一种疑似合成钻石的天然钻石光谱学特征

该研究团队在近期日常检测中发现一粒疑似合成钻石的天然钻石。该样品的质量为0.029 5 g(0.14 ct),尺寸为3.32 mm×3.33 mm×2.08 mm,颜色级别为H,净度级别SI₁,在正交偏光镜下具有异常消光现象。该样品在短波紫外灯下具有强的绿黄色荧光,并伴有强烈的绿黄色磷光现象,磷光持续时间50 s以上;傅里叶变换红外光谱仪测试确认该样品为Ⅱa型,在1 400～400 cm^-1无明显吸收峰,在1 970～2 500 cm^-1处具有由C—C晶格振动所引起的吸收峰;紫外可见光谱仪测试未检测到415 nm吸收峰,显示270 nm吸收峰。上述特征疑似HPHT合成钻石。为确认该样品的成因,又对其做了部分光谱测试,采用De Beers研制的Diamond-view^TM测试样品的发光图像,该样品的发光图像呈蜥蜴皮状、蜂窝状;采用常温光致发光光谱仪测试,选用405 nm光源激发时,可见415、 428和450 nm特征峰;选用365 nm光源激发时,可见415、 428和450 nm特征峰以及氮空位中...     

离子碰撞过程中电荷转移的理论研究

用经典轨道蒙托卡罗(CTMC)方法计算离子与氢原子碰撞过程电荷转移截面,并计算俘获电子的n(n为主量子数)壳层分布。对于多电荷离子的碰撞过程,利用约化变量得到了截面的q标度规律。计算结果与实验测量符合得很好。     

电场变化对有机磷光器件中激子形成影响的研究

激子形成区域随电场变化的移动会使得有机电致发光器件(OLEDs)的效率和色度发生改变,从而影响器件的性能。文章首先制备了两种OLED器件,器件1为ITO/PEDOT∶PSS/PVK∶Ir(ppy)₃∶DCJTB (100∶2∶1 wt)/BCP(10 nm)/Alq₃(15 nm)/Al,器件2为ITO/PEDOT∶PSS/PVK∶Ir(ppy)₃(100∶2 wt)/BCP(10 nm)/Alq₃(15 nm)/Al,研究了电场强度对单层多掺杂结构器件激子形成的影响。实验发现在多掺杂发光层中,随着电压的增加,Ir(ppy)₃,PVK和DCJTB的发光均增强,PVK和DCJTB发光增强更快。对其发光机制进行分析,认为较高电场下,载流子获得较高能量,更容易形成高能量激子,产生宽禁带材料PVK的发光;另一方面,从能级结构分析DCJTB的带隙较窄, 俘获更多的载流子发光更强。同时,在器件的电致发光(EL)光谱发现在460 nm处一新的发射峰, 发光随着电压的增大相对减弱。为了研究460 nm发光的来源,制备了器件：ITO/PEDOT∶PSS/PVK∶BCP∶Ir(ppy)₃(x∶y∶2 wt)/Alq₃(15 nm)/Al, 改变x, y的比值研究发现,460 nm处的发光依然存在,推测此发光峰应与PVK及BCP之间有关。     

原子轨道方法研究等离子体中He2+ -H碰撞的电荷转移过程

应用双中心的原子轨道强耦合方法研究了理想等离子体环境中的He2 -H碰撞的电荷转移过程,计算了不同德拜半径下随入射粒子能量变化的单电子俘获过程的总截面及态选择截面.计算结果表明:随着德拜半径的变化,等离子体中原子的电子波函数及其能量本征值发生了显著的变化;而且,随着屏蔽效应的增加,发生电荷转移过程的反应通道的个数逐渐减少,因此导致总的单电子俘获截面也逐渐减小.     

大柴旦卤水中硼的提取

大柴旦盐湖含硼,卤水生产硼酸一般有两种工艺,一是传统的酸法提硼工艺,二是离子交换(树脂)提硼工艺,为减少硼在固相中的夹带损失,进行离子交换法从原卤水中和分离NaCl后溶液中提取硼的试验,硼的回收率达到了80%以上.     

探测到τ子型中微子存在的直接证据

 众所周知,按照粒子物理学标准模型和理论,物质应该由１２种基本粒子所构成,它们包括６种夸克和６种轻子。夸克包括下、上、奇异、粲、底、顶６种。轻子包括电子、电子中微子、μ子、μ子中微子、τ子和τ子中微子。至１９９５年,科学家通过多种实验手段已先后陆续探测到了除τ子中微子以外的１１种基本粒子,２０００年又发现了τ子中微子存在的直接证据。１９７８年,美国斯坦福大学物理学家马丁·佩尔从实验上发现了τ轻子,表明了τ子中微子的存在,从而荣获１９９５年诺贝尔物理学奖。但由于τ子中微子不带电,又几乎不与周围物质相互作用,所以科学家很难直接探测到它。     

银溶胶中电荷转移诱导的表面增强拉曼光谱研究

在银溶胶中加入具有双官能团的对氨基苯甲酸分子,银纳米粒子可以通过耦联分子PABA的作用相连,在两个或几个银纳米粒子间形成亚纳米级的间隙,处于间隙中的耦联分子的拉曼信号被极大的增强,尤其是b2振动模式得到了极大增强,这可能是由于银纳米粒子间耦联分子的隧道电荷转移现象引起的.     

