慢电子速度成像法结合低温冷离子阱测量镥的电子亲和势（英文）

本文采用低温冷离子阱囚禁的手段累积镥的负离子束流,使得对其电子亲和势的测量变得实际可行.运用慢电子速度成像法获得具有高分辨率的镥负离子的光电子能谱,测得镥的电子亲和势为1926.2(50) cm~(-1)或0.23882(62) eV.此外,还观察到镥负离子的两个激发态.     

Agn(n=2～10)团簇的几何结构和电子特性

应用密度泛函理论中B3LYP/LANL2DZ 方法优化计算并分析了Agn(n=2～10)团簇的基态几何结构及电子性质.同时计算和讨论了银团簇的原子化能、能级分布、能级间隙、电子亲和能和电离势,所得理论计算值与实验值符合较好.研究结果表明:银小团簇的结构不同于块体,且随团簇尺寸大小而相应变化,原子化能和电子亲和势随原子尺寸的增加而增加,团簇的费米能级、电子亲和势和电离势随团簇大小变化具有明显的奇偶振荡特性,并对此作了分析.团簇的电子性质和几何结构之间的密切关系及其随团簇尺寸大小变化的规律,可以从理论上确定团簇的最稳定结构,并可对实验观测结果做出解释.     

5,7'-(亚甲胺基)-二-8-羟基喹啉及其衍生物的密度泛函理论计算

在B3LYP/6-31G(d)水平上对5,7'-(亚甲胺基)-二-8-羟基喹啉及其5种衍生物进行了几何构型全优化,探讨了喹啉不同位H被吸电子基团CN及羟基O被S原子取代对分子电离势(Ip)、电子亲和势(EA)、电荷转移、前线轨道能量和电子光谱等性质的影响.用含时密度泛函理论(TD-DFT)计算了分子在气相及液相的吸收光谱,计算结果与实验值基本符合.取代基对5,7'-(亚甲胺基)-二-8-羟基喹啉锌分子的性质有较大影响.电子亲和势计算表明,该类化合物的电子亲和势较大,都是较好的电子传输材料.     

负离子的故事

负离子广泛存在于气体、液体和固体中,参与很多重要的物理化学过程。负离子的额外电子和中性芯之间的结合很弱,这使得负离子具有显著不同于中性原子和正离子的独特性质,如负离子通常没有激发态。文章首先回顾元素周期表中各原子的电子亲和势、负离子的能级结构,以及相应的测量方法,之后详细介绍最近在过渡族元素负离子方面的研究进展,然后讨论负离子的激光冷却和偶极束缚态,最后总结和展望气相负离子相关研究。     

5,7¢-(亚甲胺基)-二-8-羟基喹啉及其衍生物的密度泛函理论计算

在B3LYP/6-31G(d)水平上对5, 7¢-(亚甲胺基)-二-8-羟基喹啉及其5种衍生物进行了几何构型全优化, 探讨了喹啉不同位H被吸电子基团CN及羟基O被S原子取代对分子电离势(IP)、电子亲和势(EA) 、电荷转移、前线轨道能量和电子光谱等性质的影响. 用含时密度泛函理论(TD-DFT)计算了分子在气相及液相的吸收光谱, 计算结果与实验值基本符合. 取代基对5, 7¢-(亚甲胺基)-二-8-羟基喹啉锌分子的性质有较大影响. 电子亲和势计算表明, 该类化合物的电子亲和势较大, 都是较好的电子传输材料.     

咪唑[4, 5-f] 1, 10-邻菲罗啉及其2-取代芳基衍生物的电子结构与光谱性质

分别采用B3LYP/6-31G(d)和CIS/6-31G(d)方法对咪唑[4, 5-f] 1, 10-邻菲罗啉(ip)及其8种2-取代芳基衍生物的基态(S0)和单重激发态(S1)的几何构型进行了全优化, 并采用含时的度泛函理论(TD-DFT)计算了上述化合物的电子吸收和电子发射光谱. 分析了取代基对咪唑[4, 5-f] 1, 10-邻菲罗啉的电子结构、前线分子轨道、电离势Ip、电子亲和势EA及电子光谱的影响. 计算结果表明, 取代基使8种取代衍生物前线分子轨道(LUMO-HOMO)能隙降低,导致其最大吸收和发射波长均发生了红移. 化合物1～8的跃迁类型均为分子内电荷转移（ICT）跃迁,且1～4和5～8的电子转移方向刚好相反. 溶剂对其电子光谱也有影响, 振子强度增大, 最大发射波长红移. 另外, 8种取代衍生物的电离势降低, 电子亲和势增大, 化合物1~4易于空穴的注入, 5~8易于电子的注入.     

