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1.
Feng Zhang Zhisong Xiao Lu Yan Fang Zhu Anping Huang 《Applied Physics A: Materials Science & Processing》2010,101(4):777-780
Er3+ and Dy3+ codoped tellurite glasses have been synthesized. Five emission bands in the PL spectrum under 325 nm pumping were observed.
Three of them correspond to Er3+ and the other two correspond to Dy3+, respectively. The PL spectrum revealed that the intensity of Dy3+ characteristic emission was enhanced as Er3+ concentration increased while keeping Dy3+ concentration constant. Due to small mismatch between the energy level of Er3+:4F7/2 and Dy3+:4F9/2 resonant energy was possibly transferred between them. This process can give rise to an enhancement of the PL intensity of
484 and 574 nm from Dy3+. The PL spectra of these glasses cover the blue, green and red wavelength range and the intensities of those emission bands
could be controlled by adjusting the concentration of relevant rare-earth ions. These glasses with the controllable CIE coordinates
might be a potential candidate for the widely realistic application such as solid-state white lighting and multicolor display. 相似文献
2.
The super-exchange interaction parametersI(Fe, Cr) of Fe3+ and Cr3+ in iron doped rate-earth orthochromitesRCr0.99Fe0.01 O3 (R=La, La0.5Nd0.5, Nd, Sm, Gd, Dy, Y, Er, Yb or Lu) have been obtained from57Fe magnetic hyperfine structure measurementsvia the Mössbauer effect.The dependence of the experimental valuesI(Fe, Cr) on the Fe–O–Cr average superexchange angle (depending upon the relative size of the rare-earth (RE) ionR
3+) is well described by the equationI(d5, d
N
) =
N
+
N
cos +
N
cos2 .Within the accessible range of super-exchange angles 142°156°, the Fe3+–O2––Cr3+ interaction is negative (antiferromagnetic). However, a theoretical analysis predicts a sign reversal forI(Fe, Cr.) at about 162° and thus ferromagnetic character of the interaction between 162° and 180°.The spin-only super-exchange interaction integrals fore
g andt
2g electrons, separately, are also calculated. Their angular dependence is accounted for by the behaviour of the antiferromagnetic kinetic and ferromagnetic potential exchange which are of different character when passing from 180° to 90° super-exchange geometry. The magnitude and the sign of the spin-only super-exchange integral for an arbitrary 3d cation, pair is predicted. 相似文献
3.
《Nuclear Physics A》1986,451(4):701-727
The mechanism of the reaction 3He + p → p + p + d is studied by making use of the ITEP 80 cm liquid-hydrogen bubble chamber exposed to a beam of 5 GeV/c 3He nuclei. The reaction cross section is equal to 20.6 ± 0.3 mb. The phase-space regions associated with quasifree scattering (QFS) and final-state interactions (FSI) are selected. Angular, mass and momentum distributions of the reaction products are obtained in the entire kinematically allowed range. The experimental data in the QFS region are compared with theoretical calculations based on the simplest pole-diagram approximation. The 3He and deuteron wave functions (WF) correspond to the realistic RSC potential. The D-wave components of these WF are taken into account. The absolute value of the cross section and shape of the distributions are described as a whole reasonably well within the frame of the model considered in the kinematical region where FSI may be neglected. But at large spectator momenta there is an essential disagreement. The possible reasons for this are discussed. 相似文献
4.
Spectroscopic properties and excited-state absorption (ESA) of Ti3+ doped YAlO3 are investigated in detail. The fluorescence band is centered at 623 nm with a room-temperature lifetime of 11.4 s and a quantum efficiency nearby one. Till now laser action could not be detected because of strong excited-state absorption into a charge transfer band located 45 500 cm–1 above the Ti3+ ground state. At the Ar-laser pump wavelength the ESA cross-section is determined to be ESA=1×10–18 cm2. This value is a factor of 44 higher than the ground-state absorption cross-section. Consequently the pumping efficiency is decreased by one or two orders of magnitude. The Ti:YAlO3 results are compared with the spectroscopic data of Ti:Al2O3.Dedicated to Prof. Dr. Herbert Welling on the occasion of his 60th birthday 相似文献
5.
The possibility of combustion synthesized Ho3+–Tm3+–Yb3+ codoped Y2O3 phosphor as temperature sensor using fluorescence intensity ratio (FIR) technique under a 980 nm excitation has been reported. The variation in FIR of blue upconversion emissions generated from two closely spaced levels of the Tm3+ and Ho3+ ions (1G4 and 5F3) as a function of temperature has been monitored up to 703 K. The maximum relative sensitivity has been found to be 3.38 × 10?3 K?1 which indicates that the present phosphor material can play a vital role for high optical thermometric purpose. The results imply that the FIR of two closely spaced levels of two different rare earth ions can also be used as temperature sensor. 相似文献
6.
The CsCdBr3∶U3+ crystal was grown by the Bridgman technique from the starting materials CsBr, CdBr2, and UBr4. X-ray check showed that the sample crystallized in the CsNiBr3 structure. Under selective excitation at low temperature, the emission spectra and the fluorescence decay curve were measured and discussed. 相似文献
7.