荧光法测定银杏叶中不同形态的硼

优化了分子荧光法测定硼-变色酸络合物的实验条件,提出了一种新的形态分析方法-连续浸提法.方法检出限为3.28μg/L,相对标准偏差为3.91%.该方法应用于银杏叶中不同形态硼含量的测定,结果满意.     

基于表面增强拉曼光谱的染料敏化太阳能电池中高压对电荷转移的影响研究

界面电荷转移(CT)在提高染料敏化太阳能电池(DSSCs)的光电转换效率中起重要作用,但一直未被充分探索。在这里,构建了TiO₂@N719@Ag DSSCs体系,并通过表面增强拉曼散射(SERS)光谱监测了CT过程。同时,作为最常见的外部刺激之一,高压会增加TiO₂ NPs的自由载流子密度并导致带隙变窄。在高压SERS实验中,观察到N719染料在TiO₂@N719@Ag体系中显着增强至压力达到2.48 GPa,这与电荷转移度(ρ_CT)的变化趋势一致。表明带隙变化会强烈影响CT过程,进一步影响SERS信号强度(或ρ_CT),从而增加DSSCs的CT概率。最后,为了更清楚地观察DSSCs的CT过程,提出了描述CT机制的模型。SERS光谱有望成为探索DSSCs设备中界面CT行为的一种有前途的技术,这可能会进一步拓宽提高电池效率的思路。     

ICP-AES法测定快干胶中硼的研究

本文探讨了ＩＣＰ－ＡＥＳ法测定快干胶中硼的方法,选择了合适的测定条件,并有效地克服了测定过程中的“记忆效应”,以石英氧瓶燃烧法分解快干胶试样,有效地避免了硼的污染和逸失。该法简便,快速。实际样品测定的相对标准偏差为１０％,回收率为９１％￣９６％。     

共轭低聚物中光生分子间电荷转移态的第一性原理研究

We perform density functional theory calculations to investigate the polaron pair (charge transfer state) photo-generation in donor-acceptor oligomer methyl-capped (4,7-benzo[2,1,3]thiadiazole-2,6-(4,4-bis (2-ethylhexyl)-4H-cyclopenta[1,2-b;3,4-b'']dithiophene-4,7-benzo[2,1,3]thiadiazole)(CPDTBT).Results show that effective photo-generation of charge transfer state can happen in CPDTBT dimer when the group 4,7-benzo[2,1,3]thiadiazole (BT) in one monomer deviates against the conjugated plane (onset torsion angle is about 20°).The lower excitation energy (530 nm) can only generate the intramolecular excitonic state,while the higher excitation energy (370 nm) can generate the intermolecular charge transfer state,in good agreement with the experiment.Moreover,the mechanism of charge separation in CPDTBT oligomers is discussed.     

Visualization of Metal-to-Ligand and Ligand-to-Ligand Charge Transfer in Metal-Ligand Complexes

利用三种方法可视化化了Ru(II) ammine的金属到配体的电荷转移. 首先原子分辨的态密度显示HOMO上的密度主要在Ru上,LUMO 上的态密度在ammine上,这说明Ru上激发的电子会转移到ammine配体上. 第二,电荷差异密度揭示了所有的空穴都在Ru上,所有的电子都在ammine上. 第三,跃迁密度矩阵揭示了Ru和ammine上的电子空穴对的相关性. 这三种方法也用来研究Os(bpy)₂(p0p)Cl的金属到配体的电荷转移和Alq3配体到配体的电荷转移.     

侧链结构对PPV/C_(60)组合体系的激发传递和电荷转移过程的影响

本文考察不同的侧链长度对聚对苯乙炔 (PPV)衍生物的光学性质等的影响 ,以及PPV/C60 的组合薄膜中的激发传递和电荷转移过程。结果表明随着连接在PPV的侧链长度的增长 ,其π π 跃迁带隙变窄 ,使得吸收和发射峰的位置逐渐红移 ;同时观测到PPV/C60 间存在着极有效的激发传递过程 ,从而使得PPV衍生物的荧光在很大程度上被C60 分子所猝灭 ;MD PPV/C60 组合膜中观测到了C-60 的吸收峰 ,这表明该体系存在着基态电荷转移过程 ,同时也表明PPV衍生物与C60 分子间的相互作用和PPV的侧链长短密切相关。     

电荷直接隧穿特征时间的计算模型

在分析硅基纳米存储器的势结构和价带混合效应对直接隧穿过程影响的基础上,采用顺序隧穿理论和巴丁传输哈密顿方法,发展了电子和空穴直接隧穿时间的计算模型.利用该模型数值计算了硅基纳米存储器的编程时间和保留时间,讨论了结构参数和外加偏压对器件存储性能的影响,指出需要设计新的器件结构模型来优化硅基纳米存储器的保留特性.     

