103 resultados para PR3
Resumo:
Based on the rate equations describing the operation of the Er3+, Pr3+ -codoped ZBLAN fiber lasers with different pump configurations, theoretical calculations that relate to the population characteristics and optimization of CW operation of high power Er3+, Pr3+ :ZBLAN double-clad fiber lasers are presented. Using the measured ET (energy-transfer), ETU (energy-transfer-upconversion) and CR (cross-relaxation) parameters relevant to Er3+, Pr3+ -codoped ZBLAN, a good agreement between the theoretical results from the model and recently reported experimental measurements is obtained. The effects on the slope efficiency of a number of laser parameters including fiber length, reflectance of the output mirror and pumping configuration are quantitatively analyzed and used for the design and optimization of high power Er3+, Pr3+ -codoped ZBLAN fiber lasers.
Resumo:
Based on the rate equations describing the operation of the Er3+, Pr3+ -codoped ZBLAN fiber lasers with different pump configurations, theoretical calculations that relate to the population characteristics and optimization of CW operation of high power Er3+, Pr3+ :ZBLAN double-clad fiber lasers are presented. Using the measured ET (energy-transfer), ETU (energy-transfer-upconversion) and CR (cross-relaxation) parameters relevant to Er3+, Pr3+ -codoped ZBLAN, a good agreement between the theoretical results from the model and recently reported experimental measurements is obtained. The effects on the slope efficiency of a number of laser parameters including fiber length, reflectance of the output mirror and pumping configuration are quantitatively analyzed and used for the design and optimization of high power Er3+, Pr3+ -codoped ZBLAN fiber lasers.
Resumo:
The reaction of [M2Cl2(mu-Cl)(2)(PR3)(2)] (M=Pd or Pt; PR3=PEt3, PBu3, PMe2Ph, PMePh2) with lithium amidinate or sodium triazenide gave binuclear complexes containing amidinato- or triazenido-bridges, [M2Cl2(mu-ArNENAr)(2)(PR3)(2)] (E=CH, CMe or N). These complexes were characterized by elemental analysis and NMR (H-1, P-31 or Pt-195) data. The structures of two complexes, [(PdCl2)-Cl-2(mu-PhNC(Me)NPh)(2)(PMe2Ph)(2)] (10) and [Pt2Cl2(mu-PhNNNPh)(2)(PEt3)(2)] (11) were established by single crystal X-ray structural analyses. The Pt-195 NMR data Show coupling between two metal centers in the cis triazenido-bridged complex. The corresponding amidinate bridged complex does not show coupling. The role of the bridging ligand in mediating interaction between the metal centers is probed through Extended Huckel Theory (EHT) calculations. It is suggested that M-M interactions are primarily affected by the bridging ligands
Resumo:
We present the x-ray absorption data at the oxygen K-edge using total yield technique for Gd1xPrxba2Cu3O7 (x= 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0). The data clearly to oxygen that the holes doped in the GdBa2Cu3O7 due to oxygen composition are not removed by Pr doping even for the x = 1.0 sample, suggesting that Pr is predominantly in the formally trivalent state. However, the data also clearly indicate the evidence of hybridization effects between the Pr3+ and the adjacent CuO2 layers. This is suggested to be responsible for the progressive suppression of Tc and the metallicity with Pr doping in these systems.
Resumo:
The reaction of fac-[Mo(CO)3(MeCN)3] with the unsymmetrical diphosphazane Ph2PN(iPr)P(Ph)(DMP) (L) gives the complex fac-[Mo(CO)3(MeCN)(L)] (2) in almost quantitative yield. The structure of the complex has been determined by an X-ray diffraction study. The compound reacts with PR3 (where R = Ph, OPh) to give fac-[Mo(CO)3(PR3)(L)] (3a, 4a), which undergoes an intramolecular isomerization to afford mer-[Mo(CO)3(PR3)(L)] (3b, 4b). Synthesis of cis-[Mo(CO)4(L)] (1) and fac-[MO(CO)3L] (2a) and their spectroscopic data are also reported.