咪唑[4, 5-f] 1, 10-邻菲罗啉及其2-取代芳基衍生物的电子结构与光谱性质

分别采用B3LYP/6-31G(d)和CIS/6-31G(d)方法对咪唑[4, 5-f] 1, 10-邻菲罗啉(ip)及其8种2-取代芳基衍生物的基态(S0)和单重激发态(S1)的几何构型进行了全优化, 并采用含时的度泛函理论(TD-DFT)计算了上述化合物的电子吸收和电子发射光谱. 分析了取代基对咪唑[4, 5-f] 1, 10-邻菲罗啉的电子结构、前线分子轨道、电离势Ip、电子亲和势EA及电子光谱的影响. 计算结果表明, 取代基使8种取代衍生物前线分子轨道(LUMO-HOMO)能隙降低,导致其最大吸收和发射波长均发生了红移. 化合物1～8的跃迁类型均为分子内电荷转移（ICT）跃迁,且1～4和5～8的电子转移方向刚好相反. 溶剂对其电子光谱也有影响, 振子强度增大, 最大发射波长红移. 另外, 8种取代衍生物的电离势降低, 电子亲和势增大, 化合物1~4易于空穴的注入, 5~8易于电子的注入.     

Cu原子掺杂在Al团簇中的结构和电子性质

利用密度泛函理论,对Al_n(n=1～15)团簇中掺杂Cu原子后的双金属团簇进行了研究,在结构优化的基础上,同时计算了双金属团簇的电子性质,即电子亲和能、电离势、Cu原子的Mulliken分布、平均极化率、极化率的各向异性、偶极矩及HOMO-LUMO能隙随团簇尺寸增加时的变化情况. 结果表明,Cu掺杂Al团簇的双金属团簇中也存在幻数结构,团簇的电子性质随团簇尺寸大小出现不规则的奇偶振荡变化. n=13的团簇电子亲和能和电离势与毗邻团簇相比,其变化要大于0.3和0.6 eV.     

紫外光诱导光电子发射负离子源的阈值光电子成像仪设计 (cited: 2)

设计了一套紧凑的光电子成像装置,它包括解离式光电子贴附负离子源、垂直安装的高分辨阈值光电子速度成像装置和线性飞行时间质谱仪．紫外光辐射金属表面诱导低能光电子发射,再通过低能电子贴附超声分子束产生高强度和冷的负离子源．结合这种负离子源和飞行时间质谱-光电子成像仪装置,仪器的质量分辨能达到200左右,能量分辨优于3%(即对1 eV动能的电子,分辨达到30 meV)．此外,使用该实验装置获得了CH₃S^-和S₂^-在611.46 nm下的低能阈值光电子成像结果．同时得到了CH₃S和S₂的更精确的电子亲和势分别为1.8626±0.0020和1.6744±0.0035 eV．初步的结果证明了该装置对研究阈值光电子成像精确测量光电子亲和势非常有效     

Au_n(n=2—9)团簇的几何结构和电子特性

采用密度泛函DFT中的B3LYP方法 ,选择LANL2DZ基组 ,对Aun(n =2— 9)小团簇的各种可能结构进行优化 ,得到了它们的基态平衡结构并计算出其原子化能 .研究表明 :随着团簇尺寸的增大 ,单个原子的平均原子化能逐渐增大 .同时分析了团簇的能级分布、最高占据轨道与最低空轨道之间形成的能级间隙 .计算出了电子亲和能和电离势 ,计算值与实验值非常接近 .最后分析了费米能级、电子亲和能和电离势形成“奇 -偶”振荡效应的原因     

Structural and Near-Infrared Properties of Nd<Superscript>3+</Superscript> Activated Lu<Subscript>3</Subscript>NbO<Subscript>7</Subscript> Phosphor

Undoped and Nd³⁺ doped lutetium niobate phases have been prepared by a conventional solid state reaction method using lutetium acetate and niobium oxide at 1250 °C for 6 h. X-ray diffraction patterns of the 6 mol% Lu₃NbO₇ sample exhibited a cubic fluorite single phase. Phase structure exhibited interesting crystallization behaviour depending on increasing Nd³⁺ concentration which led to a Lu₃NbO₇ single phase formation during the heat treatment process. SEM investigations were also in agreement with the XRD results. Morphologies of Nd³⁺ doped lutetium niobate powders exhibited oval like shapes and grain sizes varied between 0.3 and 5 μm. Near-infrared luminescence properties of Nd³⁺ doped Lu₃NbO₇ were also studied. 1.06 μm laser transition characteristics of Nd³⁺ doped lutetium niobate have been observed. Concentration quenching phenomenon was not detected depending on increasing Nd³⁺ doping concentrations at room temperature.     

