Preparation and Luminescence Behavior of CaSiO3：Eu^3＋（Bi^3＋）

CaSiO3：Eu0.08^3＋Bi0.002^3＋ with a monoclinic perovskite structure was synthesized by using sol-gel method, and its luminescence characteristics were investigated. From the excitation spectrum, it can be seen that the main peaks located at 238,396,415,437 and 359 nm correspond to the charge-transfer band of Eu^3＋-O^2- , the absorption transitions of ^7F0.1→^3L6, ^7F0→^5D3, ^7F1→^5D3 of Eu^3＋ ions, and ^3P1→^1S0 of Bi^3＋ ions, respectively. When the samples were excited with a light of wavelength 359 or 395 nm, it can be seen from the emission spectrum that the electronic dipole transition located at 609 nm corresponding to ^5D0→^7F2 of Eu^3＋ ions was stronger than the magnetic dipole transition located at 587 nm corresponding to ^5D0→^7F1 of Eu^3＋ ions, which shows that more Eu^3＋ ions were located in nonreversion center lattices. The energy transfer from Bi^3＋ ions to Eu^3＋ ions in the phosphor was also discussed. The results show that Eu^3＋ ions could be well sensitized by ^3＋ions, and the energy-transfer pattern between Bi^3＋ ions and Eu^3＋ ions was resonance energy transfer.     

磁性荧光双功能复合纳米粒子Fe3O4@SiO2@ZrO2:Tb3+的合成和表征

通过原位反应合成法成功合成了一种新型水溶性的磁性荧光复合纳米粒子Fe₃O₄@SiO₂@ZrO₂:Tb³⁺,并通过扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)、红外光谱仪(FT-IR)、磁性测试仪和荧光(PL)光谱对其形貌、尺寸、相组成、磁性和荧光性能进行了表征。 结果表明,核(Fe₃O₄@SiO₂)壳(ZrO₂:Tb³⁺)结构组成的磁性荧光复合纳米粒子具有超顺磁性,其饱和磁化强度达到36 emu/g,并且在494 nm(⁵D₄→⁷F₆)、549 nm(⁵D₄→⁷F₅)、587 nm(⁵D₄→⁷F₄)和625 nm(⁵D₄→⁷F₃)处具有4个Tb³⁺特有的荧光发射光谱带峰值。 磁性荧光双功能的复合纳米粒子在生物医学领域具有潜在的应用价值。     

2, 4, 6-三甲基苯甲酸与5, 5'-二甲基-2, 2'-联吡啶构筑的系列镧系超分子配合物的晶体结构、热分解机理和性能

Six ternary lanthanide complexes formulated as [Ln(2, 4, 6-TMBA)₃(5, 5'-DM-2, 2'-bipy)]₂ (Ln = Pr 1, Nd 2, Sm 3, Eu 4, Gd 5, Dy 6; 2, 4, 6-TMBA = 2, 4, 6-trimethylbenzoate; 5, 5'-DM-2, 2'-bipy = 5, 5'-dimethyl-2, 2'-bipyridine) have been synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, etc. The results of crystal diffraction analysis show that complexes 1–6 are binuclear units, crystallizing in the triclinic Pī space group. Complexes 1–5 are isostructural, and each of the central metal ions has a coordination number of 9. The asymmetric unit of complexes 1–5 consists of one Ln³⁺, one 5, 5'-DM-2, 2'-bipy ligand, and three 2, 4, 6-TMBA^- moieties with three coordination modes: chelation bidentate, bridging bidentate, and bridging tridentate. The coordination geometry of Ln³⁺ is distorted monocapped square antiprismatic. The binuclear units of complexes 1–5 form a one-dimensional (1D) supramolecular chain along the c-axis via π–π stacking interactions between the 2, 4, 6-trimethylbenzoic acid rings. The 1D chains are linked to form a supramolecular two-dimensional (2D) sheet in the bc plane via π–π stacking interactions between the pyridine rings. Although the molecular formulae of complex 6 and complexes 1–5 are similar, the coordination environment of the lanthanide ions is different in the two cases. The asymmetric unit of complex 6 contains a Dy³⁺ ion coordinated by a bidentate 5, 5'-DM-2, 2'-bipy and three 2, 4, 6-TMBA^- ligands adopting bidentate and bridging bidentate coordination modes. The Dy³⁺ metal center has a coordination number of 8, with distorted square antiprismatic molecular geometry. The binuclear molecule of 6 is assembled into a six-nuclear unit by π–π weak staking interactions between two 5, 5'-DM-2, 2'-bipy ligands; then, adjacent six-nuclear units form a 1D chain via offset π–π interactions between 5, 5'-DM-2, 2'-bipy ligands on different adjacent units. The adjacent 1D chains are linked by C―H···O hydrogen bonding interactions to form a 2D supramolecular structure. The thermal stability and thermal decomposition mechanism of all the complexes are investigated by the combination of thermogravimetry and infrared spectroscopy (TG/FTIR) techniques under a simulated air atmosphere in the temperature range of 298–973 K at a heating rate of 10 K·min^-1. Thermogravimetric studies show that this series of complexes have excellent thermal stability. During the thermal decomposition of the complex, the neutral ligand is lost first, followed by the acid ligand, and finally, the complex is decomposed into rare earth oxides. The three-dimensional infrared results are consistent with the thermogravimetric results. The photoluminescence spectra of complex 4 show the strong characteristic luminescence of Eu³⁺. The five typical emission peaks at 581, 591, 621, 651, and 701 nm correspond to the ⁵D₀ → ⁷F₀, ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂, ⁵D₀ → ⁷F₃, and ⁵D₀ → ⁷F₄ electronic transitions of Eu³⁺, respectively. The emission at 621 nm is due to the electric dipole transition ⁵D₀ → ⁷F₂, while that at 591 nm is assigned to the ⁵D₀ → ⁷F₁ the magnetic dipole transition. The lifetime (τ) of complex 4 is calculated as 1.15 ms based on the equation τ = (B₁τ₁² + B₂τ₂²))/(B₁τ₁ + B₂τ₂), and the intrinsic quantum yield is calculated to be 45.1%. Further, the magnetic properties of complex 6 in the temperature range of 2–300 K are studied under an applied magnetic field of 1000 Oe.     