Resumo:
Thin films of cobalt oxide have been deposited on various substrates, such as glass, Si(100), SrTiO3(100), and LaAlO3(100), by low pressure metalorganic chemical vapor deposition (MOCVD) using cobalt(IL), acetylacetonate as the precursor. Films obtained in the temperature range 400-600 degreesC were uniform and highly crystalline having Co3O4 phase as revealed by x-ray diffraction. Under similar conditions of growth, highly oriented thin films of cobalt oxide grow on SrTiO3(100) and LaAlO3(100). The microstructure and the surface morphology of cobalt oxide films on glass, Si(100) and single crystalline substrates, SrTiO3(100) and LaAlO3(100) were studied by scanning electron microscopy. Optical properties of the films were studied by uv-visible-near IR spectrophotometry.
Resumo:
Spontaneous halide ejection from a three-coordinate Lewis acid has been shown to offer a remarkable new route to cationic metal complexes featuring a linear, multiply bonded boron-donor Ligand. The exploitation of electron-rich [CpM(PR3)(2)] fragments within boryl systems of the type LnMB(hal)NR2 leads to the spontaneous formation in polar solvents of chemically robust borylene complexes, [LnM(BNR2)](+), with exceptionally low electrophilicity and short M-B bonds. This is reflected by M-B distances (ca. 1.80 angstrom for FeB systems) which are more akin to alkyl-/aryl-substituted borylene complexes and, perhaps most strikingly, by the very low exothermicity associated with the binding of pyridine to the two-coordinate boron center (Delta H = -7.4 kcal mol(-1), cf. -40.7 kcal mol(-1) for BCl3). Despite the strong pi electron release from the metal fragment implied by this suppressed reactivity and by such short M-B bonds, the barrier to rotation about the Fe=B bond in the unsymmetrical variant [CpFe(dmpe)(BN{C6H4OMe-4}Me)](+) is found to be very small (ca. 2.9 kcal mol(-1)). This apparent contradiction is rationalized by the orthogonal orientations of the HOMO and HOMO-2 orbitals of the [CpML2](+) fragment, which mean that the M-B pi interaction does not fall to zero even in the highest energy conformation.
Resumo:
Near-infrared to ultraviolet upconversion luminescence was observed in the Pr3+ :Y2SiO5 crystal with 120 fs, 800 mn infrared laser irradiation. The observed emissions at around 270 nm and 305 nm could be assigned to 5d -> 4f transitions of Pr3+ ions. The relationship between the upconversion luminescence intensity and the pump power of the femtosecond laser reveals that the UV emission belongs to simultaneous three-photon absorption induced upconversion luminescence. (c) 2007 Elsevier B.V. All rights reserved.
Resumo:
We report on cooperative downconversion in Yb3+-RE3+ (RE = Tm or Pr) codoped lanthanum borogermanate glasses (LBG), which are capable of splitting a visible photon absorbed by Tm3+ or Pr3+ ions into two near-infrared photons. The results indicate that Pr3+-Yb3+ is a more efficient ion couple than Tm3+-Yb3+ in terms of cooperative downconversion. We have obtained a highest quantum yield of 165% and 138% for Pr3+-Yb3+ and Tm3+-Yb3+ codoped LBG glasses under 468 nm excitation, respectively. However, ultraviolet light excitation to the charge transfer band of Yb3+ does not result in quantum splitting as rapid relaxation from the charge transfer band to 4f(13) levels of Yb3+ dominates. (C) 2008 Optical Society of America