Atomic and electronic structures of lutetium oxide Lu2O3

The chemical composition, electronic structure, structure, and physical properties a lutetium oxide Lu₂O₃ film are studied by X-ray photoelectron spectroscopy, ellipsometry, and X-ray absorption spectroscopy. The short-range order in Lu₂O₃ is found to correspond to its cubic modification. The binding energies of the 1s and 2p levels of oxygen and the 4d _5/2 and 4f _7/2 levels of lutetium are 529.2, 5.0 and 7.4, 195.9 eV, respectively. The energy gap determined from the electron energy loss spectrum of the film is 5.9 eV. The electron energy loss spectra have two peaks at 17.4 and 22.0 eV, which can be attributed to the excitation of bulk plasma oscillations. The dispersion of the refractive index is measured by spectral ellipsometry. The refractive index is shown to increase from 1.82 at 1.5 eV to 2.18 at 5.0 eV, and the high-frequency permittivity of Lu₂O₃ is 3.31.     

Growth and the luminescence properties of a lutetium gadolinium garnet doped with Ce3+ and Pr3+ ions

Crystals of lutetium gadolinium garnet solid solutions (Lu_{1 − x} Gd _x )Al₅O₁₂ (0 ≤ x ≤ 0.6) doped with Ce³⁺ and Pr³⁺ ions have been prepared by the horizontal directional crystallization method, and their optical and luminescence properties have been investigated. It has been established that the introduction of gadolinium into the lutetium garnet lattice leads to a decrease in the antisite luminescence (Lu_Al centers) in the UV spectral range and to sensitization of the Ce³⁺ ion luminescence. By contrast, the presence of gadolinium results in the quenching of the Pr³⁺ luminescence due to the nonradiative excitation transfer from Pr³⁺ ions to Gd³⁺ ions.     

Luminescence properties of solid solutions of borates doped with rare-earth ions

The structural and luminescence properties of Lu _x Y_{1 ? x} BO₃ solid solutions doped with Ce³⁺ or Eu⁺³ have been investigated. It has been found that the solid solutions crystallize in the vaterite phase with a lutetium concentration x < 0.5. For a higher lutetium concentration x, the solid solutions contain an additional calcite phase with a content less than 5 wt %. The luminescence spectra are characterized by intensive impurity emission under excitation with the synchrotron radiation in the X-ray and ultraviolet spectral ranges. It has been shown that, as the lutetium concentration x in the Lu _x Y_{1 ? x} BO₃: Ce³⁺ solid solutions increases, the emission intensity smoothly decreases, which is associated with a gradual shift of the Ce³⁺ 5d(1) level toward the bottom of the conduction band, as well as with a decrease in the band gap. It has been established that, in the Lu _x Y_{1 ? x} BO₃: Eu³⁺ solid solutions with intermediate concentrations x, the efficiency of energy transfer to luminescence centers increases. This effect is explained by the limited spatial separation of electrons and holes in the solid solutions. It has been demonstrated that the calcite phase adversely affects the luminescence properties of the solid solutions.     

Molecular-statics simulation of the cerium impurity in LSO crystals

A model is proposed for the Lu₂SiO₅ crystal with cerium impurity, and the defect formation energy, ion relaxation energy, and the defect-induced changes of the Madelung potentials are calculated. The calculations show substitution of the cerium ion for the lutetium ion in the Lu₁ position to be energetically preferred. Fiz. Tverd. Tela (St. Petersburg) 39, 491–492 (February 1997)     

The influence of Pr co-doping on the luminescent properties of Lu2O3:5 mol% Eu films

Uniform and crack free polycrystalline lutetium oxide (Lu₂O₃:(Eu,Pr)) films were fabricated by Pechini sol-gel method combined with the spin-coating technique. X-ray diffraction (XRD) and atomic force microscope (AFM) characterizations indicated that the obtained film was composed of polycrystalline cubic Lu₂O₃ phase with an average grain size around 30 nm. The photoluminescence(PL) spectra and decay performances of the Lu₂O₃:5 mol% Eu films co-doped by 0-0.5 mol% Pr³⁺ with different concentrations were characterized. It was found that the afterglow was reduced obviously due to the introduction of 0-0.5 mol% Pr³⁺ in the Lu₂O₃:5 mol% Eu films coupled by decrease in the emission intensity at 612 nm. The mechanism of afterglow diminishing was discussed based on the thermoluminescence measurements.     

