Time-Resolved Vacuum Ultraviolet Spectroscopy of Er<Superscript>3+</Superscript> Ions in the SrF<Subscript>2</Subscript> Crystal

The photoluminescence and photoexcitation spectra as well as the luminescence decay kinetics of Er³⁺ ions in the visible ultraviolet and vacuum ultraviolet (VUV) regions have been studied by the method of low-temperature, time-resolved VUV-spectroscopy on excitation by synchrotron radiation. In the VUV spectral region of the luminescence of SrF₂:1% Er³⁺, the 146.5-nm band with a time of decay of less than 0.6 nsec was revealed together with the well-known emission band at 164.3 nm (decay constant in the microsecond range). Its possible nature is discussed. The specific features of the formation of photoexcitation spectra of the f-f and f-d transitions in the Er³⁺ ion are considered. Competition between the processes of excitation of f-f and d-f luminescence has been revealed. It manifests itself in the inverse relationship of their photoexcitation spectra in a range of energies of incident photons that are close to the position of the 4fⁿ⁻¹5d configuration levels. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 519–523, July–August, 2005.     

突破间接带局限创新Si基激光器

Si基高效发光与受激光发射是Si基光子学突破性发展的关键课题,它的实现对Si基微电子学的发展有深远的重大意义．由于受到天然Si材料间接带能带结构的限制,Si材料的发光效率极低,更谈不上可实现受激光发射,人工改性就成为当代研究、开拓的主要途径．新的Si基直接带体材料(如β-FeSi2等)的探索,Ge／Si量子阱、超晶格、量子点的能带工程介观改性,子带发光跃迁的探索,异类元素插入短周期超晶格中的化学键改性,以及SiO2高浓度nc-Si的生成和高激活度稀土离子的掺入发光等已开展了多途径的研究,不同程度上取得了重要的进展,一种MIS结构电子隧道注入高效发光器件已在SiO2：RE MOS结构中实现．运用激光器件物理的深入设计和新的器件技术的引入,可以预计本世纪初叶,对实现Si基激光器的奢望将会成为现实,无疑它对Si基光子学、Si基集成光电子学乃至信息高科技的发展将作出历史性的巨大贡献．     

Rare-Earth–Transition-Metal Organic–Inorganic Hybrids Based on Keggin-type Polyoxometalates and Pyrazine-2,3-dicarboxylate

Five rare-earth–transition-metal (RE–TM) heterometal organic–inorganic hybrids based on Keggin-type silicotungstates and mixed ligands H2pzda (pzda=pyrazine-2,3-dicarboxylate) and en (en=ethylenediamine) (enH2)[Cu(en)2(H2O)]2{[Cu(en)2][Cu(en)2(H2O)][(α-SiW11 O39)RE(H2O)(pzda)]}2⋅n H2O (n≈4; RE=YIII ( 1 ), DyIII ( 2 ), YbIII ( 3 ), and LuIII ( 4 )) and [Cu(en)2(H2O)]2{[Cu(en)2]2[Cu(pzda)2][(α-H2SiW11O39)Ce(H2O)]2}⋅n H2O ( 5 ; n≈8) have been hydrothermally synthesized and structurally characterized. Compounds 1–5 all contain the dimeric mono-RE substituted Keggin [RE(α-SiW11O39)]210− subunits linked by H2pzda ligands. Interestingly, 1–4 exhibit discrete structures, in which the H2pzda ligand acts as a tetradentate ligand to bind the RE and Cu cations, whereas 5 displays a 1D double-chain architecture, in which the H2pzda ligand adopts a new pentadentate mode to connect the Ce and Cu cations. To our knowledge, 1–5 represent the first monovacant Keggin-type silicotungstates containing both RE–TM heterometals and mixed ligands. The luminescence of 2 is derived from the combination of the DyIII cations and H2pzda ligands, whereas the luminescence properties of 1 and 3–5 are attributable to the H2pzda ligands.     