2-甲基呋喃分子激发态超快非绝热动力学

Excited-state dynamics of 2-methyl furan has been studied by femtosecond time-resolved photoelectron imaging. The molecule 2-methyl furan was simultaneously excited to the n=3 Rydberg series of S₁[¹A"(π3s)], ¹A'(π3p_x), ¹A"(π3p_y) and ¹A"(π3p_z) and the valence state of ¹A'(ππ^*) by two 400 nm photons and subsequently probed by two 800 nm photons. The average lifetime of the Rydberg series and the valence state was measured to be on the time scale of 50 fs by the time-dependent ion yield of the parent ion. Ultrafast internal conversions among these excited states were observed and extracted from the time-dependences of the photoelectron kinetic energy components of these excited states in the photoelectron kinetic energy spectra. Furthermore, it is identified that the ¹A'(ππ^*) state might play an important role in internal conversions among these excited states. The Rydberg-valence mixings, which result in numerous conical intersections, act as the driving force to accomplish such ultrafast internal conversions.     

荧光粉Ba5-3x/2B4O11∶xEu3+的制备及发光性能

采用高温固相烧结法成功制备了Ba_5-3x/2B₄O₁₁∶xEu³⁺(x=0.02~0.22)荧光粉,利用XRD和SEM等对荧光粉进行了结构和形貌表征。 在激发波长为393 nm的条件下,发射峰(596、621、657和706 nm)与Eu³⁺的⁵D₀-⁷F_J(J=1,2,3,4)电子跃迁相对应,其中621 nm最强发射峰由Eu³⁺离子⁵D₀→⁷F₂电偶极跃迁造成。 文章还研究了Eu³⁺掺杂浓度对Ba_5-3x/2B₄O₁₁∶xEu³⁺发光性能的影响,结果表明,荧光粉的发光强度随着Eu³⁺掺杂量的增加呈现先增大后减小的趋势,Eu³⁺最佳掺杂量为0.16。     

Fukui Functions for the Temporary Anion Resonance States of Be~-, Mg~-, and Ca~-

In this work,the Fukui functions of the two ~2P resonance states of Be,a ~2P resonance state of Mg~–,and a ~2D resonance state of Ca~– have been determined.The trajectories of these resonance states,in conjunction with the complex rotation of the Hamiltonian,were used to determine their wave functions.The electron densities,Fukui functions,and values of the hyper-radiusr~2were computed from these wave functions.The Fukui functions have negative regions in the valence shell in addition to the inner shell regions,indicating screening effects of the outer temporary electron.Selected configuration interactions with up to quadruple excitations were used along the trajectories and for computing the final wave function.Based on this data,the densities,Fukui functions,andr~2were calculated.     