Charge transfer from the ground state of muonic hydrogen to at room temperature

The present status of research of muon transfer from the ground state of muonic protium to ⁴He is reviewed. The analysis of a recent measurement in a triple gas mixture of H₂+⁴He+Ne at 15 bar and room temperature is presented and the result is compared to the existing experimental and theoretical rates. The average muon transfer rate from protium to ⁴He determined from all lifetime measurements is . Received: 22 January 1998 / Revised: 4 March 1998 / Accepted: 31 March 1998     

Microscopic Analysis of 5d States Splitting and Charge Transfer Energies Dependence on Interionic Distance in Alkaline Earth Fluorides Doped with Light Trivalent Lanthanides

A first principles fully relativistic analysis (K. Ogasawara et al., Phys. Rev. B 2001, 64, 115413) of the dependence of 5d orbitals splitting (10Dq) and charge transfer (CT) energies on interionic distance has been performed for light lanthanides (Ce³⁺, Pr³⁺, Nd³⁺) in CaF₂, SrF₂, BaF₂ crystals. The salient feature of the method is that four‐component molecular orbitals (MO) composed of atomic wave functions are used as the basis set. Without any fitting parameter, the power dependencies for 10Dq and linear dependencies for the CT energies on the distance between rare‐earth (RE) ions and ligands were obtained. A comparison with experimental values is discussed.     

Ba2MgGe2O7:Cr4+晶体中荷移激发态对g因子贡献的研究

文章建立了立方四面体3d2络合物g因子的完全高阶微扰公式.在这个公式中,除了与d-d跃迁光谱(晶场激发态)有关的晶场(CF)机制的贡献(包括近年发展的双旋-轨耦合参量模型)外,与电荷转移光谱(荷移激发态)有关的荷移(CT)机制的贡献也被考虑.将这个公式应用于Ba2MgGe2O7:Cr4 晶体平均g因子的计算,发现理论计算值与实验值很好的一致,同时,荷移机制对g移动△g(=g-2.002 3)的贡献△gCT在符号上与晶场机制的贡献△gCF相反,而在大小上约为晶场机制贡献的38%.因此,在对高价态过渡金属离子络合物的g因子计算时应考虑CF机制和CT机制的贡献.     

Charge transfer complex formation at the air-water interface “in situ” studied by means of UV-vis reflection spectroscopy

Positively ionized monolayers of a viologen derivative, namely 1,1′-dioctadecyl-4,4′-bipyridilium (C₁₈V²⁺), were prepared onto aqueous solutions of a tetracyanoquinodimethanide salt, , where the tetracyanoquinodimethanide anions are in a mixed valence state. UV-vis reflection spectroscopy has been used for proving in situ the incorporation of tetracyanoquinodimethanide anions into the viologen monolayer. The UV-vis spectra clearly show the presence of a band in the 550-850 nm region that is not visible in viologen monolayers fabricated onto a pure water subphase. Moreover, a charge-transfer interaction between the two molecules occurs at the air-water interface. A simultaneous quantitative analysis of the two active molecules in the UV-vis region has facilitated the investigation of the viologen tetracyanoquinodimethanide hybrid monolayers. An organization model at the air-water interface consistent with the reflection spectroscopy data has been proposed where a parallel arrangement of the viologen dications and anions is assumed. The ratio of the two materials in the monolayer was also determined and resulted to be , i.e. stoichiometry of charges. This ratio decreases after a noticeable kink in the π-A isotherm, and has been interpreted as a reorganization of the molecules in the monolayer leading to an ejection of some ions from the interface to the subphase, probably due to steric hindrance.     

Ab Initio Simulation of Charge Transfer at the Semiconductor Quantum Dot/TiO2 Interface in Quantum Dot‐Sensitized Solar Cells

Quantum dot‐sensitized solar cells (QDSSCs) have emerged as a promising solar architecture for next‐generation solar cells. The QDSSCs exhibit a remarkably fast electron transfer from the quantum dot (QD) donor to the TiO₂ acceptor with size quantization properties of QDs that allows for the modulation of band energies to control photoresponse and photoconversion efficiency of solar cells. To understand the mechanisms that underpin this rapid charge transfer, the electronic properties of CdSe and PbSe QDs with different sizes on the TiO₂ substrate are simulated using a rigorous ab initio density functional method. This method capitalizes on localized orbital basis set, which is computationally less intensive. Quite intriguingly, a remarkable set of electron bridging states between QDs and TiO₂ occurring via the strong bonding between the conduction bands of QDs and TiO₂ is revealed. Such bridging states account for the fast adiabatic charge transfer from the QD donor to the TiO₂ acceptor, and may be a general feature for strongly coupled donor/acceptor systems. All the QDs/TiO₂ systems exhibit type II band alignments, with conduction band offsets that increase with the decrease in QD size. This facilitates the charge transfer from QDs donors to TiO₂ acceptors and explains the dependence of the increased charge transfer rate with the decreased QD size.