Synthesis, characterization, and luminescent properties of Lu2O3:Eu phosphors

Eu-doped lutetia (Lu₂O₃:Eu) nano-phosphors were synthesized by the sol-gel combustion process from a mixed aqueous solution of europium and lutetium nitrates, using organic glycine as the fuel. Powder X-ray diffraction shows that cubic Lu₂O₃:Eu crystallites are directly obtained by the sol-gel combustion process without further calcination. Electron microscopy reveals that the as-prepared phosphors are agglomerated and have a fluffy, fine, and porous morphology, consisting of primary particle size of 8-10 nm. The excitation spectrum is characterized by three dominant bands centered at 395, 466, and 534 nm, respectively. Both the photoluminescent and radioluminescent spectra are very similar and exhibit intense emission peaks centered at 612 nm due to ⁵D₀→⁷F₂ transition of Eu³⁺ ions. The energy transfer from Lu₂O₃ host to Eu³⁺ activator is more efficient in the case of calcined phosphors than for the as-prepared phosphors due to their improved lattice perfection.     

Electron paramagnetic resonance study of exchange coupled Ce3+ ions in Lu2SiO5 single crystal scintillator

The Ce³⁺ ions incorporation inside lutetium oxyorthosilicate (Lu₂SiO₅) single crystals was studied by electron paramagnetic resonance. Already known Ce1 and Ce2 centers originating from the lattice peculiarity allowing two lutetium sites coordinated by different number of the oxygen ions were detected. Remarkably, for the Ce2 center, the determined g² tensor is asymmetric and could not be diagonalized as compared to the Ce1 center, for which the three principal values and corresponding axes orientation have been determined and reported previously. Besides, the much weaker resonance lines found in spectra close to those coming from the Ce1 and Ce2, and following them under crystal rotation with respect to the direction of an external magnetic field, have been revealed as well. They were classified as doublets produced by the exchange coupled Ce³⁺ ions, creating the Ce1–Ce1, Ce2–Ce2 and Ce1–Ce2-like dimers. The corresponding spin–spin coupling constants were estimated. They are in the range 0.04–0.4 cm⁻¹. The Ce1, Ce2 and total dimer centers populations were calculated as 89%, 4.5% and 6.5%, comparing integral intensities of corresponding resonance lines.     

Luminescence spectroscopy of excitons and antisite defects in Lu3Al5O12 single crystals and single-crystal films

The nature of the intrinsic luminescence of the lutetium aluminum garnet Lu₃Al₅O₁₂ (LuAG) has been analyzed on the basis of time-resolved spectral kinetic investigations upon excitation of two model objects, LuAG single crystals and single-crystal films, by pulsed X-ray and synchrotron radiations. Due to the differences in the mechanisms and methods of crystallization, these objects are characterized by significantly different concentrations of Lu_Al antisite defects. The energy structure of luminescence centers in LuAG single crystals (self-trapped excitons (STEs), excitons localized near antisite defects, and Lu_Al antisite defects) has been established. For single-crystal LuAG films, grown by liquid-phase epitaxy from a Pb-containing flux, the energy parameters of the following luminescence centers have been determined: STEs in regular (unperturbed by the presence of antisite defects) sites of the garnet lattice and excitons localized near Pb²⁺ ions. The structure of the luminescence centers, related to the background emission of impurity Pb²⁺ ions, has also been established in the UV and visible ranges. It is suggested that, in contrast to the two-halide hole self-trapping, a self-trapped state similar to STEs in simple oxides (Al₂O₃, Y₂O₃) is formed in LuAG; this state is formed by self-trapped holes in the form of singly charged O^? ions and electrons localized at excited levels of Lu³⁺ cations.     

Transition energies of atomic lawrencium

Transition energies of the superheavy element lawrencium, including the ionization potential, excitation energies and electron affinities, are calculated by the intermediate Hamiltonian coupled cluster method. A large basis set (37s31p26d21f16g11h6i) is used, as well as an extensive P space (6s5p4d2f1g). The outer 43 electrons are correlated. Accuracy is monitored by applying the same approach to lutetium, the lighter homologue of Lr, and comparing with experimentally known energies. QED corrections are included. The main goal is to predict excitation energies, in anticipation of planned spectroscopy of Lr. The ground state of Lr is , unlike the of Lu. Predicted Lr excitations with large transition moments in the prime range for the planned experiment, 20 000–30 000 cm^-1, are 7p→8s at 20 100 cm^-1 and 7p→7d at 28 100 cm^-1. The average absolute error of 20 excitation energies of Lu is 423 cm ^-1, and the error limits for Lr are put at 700 cm^-1. The two electron affinities measured recently for Lu are reproduced within 55 cm^-1, and a third bound state of Lu^- is predicted.