992 resultados para Yb^3
Resumo:
(2-)(H[DEHP])()()()(),H[DEHP]Sc~(3+)>Fe~(3+)>Lu~(3+)>Yb~(3+)>Er~(3+)>Y~(3+)>Ho~(3+)Sc()Fe()Y()Ln()()Fe()(),HEH[EHP]IRNMR,H[DEHP]Sc()Y()Ln(),
Resumo:
~1H~(13)C NMR(-,GA)Yb-Dy~(3+)Ho~(3+)Er~(3+)Tr~(3+)Yb~(3+)GA~(13)C,Reuben,Cl-C_2-N-C_3,C_2-N-C_3-C_4C_5-C_2-N-C_34
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~(13)CDy~(3+)Ho~(3+)Er~(3+)Tm~(3+)Yb~(3+)~(13)C~1H,1
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(La~(3+)Ho~(3+)Yb~(3+)-~1H~(13)CHoYb-,,-
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2-(2-)(HEHEHP,HL)1--3--4--5(PMBP,HA)(H_2SO_4,HCl HNO_3)()Nd~(3+),Yb~(3+),Lu~(3+),HEHEHP-PMBPHNO_3(),,Nd(HL_2)A_2,Yb(HL_2)A,Lu(HL_2)_2A,,,IRNMR
Resumo:
11(La~(3+)Pr~(3+)Nd~(3+)Eu~(3+)Tb~(3+)Dy~(3+)Ho~(3+)Er~(3+)Tm~(3+)Yb~(3+)Lu~(3+)~(13)C~(1)H,,,Ln~(3+)-O2.1
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Ln~(3+)Ce~(3+),Eu~(3+)Yb~(3+)CeP_5O_(14)Ce~(3+),Ce~(3+)302nm,Ce~(3+),Yb~(3+),Yb~(3+),Ce~(3+)
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A new preparation route towards rare-earth (RE) doped polycrystalline lead lanthanum zirconate titanate (PLZT) ceramics (RE = Y(3+), Nd(3+), Yb(3+)), based on the use of doped lanthanum oxide or zirconia, is reported. Structural characterization by X-ray powder diffraction reveals that secondary phase formation can be substantially diminished in comparison to conventional preparation methods. The distribution of the rare-earth dopants was investigated as a function of concentration by static (207)Pb spin echo NMR spectra, using Fourier Transformation of Carr-Purcell-Meiboom-Gill spin echo trains. For the Nd- and Yb-doped materials, the interaction of the (207)Pb nuclei with the unpaired electron spin density results in significant broadening and shifting of the NMR signal, whereas these effects are absent in the diamagnetic Y(3+) doped materials. Based on different concentration dependences of the NMR lineshape parameters, we conclude that the structural role of the Nd(3+) dopants differs significantly from that of Yb(3+). While the Nd(3+) ions appear to be statistically distributed in the PLZT lattice, incorporation of Yb(3+) into PLZT appears to be limited by the appearance of doped cubic zirconia as a secondary phase. (C) 2009 Elsevier Masson SAS. All rights reserved.
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The crystallization of laser glasses in the system (B(2)O(3))(0.6){(Al(2)O(3))(0.4-y)(Y(2)O(3))(y)} (0.1 <= y <= 0.25) doped with different levels of ytterbium oxide has been investigated by X-ray powder diffraction, differential thermal analysis, and various solid-state NMR techniques. The homogeneous glasses undergo major phase segregation processes resulting in crystalline YBO(3), crystalline YAI(3)(BO(3))(4), and residual glassy B(2)O(3) as the major products. This process can be analyzed in a quantitative fashion by solid-state (11)B, (27)Al, and (89)Y NMR spectroscopies as well as (11)B{(27)Al} rotational echo double resonance (REDOR) experiments. The Yb dopants end up in both of the crystalline components, producing increased line widths of the corresponding (11)B, (27)Al, and (89)Y NMR resonances that depend linearly on the Yb/Y substitution ratio. A preliminary analysis of the composition dependence suggests that the Yb(3+) dopant is not perfectly equipartitioned between both crystalline phases, suggesting a moderate preference of Yb to substitute in the crystalline YBO(3) component.
