5Cr]? and [(P)5Mn]? display ferromagnetic character, while for [(P)5Ti]?, [(P)5Fe]? and [(P)5Co]?, the magnetic coupling is antiferromagnetic. More remarkably, the TM atoms distributed in these wires show regular docking and lead to structures with ordered spin signals, which is a long-term dream of spintronics. We propose that the difference in magnetic coupling for the studied systems is related to the competition between two exchange interactions of TM atoms. Specifically, we propound that the general mechanism for the formation of stable 1D [(P)5TM]? involves the transfer of one electron from the TM atom to the P5 ligand forming ({P})_{5}^{-} and TM+ alternating structure.

Ma, Yandong; Dai, Ying; Li, Xinru; Li, Zhujie; Huang, Baibiao

2013-10-01

424

First-principles study of one-dimensional sandwich wires [(P)?TM]? (TM = Ti, V, Cr, Mn, Fe, Co).  

PubMed

Since the discovery of ferrocene, many one-dimensional metallic sandwich molecular wires have been identified. However, most of the known systems are assembled from organic molecules. Suffering from many drawbacks has, however, hampered their widespread applications. With the goal of breaking this logjam, we provide a blueprint for the designing of a variety of novel sandwich molecular wires ([(P)5TM]?, TM = Ti, V, Cr, Mn, Fe, and Co) assembled from ferrocene-like inorganic molecules (P)5TM, offering evidence of the existence of inorganic molecular wires in this class. We present first-principles calculations to investigate systematically the electronic and magnetic properties of such novel inorganic sandwich molecular wires. Compared with the organic molecular wires, all the inorganic [(P)5TM]? wires are of large magnetic moment. Among them, we find that [(P)5V]?, [(P)5Cr]? and [(P)5Mn]? display ferromagnetic character, while for [(P)5Ti]?, [(P)5Fe]? and [(P)5Co]?, the magnetic coupling is antiferromagnetic. More remarkably, the TM atoms distributed in these wires show regular docking and lead to structures with ordered spin signals, which is a long-term dream of spintronics. We propose that the difference in magnetic coupling for the studied systems is related to the competition between two exchange interactions of TM atoms. Specifically, we propound that the general mechanism for the formation of stable 1D [(P)5TM]? involves the transfer of one electron from the TM atom to the P5 ligand forming [Formula: see text] and TM(+) alternating structure. PMID:24002217

Ma, Yandong; Dai, Ying; Li, Xinru; Li, Zhujie; Huang, Baibiao

2013-09-04

425

Crystallization and photoluminescence properties of ?-RE2(WO4)3 (RE: Gd, Eu) in rare-earth tungsten borate glasses  

NASA Astrophysics Data System (ADS)

Glasses with the compositions of 22.5RE2O3-47.5WO3-30B2O3 (mol%) (RE: Gd, Eu) were prepared by a conventional melt quenching method, and ?-Gd2(WO4)3 and ?-Eu2(WO4)3 crystals were synthesized through their crystallization. The two types of WO4 tetrahedra present in ?-RE2(WO4)3 provide the Raman bands at 931-934 cm-1 for WIIO4 tetrahrdra with much distortions and at 946-950 cm-1 for WIO4 tetrahedra with a near regular symmetry. The crystallized samples containing ?-Eu2(WO4)3 exhibit strong red emissions under the excitation at 396 and 467 nm, although the base glass has no photoluminescence emission. ?-Gd2(WO4)3 and ?-Eu2(WO4)3 crystals were patterned on the glass surface by irradiations of a continuous wave Yb:YVO4 fiber laser (wavelength: 1080 nm).