卤代芳香族羧酸与含氮配体合成镧系配合物的结构、热化学和荧光性质（英文）

采用室温溶液挥发法合成了五种结构新颖的镧系配合物,其结构通式为[Ln(2,4-DFBA)₃(phen)]₂ (Ln=Sm 1, Eu2, Er 3, 2,4-DFBA为2,4二氟苯甲酸的简写,phen为1,10-菲啰啉的简写),[Ln(2-Cl-6-FBA)₂(terpy)(NO₃)(H₂O)]₂ (Ln=Tb4, Dy 5, 2-Cl-6-FBA为2-氯-6-氟苯甲酸的简写, terpy为2,2’:6’2’’-三联吡啶的简写)。五个配合物可以分为两个系列,使用不同的镧系离子作为中心离子。通过X射线单晶分析,5种配合物均属于单斜晶系,空间群为P21/n。配合物1,2和配合物3虽然具有相同的分子通式,但配位方式明显不同,形成了前者为9配位的松饼型,后者是8配位的双帽三棱柱几何构型。二维面状超分子结构的形成方式也明显不同,区别在于配合物1和2通过微弱的π-π堆积作用形成。配合物4和5是同构的,结构中引入了硝酸根离子较为有趣,通过C―H···F氢键和π-π堆积作...     

复合物Mg+-NCSCH3光诱导反应

观察了复合物Mg⁺-NCSCH₃在230~440 nm范围的光解离光谱. 在此波段内的复合物光诱导产物的质谱显示, 存在着非反应猝灭产物Mg⁺和反应产物Mg⁺NC、Mg⁺NCS. 反应产物来源于S－C化学键的断裂. 复合物的光解离光谱由两个对应于原子Mg⁺(3²P←3²S)跃迁的宽峰构成. 由量化计算中的CIS方法所获得的吸收谱理论值与实验值吻合较好.     

The influence of hyperfine structure and isotope shift on the detection of Rb by 2f-wavelength modulation diode laser absorption spectrometry-experimental verification of simulations

This work presents an experimental verification of a previously developed methodology for simulation of the 2f-wavelength modulation diode laser absorption spectrometry technique (2f-WM-DLAS) when the influence of hyperfine structure, isotope shift and collisional broadening and shift of an atomic transition is taken into account [J. Gustafsson, D. Rojas and O. Axner, Spectrochim. Acta, 52B, 1937–1953 (1997)]. The pilot element in the simulations was Rb, detected at the 780 nm 5s ²S_1/2−5p ²P_3/2 transition, in low-pressure cells and atmospheric-pressure reservoirs (e.g. graphite furnaces). This experimental investigation verifies that the simulations are able to predict, with good accuracy, experimental 2f-WM signals from Rb atoms under both low-pressure, room-temperature conditions and atmospheric-pressure, high-temperature conditions. This implies that the previously published simulation methodology can be used for predicting and optimizing 2f-WM signal strengths and shapes from Rb atoms (and thereby presumably also from other atoms) under a variety of pressure and temperature conditions.     

All electron ab initio investigations of the electronic states of the MoN molecule

The low lying electronic states of the molecule MoN were investigated by performing all electron ab initio multi-configuration self-consistent-field (CASSCF) calculations. The relativistic corrections for the one electron Darwin contact term and the relativistic mass-velocity correction were determined in perturbation calculations. The electronic ground state is confirmed as being ⁴∑⁻. The chemical bond of MoN has a triple bond character because of the approximately fully occupied delocalized bonding π and σ orbitals. The spectroscopic constants for the ground state and ten excited states were derived. The excited doublet states ²∑⁻, ²Γ, ²Δ, and ²∑⁺ are found to be lower lying than the ⁴Π state that was investigated experimentally. Elaborate multi-configuration configuration-interaction (MRCI) calculations were carried out for the states ⁴∑⁻ and ⁴∏ using various basis sets. The spectroscopic constants for the ⁴∑⁻ ground state were determined as r_e=1.636 Å and ω_e=1109 cm⁻¹, and for the ⁴∏ state as r_e=1.662 Å and ω_e=941 cm⁻¹. The values for the ground state are in excellent agreement with available experimental data. The MoN molecule is polar with a charge transfer from Mo to N. The dipole moment was determined as 2.11 D in the ⁴∑⁻ state and as 4.60 D in the ⁴∏ state. These values agree well with the revised experimental values determined from molecular Stark spectroscopic measurements. The dissociation energy, D_e, is determined as 5.17 eV, and D₀ as 5.10 eV.     