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Cooperative energy transfer upconversion luminescence is investigated in Tb(3+)/Yb(3+)-codoped PbGeO(3)-PbF(2)-CdF(2) glass-ceramic and its precursor glass under resonant and off resonance infrared excitation. Bright UV-visible emission signals around 384, 415, 438 nm, and 473-490, 545, 587, and 623 nm are identified as due to the (5)D(3)((5)G(6))->(7)F(1) (J=6,5,4) and (5)D(4)->(7)F(1) (J=6,5,4,3) transitions, respectively, and readily observed. The results indicate that cooperative energy transfer between ytterbium and terbium. ions followed by excited state absorption are the dominant upconversion excitation mechanisms involved. Comparison of the upconversion process in a glass-ceramic sample and its glassy precursor revealed that the former present much higher upconversion efficiency. The dependence of the upconversion emission upon pump power, temperature, and doping content is also examined.
Resumo:
Cooperative energy-transfer upconversion luminescence in Tb 3+/Yb 3+-codoped PbGeO 3-PbF 2-CdF 2 vitroceramic and its precursor glass under resonant and off-resonance infrared excitation, is investigated. Bright UV-visible emission signals around 384, 415, 438 nm, and 473-490, 545, 587, and 623 nm, identified as due to the 5D 3( 5G 6 7F J(J=6,5,4) and 5D 4 7F J(J=6,5,4,3) transitions, respectively, were readily observed. The results indicate that cooperative energy-transfer between ytterbium and terbium ions followed by excited-state absorption are the dominant upconversion excitation mechanisms herein involved. The comparison of the upconversion process in a vitroceramic sample and its glassy precursor revealed that the former present much higher upconversion efficiency. The dependence of the upconversion emission upon pump power, temperature, and doping content is also examined.
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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 Pr 3+:3P0 3H4 (482 nm), Pr3+:1D2 3H6 (800 nm), Yb3+:2F5/2 2F 7/2 (1044 nm) transitions and the photoluminescence excitation spectra were measured in Pr3+ samples and in Pr3+-Yb 3+ 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 (Pr 3+: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; Yb 3+:2F7/2 2F5/2). 2013 Elsevier B.V. All rights reserved.
Resumo:
O presente trabalho tem como objetivo estudar a produo e caracterizao de filmes finos do tipo GeO2-Bi2O3 (BGO) produzidos por sputtering-RF com e sem nanopartculas (NPs) semicondutoras, dopados e codopados com ons de Er3+ ou Er3+/Yb3+ para a produo de amplificadores pticos. A produo de guias de onda do tipo pedestal baseados nos filmes BGO foi realizada a partir de litografia ptica seguida por processo de corroso por plasma e deposio fsica a vapor. A incorporao dos ons de terras-raras (TRs) foi verificada a partir dos espectros de emisso. Anlises de espectroscopia e microscopia foram indispensveis para otimizar os parmetros dos processos para a construo dos guias de onda. Foi observado aumento significativo da luminescncia do Er3+ (regio do visvel e do infravermelho), em filmes finos codopados com Er3+/Yb3+ na presena de nanopartculas de Si. As perdas por propagao mnimas observadas foram de ~1,75 dB/cm para os guias pedestal em 1068 nm. Para os guias dopados com Er3+ foi observado aumento significativo do ganho na presena de NPs de silcio (1,8 dB/cm). O ganho ptico nos guias de onda amplificadores codopados com Er3+/Yb3+ e dopados com Er3+ com e sem NPs de silcio tambm foi medido. Ganho de ~8dB/cm em 1542 nm, sob excitao em 980 nm, foi observado para os guias pedestal codopados com Er3+/Yb3+ (Er = 4,64.1019 tomos/cm3, Yb = 3,60.1020 tomos/cm3) com largura de 80 m; para os guias codopados com concentrao superior de Er3+/Yb3+ (Er = 1,34.1021 tomos/cm3, Yb = 3,90.1021 tomos/cm3) e com NPs de Si, foi observado aumento do ganho ptico de 50% para guia com largura de 100 m. Os resultados apresentados demonstram que guias de onda baseados em germanatos, com ou sem NPs semicondutoras, so promissores para aplicaes em dispositivos fotnicos.
Resumo:
We apply our technique of using a Rb-stabilized ring-cavity resonator to measure the frequencies of various spectral components in the 555.8-nm 1S0-->3P1 line of Yb. We determine the isotope shifts with 60 kHz precision, which is an order-of-magnitude improvement over the best previous measurement on this line. There are two overlapping transitions, 171Yb(1/2-->3/2) and 173Yb(5/2-->3/2), which we resolve by applying a magnetic field. We thus obtain the hyperfine constants in the 3P1 state of the odd isotopes with a significantly improved precision. Knowledge of isotope shifts and hyperfine structure should prove useful for high-precision calculations in Yb necessary to interpret ongoing experiments testing parity and time-reversal symmetry violation in the laws of physics.