Wang, Yong; Honma, Tsuyoshi; Komatsu, Takayuki

2013-03-01

426

Wavelengths, classifications, and ionization energies in the isoelectronic sequences from Yb II and Yb III through Bi XV and Bi XVI  

Microsoft Academic Search

Spectral observations are reported for transitions to the ground term and first excited term of the one-electron configurations in the 4f¹⁴5p⁶nl isoelectronic sequence from Yb II through Bi XV. Resonance lines are reported for the isoelectronic sequence Yb III through Bi XVI in which the ground state is 4f¹⁴5p⁶ ¹Sâ and the upper levels are the J = 1 levels

Victor Kaufman; Jack Sugar

1976-01-01

427

{beta}-decay study of {sup 150}Er, {sup 152}Yb, and {sup 156}Yb: Candidates for a monoenergetic neutrino beam facility  

SciTech Connect

The {beta} decays of {sup 150}Er, {sup 152}Yb, and {sup 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.; Algora, A.; Rubio, B.; Bernabeu, J.; Nacher, E.; Tain, J. L.; Gadea, A.; Agramunt, J.; Burkard, K.; Hueller, W.; Doering, J.; Kirchner, R.; Mukha, I.; Plettner, C.; Roeckl, E.; Grawe, H.; Collatz, R.; Hellstroem, M.; Cano-Ott, D.; Karny, M. [IFIC, CSIC-Universidad de Valencia, E-46071 Valencia (Spain); GSI, D-64291 Darmstadt (Germany); CIEMAT, E-28000, Madrid (Spain); Institute of Experimental Physics, University of Warsaw, PL-00-681 Warsaw (Poland); ORNL, Oak Ridge, Tennessee 37831 (United States); PNPI, 188300 Gatchina (Russian Federation); IKP, University of Cologne, D-50937 Cologne (Germany); INFN LNL, I-35020 Legnaro (Padova) (Italy); CFPT-IST, 1049-001 Lisbon (Portugal)

2011-09-15

428

Guide to EU Standards and Conformity Assessment.  

National Technical Information Service (NTIS)

This guide is an easy-to-use introductory reference for industry and government officials on the general principles and concepts behind the European Union's (EU) 'New Approach' laws and directives. It is designed to help business and government officials ...

H. Delaney R. van de Zande

2000-01-01

429

Quantum Criticality and Superconductivity in ?-YbAlB4  

NASA Astrophysics Data System (ADS)

Heavy fermion systems have provided a number of prototypical compounds to study unconventional superconductivity and non-Fermi-liquid (NFL) states. A long standing issue in the research of heavy fermion superconductivity in 4f intermetallics is the dramatically different behavior between the electron like Ce (4f^1) and hole like Yb (4f^13) compounds. While superconductivity has been found in a number of Ce based heavy fermion compounds, no superconductivity has been reported for the corresponding Yb systems. In this talk, I present our recent finding of the superconductivity in the new heavy fermion system ?-YbAlB4 [1-3]. The superconducting transition temperature is 80 mK, and above it, the system exhibits pronounced NFL behavior in the transport and thermodynamic properties [2,3]. Furthermore, the magnetic field dependence of the NFL behavior indicates that the system is a rare example of a pure metal that displays quantum criticality at ambient pressure and under zero magnetic field. Using our latest results, we discuss the detailed properties of superconductivity and quantum criticality. This is the work performed in collaboration with K. Kuga, Y. Matsumoto, T. Tomita, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, S. Yonezawa, Y. Maeno, E. Pearson, G. G. Lonzarich, L.Balicas, H. Lee, and Z. Fisk. [4pt] [1] Robin T. Macaluso, Satoru Nakatsuji, Kentaro Kuga, Evan Lyle Thomas, Yo Machida, Yoshiteru Maeno, Zachary Fisk, and Julia Y. Chan, Chem. Mater. 19 1918 (2007). [0pt] [2] S. Nakatsuji, K.Kuga, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, S. Yonezawa, Y. Maeno, E. Pearson, G. G. Lonzarich, L.Balicas, H. Lee, and Z. Fisk, Nature Phys 4, 603-607 (2008). [0pt] [3] K. Kuga, Y. Karaki, Y. Matsumoto, Y. Machida, and S. Nakatsuji, Phys. Rev. Lett. 101, 137004 (2008).