Y. Y. Zhang L. W. Yang C. F. Xu J. X. Zhong C. Q. Sun 《Applied physics. B, Lasers and optics》2010,98(2-3):243-247
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. 相似文献
8.
Asatryan G. R. Edinach E. V. Uspenskaya Yu. A. Babunts R. A. Badalyan A. G. Romanov N. G. Petrosyan A. G. Baranov P. G. 《Physics of the Solid State》2020,62(11):2110-2115
Physics of the Solid State - In yttrium aluminum garnet (YAG) crystals containing terbium and cerium impurities, along with the main EPR signals of Tb3+ and Се3+ ions located in the... 相似文献
9.
10.
Upconversion Luminescence of Eu3 + in NaYbF4∶ Tm3 + , Eu3 +Nanocrystals Induced by 980 nm Excitation
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利用水热法制备得到NaYbF4∶0.01%Tm3+,20% Eu3+上转换材料,利用X射线衍射分析、扫描电子显微镜及光谱测试技术分别对其进行了结构、形貌以及光谱性质的表征.在980 nm近红外激光激发下,得到了Eu3+的可见到紫外范围的上转换荧光发射.分析表明:共掺杂NaYbF4纳米材料中Tm3+到Eu3+离子的能量传递对布居Eu3+离子的激发态能级,获得Eu3+的上转换发光起着至关重要的作用.另外,在实验中首次获得了Eu3+对应于3P0→7Fj(j=0,1,2)能级跃迁的上转换光发射. 相似文献
11.
Constantin Crâciun 《光谱学快报》2013,46(10):579-590
Abstract The influence of octahedral replacement of Al3+ by Fe3+ on the infrared spectra of montmorillonites in the domain of OH vibrations is presented. The obtained results suggest that in the domain of OH-bending vibration, the absorption band from 870 cm?1 (Al3+ -OH-Fe3+) can not be detected in the spectra of montmorillonites when the octahedral Fe3+ content is below 0.10-0.15 (per half unit cell) In the domain of OH-stretchtng, the increasing Fe3+ -for-Al3+ substitution in the dioctahedral series of smectites causes a continous shift of the absorption band ascribed to M3+ - OH - M3+ vibrations to lower frequencies. 相似文献
12.
《Solid State Communications》1986,59(4):187-191
The conductivity and thermoelectric power of samples from two different NbS3+δ compounds have been measured in wide ranges of temperatures below 430K. The compound with the larger excess of sulfur was found to be stable upon treatement with CS2 and heat treatment. Its conductivity exhibits two anomalies, a sharp one around 360K and a broad one around 150K. The results obtained for these compounds are compared with the results reported in the literature for other NbSx compounds and for TaS3. 相似文献
13.
Doris Vokurková Ji?ina Vávrová Ji?í ?inkora Alena Stoklasová Václav Bláha Martina ?ezá?ová 《Radiation measurements》2010,45(9):1020-1023
The effect of lower doses (0.5–3.0 Gy) of gamma radiation on radiosensitivity of CD3?/CD8+ NK cells subpopulation isolated from the peripheral blood of healthy volunteers was studied 48 h after the irradiation. Only a subtle increase in terms of induction of apoptosis (A+ cells), was observed in Annexin positive CD3?/CD8+ NK cells. The assessment of the relative presence of CD3?/CD8+ NK cells in Annexin negative populations of lymphocytes considerably contributes to the elimination of individual variability and could be useful in biodosimetry.Living CD3?/CD8+; Annexin negative NK cells were analyzed using five-color flow cytometry 16 h after irradiation by the doses of 1–10 Gy. The study was carried out on NK cells subsets CD3?/CD8? CD16+, CD56 (dim) and CD56 (bright). NK cells characterized with their low-density expression of CD56 (dim) are more cytotoxic and express CD16. Those with high-density expression of CD56 (bright) are known for their capacity to produce cytokines following activation of monocytes but their natural cytotoxicity is low; they are classified as CD16? or CD16 (dim). A dose-depending decrease in the relative presence of CD3?/CD8+ NK cells was observed 16 h after ionizing radiation (1–10 Gy). The decrease was highly pronounced in CD56 (bright) subset of NK cells and this subpopulation was considered as the most radiosensitive one. Unfortunately, the most radiosensitive subpopulation of NK cells – CD56bright cannot be used as a biodosimetric marker due to its insufficient amount in peripheral blood. 相似文献
14.
Hexagonal YPO4 phosphors doped with Eu3+/Dy3+ and co-doped with Ce3+ were synthesized by a hydrothermal route assisted using lauric acid as a capping agent. The prepared phosphors were characterized by transmission electron microscopy, infrared spectroscopy, powder X-ray diffraction and photoluminescence spectra. YPO4: Eu3+ gives two red emission peaks at 587 and 610?nm corresponding to 5D0→7F1 and 5D0→7F2 transitions, respectively. YPO4: Dy3+ exhibits two emission peaks at 485?nm (blue) and 575?nm (yellow) corresponding to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions, respectively. Ce3+ ions enhanced the emission intensity as a co-dopant in both phosphors. Moreover, the effect of γ-radiation in the dose range 5–300?kGy on the photoluminescence behaviour of YPO4:Eu3+,Ce3+ and YPO4:Dy3+,Ce3+ was also investigated. Quenching of emission intensity, after irradiation at 5 and 300?kGy, was observed in both the phosphors due to loss of excess energy through a non-radiative relaxation process. 相似文献
15.