Resumo:
Field Emission Displays, FEDFEDFED (FED)(FED)-(FED) [(LaGaO3: Re3+ (Re = Eu, Tb, Dy, Tm, Sm)][(CaIn2O4: Re3+ (Re = Eu, Pr, Tb, Dy,)][(SrIn2O4: Re3+ (Re = Pr, Tb, Dy)][Lu3Ga5O12:Re3+ (Re = Eu, TbPr)]Pr, Sm, Eu, Tb, Dy, TmSr2CeO4SiO2CaTiO3:Pr3+, Y3Al5O12:Ce3+/Tb3+/Ga2O3:Dy3+XRDFTIRSEMTEM(PL)(CL) (LaGaO3)(Eu3+, Tb3+, Dy3+, Tm3+, Sm3+)(Eu3+, Tb3+, Dy3+, Tm3+, Sm3+)LaGaO3: Eu3+LaGaO3: Dy3+LaGaO3: Tm3+LaGaO3: Sm3+LaGaO3: Sm3+,Tb3+LaGaO3: Tb3+Tb3+LaGaO3: Tb3+LaGaO3: Tm3+FED(Y2SiO5: Ce3+NP-1047)LaGaO3: Sm3+((Zn,Cd)S: AgNP-1020)(LaGaO3: Sm3+,Tb3+), [(LaGaO3: Re3+ (Re = Eu, Tb, Dy, Tm, Sm )] Sr/CaIn2O4Sr/CaIn2O4Pr3+/Tb3+/Dy3+Sr/CaIn2O4Pr3+/ Tb3+/Dy3+Pr3+/Tb3+/Dy3+Sr/CaIn2O4: Pr3+/Tb3+/Dy3+(CL)(PL)CL CaIn2O4:Eu3+CaIn2O4:Eu3+Eu3+ Lu3Ga5O12:Re3+ (Re = Eu, TbPr)UVLu3Ga5O12: Eu3+, Lu3Ga5O12: Pr3+Eu3+, Pr3+Lu3Ga5O12:Tb3+Tb3+ Sr2CeO4UV(Ce4+-O2-) SiO2@CaTiO3:Pr3+SiO2@Y3Al5O12: Ce3+/Tb3+, FESEMTEMSiO2UVSiO2@CaTiO3:Pr3+Pr3+ 1D23H4 (612 nm)SiO2@Y3Al5O12:Ce3+SiO2@Y3Al5O12:Tb3+ Ce3+5d-4fTb3+5D4-7FJ (J = 6, 5, 4, 3)PLCL Ga2O3:Dy3+-Ga2O3:Dy3+--Ga2O3Dy3+--Ga2O3:Dy3+
Resumo:
MAIF5MCaSrBaLIMAIFaMCaSrCaAIFSrAIFBaAICaAIF6LrAISrAlF5LiSrAlF6llCoAIF6BaAlF5LiCaAlF6KMgF3:EuKMgFa:EU6P7/28S7/2420nml6P7/2-8S7/2Eu3+GdEuKMgFaBaLiF3BaY2F8Gd2+Eu2+Gd3+Eu2+Gd3+Eu2+Pr+ KMgF2LiYF4BaY2F8KMgFa:Pr3+352nmPr3+KMg1-xCaxF3Pr3+Ca2MgSi2O2EuEu3+Eu2+Ca2Eu8Si6O26X-ray
Resumo:
-Ce0.87Sm0.13-xPrxO2-(x=0.00,0.01,0.02),X,,PrCe0.87Sm0.13O2-.,Pr3+,,,.
Resumo:
Lu3Ga5O12:Eu3+, Lu3Ga5O12:Tb3+, and Lu3Ga5O12:Pr3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence, and cathodoluminescence spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the sample begins to crystallize at 800 degrees C and fully crystallined pure Lu3Ga5O12 phase can be obtained at 1000 degrees C. The FESEM image indicates that the phosphor sample is composed of aggregated rice grainlike particles with sizes around 80-120 nm.
Resumo:
LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the pure LaInO3 phase can also be obtained at 700 degrees C. FE-SEM images indicate that the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors are composed of aggregated spherical particles with sizes around 80-120 nm. Under the excitation of ultraviolet light and low voltage electron beams (1-5 kV), the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors show the characteristic emissions of Sm3+ ((4)G(5/2)-H-6(5/2,7/2,9/2) transitions, yellow), Pr3+ (P-3(0)-H-3(4), P-3(1)-H-3(5), D-1(2)-H-3(4) and P-3(0)-F-3(2) transitions, blue-green) and Tb3+ (D-5(4)-F-7(6.5,4.3) transitions, green) respectively. The corresponding luminescence mechanisms are discussed. These phosphors have potential applications in field emission displays.