Spectral analysis of rare-earth elements in ash of sapropel and its fractions

Quantitative atomic emission spectral analysis was used to study the rare-earth content in sapropel and the rare-earth distribution over the isolated fractions. The conditions for determination of Ce, Y, and La (analytical lines, arc discharge current, exposure time) were selected empirically. We calculated the metrological characteristics of the proposed technique. We have shown that in Tyurin fractionation, the nonhydrolyzable residue fraction has the highest concentrations of these elements. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 273–276, March–April, 2009.     

稀土席夫碱配合物催化己内酯可控开环聚合

 通过稀土氯化物与席夫碱钠盐的交换反应制备了一系列以 3,5-二叔丁基水杨醛缩苯胺为配体的稀土席夫碱配合物. 对其中的钕席夫碱配合物进行了 X射线单晶衍射分析, 发现其单晶结构为五角双锥构型, 所得席夫碱稀土配合物可以单组分催化 ?-己内酯开环聚合. 深入研究了钕席夫碱配合物催化己内酯的开环聚合机理, 考察了不同聚合条件对单体转化率、产物分子量及分子量分布的影响. 结果表明, 该聚合反应速率为一级, 聚合反应具有较好的可控性. 聚合物端基分析表明, 聚合反应以配位-插入机理进行.     

NaLa(MoO4)2∶Eu3+的水热调控合成与发光特性研究

采用水热法合成了不同粒径的NaLa(MoO₄)₂∶Eu³⁺微晶.通过调节乙二醇浓度和反应时间,研究了NaLa(MoO₄)₂∶Eu³⁺微晶的形貌演变过程,在水热条件下180 ℃反应16 h获得了均一梭子形NaLa(MoO₄)₂∶Eu³⁺微晶,其晶粒长度约为2.0 μm.荧光光谱分析表明,Eu³⁺取代了NaLa(MoO₄)₂中La³⁺的格位, Eu³⁺在613 nm处红光发射(⁵D₀–⁷F₂跃迁)的浓度猝灭机理是电偶极-电四极相互作用,并发生了Eu³⁺( ⁵D₁ ) + Eu³⁺(⁷F₀ )→ Eu³⁺( ⁵D₀ ) + Eu³⁺(⁷F₃) 交叉弛豫,由此导致浓度猝灭. 关键词： 钼酸盐 水热法 稀土离子 发光     

Sr0.6Ba0.2Ca0.2Al2O4 ∶Eu,Dy的制备与长余辉发光性能研究

采用高温固相法制备了Ca,Ba共掺的Sr_0.6Ba_0.2Ca_0.2Al₂O₄ ∶Eu²⁺_0.01, Dy³⁺_0.02和单掺Ba的Sr_0.6Ba_0.4Al₂O₄ ∶Eu²⁺_0.01, 关键词： 长余辉 铝酸锶 稀土掺杂 陷阱能级     

Sums Over States of the Atoms and Singly and Doubly Charged Ions of Rare-Earth Elements

The sums over states of the atoms and singly and doubly charged ions of rare-earth elements that are required for a theoretical study of thermochemical processes in high-temperature plasma spectral sources are calculated in the temperature range 2500–12,000 K.     

Understanding the influence of nanoenvironment on luminescence of rare-earth ions

This paper presents an overview of the recent results on upconversion and photoluminescence of rare-earth ions in nanoenvironments. The role of the rare-earth ion concentration, crystal size and crystal phase on the up and downconversion emission of rare-earth ions in oxide nanocrystals and their underlying mechanisms are discussed. It is also found that the luminescence lifetime of the excited state rare-earth ions is sensitive to the particle crystalline phase and size. The analysis suggests that the modifications of radiative and nonradiative relaxation mechanisms are due to local symmetry structure of the host lattice and crystal size respectively     

Scattering loss in Nd-doped silica based optical fibers

Rare-earth doped fibers suffer from relatively high attenuation in comparison to conventional communication fibers. In order to improve the properties of such fibers, understanding of the mechanisms involved in scattering effects is of great importance. The effect of Nd-doping, Al-codoping and of the drawing temperature on the scattering effect was investigated for several different optical fibers. To this end a measuring setup was realized which allows absolute measurements of the scattering coefficient at different positions along a fiber. Also separation of total attenuation and scattering effects is possible. The presented results indicate scattering effects as primary source for increased attenuation compared with undoped fibers.