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Extreme high rotational excitation of ClO ClO的极高旋转激励
Pub Date : 2001-01-01 DOI: 10.1039/B108052K
R. Aures, K. Gericke, M. Kawasaki, C. Maul, Y. Nakano, G. Trott-Kriegeskorte, Zhenya Wang
We observed the population of extremely high non-thermal rotational states of ClO (J max  = 130.5) upon photodissociation of Cl 2 O. State-resolved and isotope-specific detection of nascent ClO is performed by observing single colour (2 + 1) resonance enhanced multiphoton ionisation (REMPI) spectra following excitation in the wavelength range from 336 to 344 nm. The REMPI spectrum is assigned to the ClO(C 2 Σ – , v′ = 0 ← X 2 Π Ω , v = 0) transition. The non-thermal population of rotational states is highly inverted, peaking at J = 107.5. The photodissociation of Cl 2 O is a classical example for the pure impulsive model, as a consequence of the Cl 2 O mass distribution and a weak dependence of the upper potential energy surface on the bond angle. Cl 2 O can thus be used as clean source for laboratory generation of highly excited ClO molecules with a defined non-thermal rotational population. In kinetic studies using ClO from Cl 2 O as precursor the high rotational excitation needs to be considered carefully.
我们观察到在cl2o光解作用下,ClO具有极高的非热旋转态(jmax = 130.5)。在336 ~ 344 nm的波长范围内,通过观察激发后的单色(2 + 1)共振增强多光子电离(REMPI)光谱,对新生ClO进行了状态分辨和同位素特异性检测。REMPI光谱归属于ClO(c2 Σ -, v ' = 0←x2 Π Ω, v = 0)跃迁。转动态的非热居群高度反转,在J = 107.5处达到峰值。由于二氧化氯的质量分布和上势能面对键角的依赖性较弱,二氧化氯的光解是纯脉冲模型的经典例子。因此,cl2o可以作为实验室生成具有确定的非热转动居群的高激发ClO分子的清洁来源。在以cl2o中的ClO为前体的动力学研究中,需要仔细考虑高旋转激发。
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引用次数: 1
On the dimers of the VIB group: a new NIR electronic state of Mo2 VIB基团二聚体:Mo2的新近红外电子态
Pub Date : 2001-01-01 DOI: 10.1039/B104063B
D. Kraus, M. Lorenz, V. Bondybey
Laser vaporized Mo 2 is trapped in solid neon at 7 K and investigated by optical spectroscopy using a Fourier transform spectrometer. Besides the well known A 1  ← X 1 and a( 3 Λ) → X 1 transitions, a new NIR transition, denoted as a 3  → X 1 based on DFT calculations, is detected with the help of optical absorption and laser induced fluorescence spectroscopy. The visible A 1  ← X 1 transition of the mixed CrMo is observed for the first time in the gas phase using cavity ringdown absorption spectroscopy.
激光汽化的二氧化钼在7 K时被捕获在固体氖中,并用傅里叶变换光谱仪对其进行了光谱学研究。除了已知的a1←x1和A (3 Λ)→x1跃迁外,利用光学吸收和激光诱导荧光光谱检测到一种新的近红外跃迁,基于DFT计算表示为3→x1。利用腔衰荡吸收光谱首次在气相中观察到混合CrMo的可见a1←x1跃迁。
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引用次数: 21
Ab initio study of ammonium perchlorate combustion initiation processes: unimolecular decomposition of perchloric acid and the related OH + ClO3 reaction 高氯酸铵燃烧起爆过程的从头计算研究:高氯酸的单分子分解及相关的OH + ClO3反应
Pub Date : 2001-01-01 DOI: 10.1039/B109523B
R. Zhu, M. Lin
The unimolecular decomposition of HClO 4 has been investigated at the G2M//B3LYP/6-311+G(3df, 2p) level of theory. Above 500 K, the decomposition process was found to depend strongly on pressure below 200 atm. The rate constants at the high- and low-pressure limits were predicted to be k 1 ∞  = 1.5 × 10 17 exp(–26500/T) s –1 and k 1 0  = 3.39 × 10 30 T –10.9 exp(–29430/T) cm 3  molecule –1  s –1 , respectively. Under the atmospheric-pressure condition, the predicted first-order rate coefficient for the temperature range 300–3000 K, k 1  = 5.0 × 10 51 T –11.64 exp(–30700/T) s –1 , agrees reasonably with experimental data obtained at 550–750 K by different experimental groups. We have also calculated the rate constants for the bimolecular reaction of OH with ClO 3 producing HClO 4 by association/stabilization and HO 2  + ClO 2 by association/fragmentation. At the high-pressure limit, the rate constants can be given as:k –1  = 3.2 × 10 –10 T 0.07 exp(–25/T) cm 3  molecule –1  s –1 and k 2  = 2.1 × 10 –10 T 0.09 exp(–18/T) cm 3  molecule – 1 s –1 , respectively, for the temperature range 300–3000 K. Under the atmospheric pressure condition, the OH + ClO 3 reaction produces predominately the HO 2  + ClO 2 products.