The discrimination between triplet state and radical cation in the pulse radiolysis of bithiophene in CCl4

The triplet state (³2T) and the radical cation (2T⁺√) of 2,2′-bithiophene (2T) are characterized by pulse radiolysis in CCl₄. Two main absorption bands at 360 and 420 nm are respectively attributed to ³2T* and to 2T⁺√. The triplet, induced in an excited state through a Förster mechanism, undergoes a conformational rearrangement (k₆=(6.8±0.9)×10⁶ s⁻¹). The radical cation is produced both through a resonance charge transfer and a second diffusional process; the two oxidizing species are respectively CCl₄⁺√ and (CCl⁺₃Cl⁻)_solv through the mediation of a singlet excited state, ¹2T*.     

193 nm Laser dissociation of CS2: prompt emission from CS and internal energy distribution of CS(XΣ)

Single and multiple photon processes are identified in the 193 nm excimer laser photolysis of CS₂. CS(X¹Σ⁺, υ = 1 to 5, J = 5 to 45) is observed by dye laser induced fluorescence of the A¹Π ↔ ; X¹Σ⁺ transition, following the single photon 193 nm photolysis of CS₂. Multiple photon 193 nm generation of CS fragment emission from 620 to 170 nm is also reported. A partial assignment of the emission spectrum identifies fluorescence from the CS A′¹Σ⁺ and A¹Π states.     

Laser induced photodissociation spectroscopy: Br2

The continuous absorption spectrum of molecular bromine has been examined using laser induced photodissociation spectroscopy. In this technique, Br₂ molecules are photolyzed using a flashlamp-pumped dye laser; the atomic products of the dissociation are then monitored by time-resolved resonance absorption spectroscopy in the vacuum ultraviolet. The relative absorptivities for the transitions B³Π_o⁺u ← X¹Σ⁺_g and ¹Π_1u ← X¹Σ⁺_g have been obtained at 18350, 21010 and 22125 cm⁻¹.     

Al6ONa2组装Zintl相晶体的理论研究

结合遗传算法和从头算方法确定了Al₆ONa₂的低能异构体. 揭示了以非金属为中心的Al-Na团簇的幻数行为. 金属团簇离域的凝胶轨道和非金属原子的价轨道作用形成定域在O原子上的成键轨道和离域在整个团簇上的反键轨道, 26个价电子形成s ²p ⁶S ²P ⁶D ¹⁰的闭合壳层强幻数电子结构. Al₆O ^2-与Na ⁺通过离子键结合, Al₆O ^2-的电子结构符合Wade-Mingos规则. 基于超原子阴离子Al₆O ^2-具有较强的热稳定性和化学惰性, 组装了具有Pn \bar{3} m和Fd \bar{3} m空间群的AB₂型晶体结构, Al₆ONa₂团簇的结合能为-23.44 eV, 组装结构中团簇单元间的相互作用能分别为-1.19和-1.53 eV. 晶体结构的电子结构分析表明, 2种组装晶体均为宽带隙半导体. 声子色散曲线和弹性常数的计算表明组装晶体具有良好的动力学稳定性.     

氧硫化碳在230 nm光激发下的S(~3P)解离通道

在230nm激光激发下,氧硫化碳(OCS)分子迅速解离生成振动基态但高转动激发的CO(X~1∑_g~+,v=0,J=42-69)碎片,并通过共振增强多光子电离技术实现其离子化。通过检测处于J=56-69转动激发态CO碎片的离子速度聚焦影像,我们获得了各转动态CO碎片的速度分布和空间角度分布,其中包含了S(1D)+CO的单重态和S(~3P_J)+CO三重态解离通道的贡献。不同的转动态CO碎片对应三重态产物通道的量子产率略有不同,经加权平均我们得到230 nm附近光解OCS分子中S(3P)解离通道的量子产率为4.16%。结合高精度量化计算的OCS分子势能面和吸收截面的信息,我们获得了OCS光解的三重态解离机理,即基态OCS(X~1A')分子吸收一个光子激发到弯曲的A~1A'态之后,通过内转换跃迁回弯曲构型的基电子态,随后在C-S键断裂过程中与2~3A"(c~3A")态强烈耦合并沿后者势能面绝热解离。     