用水热法合成了Y0.8-x-yF3∶Gdx3+,Yb0.23+,Tmy3+纳米晶的上转换发光材料。在典型的Y0.595F3∶Gd0.2003+,Yb0.2003+, Tm0.0053+纳米微晶中,在980 nm激光激发下,观察到了Tm3+的紫外、紫色上转换发射明显增强和来自于Gd3+的6D9/2、6IJ、6P5/2及6P7/2能级到基态8S7/2能级的紫外发射。通过比较Y0.8-x-yF3∶Gdx3+ ,Yb0.23+,Tmy3+纳米晶样品的上转换发光性质以及Tm3+和Gd3+中一些激发态的能级寿命,借助于能级图描述了Yb3+-Tm3+-Ga3+之间的有效的能量传递过程。 相似文献
16.
GdBO3:Pr3+,Yb3+中Pr3+到Yb3+的能量传递及发光性质 总被引:1,自引:1,他引:0
采用高温固相法制备了一系列单掺或双掺Pr3+和Yb3+的GdBO3材料,分别测试分析了材料的物相结构和发光性质。在446 nm蓝光( Pr3+:3 H4→3 P2)激发下,检测到Yb3+的近红外特征发射,表明样品中存在Pr3+到Yb3+的能量传递。 Pr3+的掺杂浓度一定时,样品的发光会随着Yb3+掺杂浓度的改变而发生变化。通过对比不同掺杂情况下Pr3+:3 P0能级的衰减曲线,发现随着Yb3+的掺杂浓度的增加,该能级的荧光寿命不断缩短;同时利用不同条件下的衰减特性计算得出不同 Yb3+掺杂浓度样品的能量传递效率。用 Inokuti-Hirayama模型分析表明Pr3+-Yb3+能量传递类型为偶极子-偶极子相互作用。 相似文献
17.
Jung-Hyun Cho Michael Bass Suresh Babu Janet M. Dowding William T. Self Sudipta Seal 《Journal of luminescence》2012,132(3):743-749
The effects of Yb3+ doping on up conversion in Yb3+–Er3+ co-doped cerium oxide nanocrystals are reported. Green emission around 545 and 560 nm attributed to the 2H11/2, 4S3/2→4I15/2 transitions and red emission around 660 and 680 nm due to 4F9/2→ 4I15/2 transitions under 975 nm excitation were studied at room temperature. Both green and red emission intensities increase as the Yb3+ concentration increases from 0%. Emission strength starts to decrease after the Yb3+ concentration exceeds a critical amount. The green emission strength peaks around 1% Yb3+ concentration while the red emission strength peaks around 4%. An explanation of competition between different decay mechanisms is presented to account for the luminescence dependence on Yb3+ concentration. Also, the application of up converting nanoparticles in biomedical imaging is demonstrated. 相似文献
18.
A. M. Gorbatov A. V. Germanov D. V. Nechaev P. V. Komarov P. Yu. Nikishov 《Physics of Atomic Nuclei》2000,63(3):431-439
A collective adiabatic approach is used to explore the total and differential cross sections for the reactions d + d → p + 3H and d + d → n + 3He at incident-deuteron energies of up to 6 MeV. All substantially contributing partial waves of order not higher than that of G waves are taken into account. The experimental value of the difference of the cross sections for the above mirror reactions is reproduced theoretically under the assumption that nuclear forces obey the condition of isotopic invariance. The positions and amplitudes of the maxima in the calculated total cross sections virtually coincide with those of the corresponding experimental values. It is shown that, around the maxima of the cross sections under study, dominant contributions to them come from the P wave. The sensitivity of observables to the parameters of nucleon-nucleon interaction is analyzed. 相似文献
19.
《Journal of luminescence》1987,37(1):1-8
Ion exchange techniques were used to substitute Cr3+ and Rh2+ ions for the sodium ions present in sodium-beta″-alumina single crystals. The optical absorption and fluorescence spectra were obtained and the fluorescence lifetimes measured for both types of samples. In each case the emission consisted of two bands having significantly different decay times. The temperature dependences of the fluorescence intensities and lifetimes were measured for these bands. The results are interpreted in terms of the energy level structures of these ions in different crystal field sites in this host lattice and the diffusion of ions in the conduction plane which changes these sites. 相似文献
20.
First-principles calculations employing density functional theory are performed to study ionic crystal structures of NO+NO3?. The pressure dependences of enthalpy, structural parameters, and electronic band gap are investigated for the two experimentally reported phases of NO+NO3?. It is found that these two phases have comparable densities for P<25 GPa and are thus competing ones that may be obtained through different pathways. Moreover, one of the two phases is unlikely the previously proposed orthorhombic P21cn structure. The trend of pressure dependence of the band gap is typical of that for ionic crystals. This study provides insight into different experimental findings. 相似文献