Nakatsuji, Satoru

2009-03-01

430

The reduction of Eu3+ to Eu2+ in BaMgAl10O17:Eu and the photoluminescence properties of BaMgAl10O17:Eu2+ phosphor  

NASA Astrophysics Data System (ADS)

The variations in emission intensities of AlO4-tetrahedron-containing compound BaMgAl10O17:Eu (BAM) phosphor prepared in different atmospheres is discussed in view of the structure of host compounds. A reduction phenomenon of Eu3+-->Eu2+ was observed by emission and excitation spectra measurement in BAM for the first time. This reduction was explained by a charge compensation mechanism and the photoluminescence properties were discussed. By comparison, it was found that Eu2+ ions occupy three different lattice sites by substitution for Ba2+ ions in BaMgAl10O17:Eu2+. BaMgAl10O17:Eu2+ phosphors exhibited more excellent thermal stability when Eu2+ ions occupied more Eu (1) sites, and gave a dominating contribution for the photoluminescence when Eu2+ ions occupied Eu (2) sites.

Liu, Bitao; Wang, Yuhua; Zhou, Jun; Zhang, Feng; Wang, Zhaofeng

2009-09-01

431

A Single EU Seat in the IMF?  

Microsoft Academic Search

AbstractThis article examines the rationale for consolidating EU Member States' position in the International Monetary Fund (IMF). Although a substantial amount of co-ordination already takes place, particularly on issues related to the euro area and the single monetary and exchange rate policy, co-operation between EU countries in the IMF remains a relatively new phenomenon and divergences still prevail. The current

Lorenzo Bini Smaghi

2004-01-01

432

Safety evaluation of cosmetics in the EU  

Microsoft Academic Search

Council Directive 76\\/768\\/EEC, its seven amendments and 30 adaptations to technical progress form the basis of the cosmetic EU legislation today.There are actually four key principles for safety in the cosmetic legislation.(i)The full responsibility for the safety of cosmetics for human health is placed on the manufacturer, first importer in the EU or marketer.(ii)The safety evaluation of finished products is

Marleen Pauwels; Vera Rogiers

2004-01-01

433

Antiferromagnetism in EuNiGe3  

NASA Astrophysics Data System (ADS)

The synthesis and crystallographic and physical properties of polycrystalline EuNiGe3 are reported. EuNiGe3 crystallizes in the noncentrosymmetric body-centered tetragonal BaNiSn3-type structure (space group I4mm), in agreement with previous reports, with the Eu atoms at the corners and body center of the unit cell. The physical property data consistently demonstrate that this is a metallic system in which Eu spins S=7/2 order antiferromagnetically at a temperature TN=13.6 K. Magnetic susceptibility ? data for T>TN indicate that the Eu atoms have spin 7/2 with g=2, that the Ni atoms are nonmagnetic, and that the dominant interactions between the Eu spins are ferromagnetic. Thus we propose that EuNiGe3 has a collinear A-type antiferromagnetic structure, with the Eu ordered moments in the ab plane aligned ferromagnetically and with the moments in adjacent planes along the c axis aligned antiferromagnetically. A fit of ?(T?TN) by our molecular field theory is consistent with a collinear magnetic structure. Electrical resistivity ? data from TN to 350 K are fitted by the Bloch-Grüneisen model for electron-phonon scattering, yielding a Debye temperature of 265(2) K. A strong decrease in ? occurs below TN due to loss of spin-disorder scattering. Heat capacity data at 25K?T?300 K are fitted by the Debye model, yielding the same Debye temperature 268(2) K as found from ?(T). The extracted magnetic heat capacity is consistent with S=7/2 and shows that significant short-range dynamical spin correlations occur above TN. The magnetic entropy at TN=13.6 K is 83% of the expected asymptotic high-T value, with the remainder recovered by 30 K.

Goetsch, R. J.; Anand, V. K.; Johnston, D. C.

2013-02-01

434

Comparing Poverty Indicators in an Enlarged EU  

Microsoft Academic Search

In this paper, using the EU-SILC 2006 data-set, we seek to explore the extent to which a consideration of welfare regime and socio-economic differences in poverty levels and patterns and variation in the consequences of poverty for economic stress can assist us in making informed choices between alternative poverty indicators. Poverty in the EU is normally defined in terms of

Christopher T. Whelan; Bertrand Maitre

2008-01-01

435

In Situ Growth of a Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications  

NASA Astrophysics Data System (ADS)

The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000°C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit ( zT) over that of Si-Ge at 1000°C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000°C (˜3 × 10-3 g/cm2 h) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.

Nesbitt, James A.; Opila, Elizabeth J.; Nathal, Michael V.

2012-06-01