芘基查尔酮的合成及三阶非线性光学性质

合成了一种新的具有潜在应用价值的非线性光学(NLO)有机材料1-(芘-1-基)-3-(4-二甲氨基苯基)丙烯酮(PMAK),并通过 NMR、IR、MS和元素分析等技术手段进行了表征。 采用溶液Nd:YAG激光技术测定了PMAK的三阶非线性光学性质并确定了相关参数。 纳秒实验结果:折射率n₂=-3.5×10^-17 m²/W,吸收系数β=7.0×10^-10 m/W,极化率χ⁽³⁾=2.54×10^-11 esu,分子超极化率γ=3.44×10^-30 esu;皮秒实验结果:n₂=-2.8×10^-18 m²/W,β=8.3×10^-11 m/W,χ⁽³⁾=2.49×10^-12 esu,γ=3.33×10^-31 esu。     

A quantum mechanical analysis on the selective production of the oxygen atom fine-structure states along asymmetric resonances in OH predissociation

Predissociation of the A ²Σ⁺ state is treated by an exact theory employing two frame transformation matrices, each of which connects the atomic term limits (O(³P) and O(¹D)) to the correlating adiabatic Born—Oppenheimer states. Resonances corresponding to the higher (v 7) rovibrational levels of the A ²Σ⁺ state are predicted to have asymmetric (Fano-type) profiles. The branching ratios of O(³P_j, J = 0, 1, 2) are shown to be influenced by nonadiabatic interactions in the Franck—Condon region between the A ²Σ⁺ and dissociative ⁴Σ⁻, ²Σ⁻ and ⁴Π states. The branching ratios show a strong variation along asymmetric resonances, while remaining energy independent along Lorentzian resonances.     

溴代烷烃与活性氮的反应发光研究

在流动余辉装置上, 利用N₂空心阴极放电制备活性氮, 研究了活性氮与溴代烷烃(CHBr₃、CH₂Br₂、C₂H₅Br、C₄H₉Br) 反应的化学发光.上述所有反应中, 在550～750 nm波段均观察到了较强的NBr (b¹Σ+→X³Σ^-)跃迁发射谱. 同时在活性氮与CHBr₃和CH₂Br₂的反应中, 在流动管下游还观察到了CN (A²π, B²π→X²Σ⁺)的发射谱. 验证性的实验表明, 激发态NBr (b¹Σ⁺)是由二步过程形成: N(⁴S)与溴代烷烃反应生成NBr (X³Σ^-), 再通过N₂ (A ³Σ_u⁺)分子能量转移到激发态NBr (b¹Σ⁺); 而激发态的CN是通过N(⁴S) + CBr→CN(A, B) + Br过程形成的.     

气相中CrO2+和H2反应的理论研究

用密度泛函UB3LYP/6-311++G(3df, 3pdpd)//6-311G(2dd, p)方法计算研究了在二重态和四重态两个势能面上的气相反应：CrO₂⁺ + H₂→CrO⁺+ H₂O. 对影响反应机理和反应速率的势能面交叉进行了讨论, 并运用Hammond 假设和Yoshizawa 等的内禀反应坐标(IRC)单点垂直激发计算的方法找出了势能面交叉点(crossing point (CP)). 运用碎片分子轨道(fragment molecular orbital(FMO))理论, 对初始复合物2IM1和4IM1的轨道相关进行了分析, 解释了CrO₂⁺活化H—H σ键及H₂迁移的机理.     

Kinetic and mechanistic study of the chlorpromazine-hydrogen peroxide reaction for the catalytic spectrophotometric determination of iodide

Extensive kinetic studies were performed to investigate the mechanism of the chlorpromazine (CP)-hydrogen peroxide reaction utilized in the catalytic determination of iodide. This reaction proceeds by two independent, parallel reactions, one through the formation of a red free radical, another directly to form the colorless product. The red color formation is catalyzed by traces of iodide. The color formation reaction was followed by measuring the increase in absorbance at 525 nm and its kinetic investigations were carried out by the initial rate method. The reaction rate curves for colorless sulfoxide formation were obtained by following the increase in absorbance at 335 nm, and the analysis was carried out by the integration method. The disappearance rate of CP is given by -d[CP]dt = k₃[I⁻[H₂O₂][H⁺] + k₆[CP][H₂O₂][H⁺] + k₉[CP][H₂O₂][H⁺] + k₁₀[CP][H₂O₂], where the first and second terms correspond to the chromogenic reaction and the third and fourth to colorless sulfoxide formation. Mechanisms consistent with each term were proposed and analytical implications of the kinetic studies are discussed.