在G2M//B3LYP/6-311+G(3df, 2p)理论水平上研究了hclo4的单分子分解。在500k以上,发现分解过程强烈依赖于200atm以下的压力。在高压和低压极限下的速率常数分别为k1∞= 1.5 × 10 17 exp(- 26500/T) s - 1和k10 0 = 3.39 × 10 30 T - 10.9 exp(- 29430/T) cm 3分子- 1 s - 1。在常压条件下,在300 ~ 3000 K温度范围内的一阶速率系数K 1 = 5.0 × 10 51 T -11.64 exp(-30700 /T) s -1,与不同实验组在550 ~ 750 K下得到的实验数据吻合较好。我们还计算了OH与clo3的双分子反应通过缔合/稳定生成hclo4和通过缔合/碎裂生成ho2 + clo2的速率常数。在高压极限下,在300-3000 k范围内,反应速率常数分别为:k - 1 = 3.2 × 10 - 10 T 0.07 exp(- 25/T) cm 3分子- 1 s - 1和k - 2 = 2.1 × 10 - 10 T 0.09 exp(- 18/T) cm 3分子- 1 s - 1。常压条件下,OH + clo3反应主要生成ho2 + clo2产物。
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引用次数: 10
Molecules as products; the good, the bad and the eccentric 分子作为产物;好的,坏的和古怪的
Pub Date : 2001-01-01 DOI: 10.1039/B108077F
A. J. McCaffery, R. Marsh
Guided by experimental findings, we develop a nuclear dynamical theory of molecular collisions that accounts quantitatively for product distributions in a wide range of inelastic and reactive processes. Two simple equations are sufficient for this purpose. The first represents the principal mechanism by which linear momentum of relative motion is converted to angular momentum via a torque arm of molecular dimension. The second is a statement of energy conservation and this (together with the requirement that products be formed in well-defined quantum states) constitutes the boundary condition within which the mechanism must operate. Boundary conditions vary widely with system and with process and give great variety to the final rotational state distributions. Both equations may be represented in velocity–angular momentum diagrams from which the origins of the characteristic features of many processes, particularly their product rotational state distributions, may be identified. Quantitative calculations reproduce experimental data over a wide range of inelastic and reactive collisions and for molecules in low-lying or highly excited states. Input data in the calculations consists of little more than atomic mass, bond length and velocity distributions (and reaction enthalpy for reactive processes). Collisional behaviour in this model is characteristic of an individual molecule and we outline the beginnings of a classification scheme that categorises molecules as good (efficient) or bad (inefficient) in terms of their ability to convert linear-to-angular momentum within the constraints appropriate to system and process. Molecules such as the hydrides of heavier elements fall into a category we term ‘eccentric’ as a result of unusual (but predictable) collisional properties.
在实验结果的指导下,我们发展了分子碰撞的核动力理论,定量地解释了大范围非弹性和反应过程中的产物分布。两个简单的方程就足够了。第一个是通过分子尺度的力矩臂将相对运动的线性动量转换为角动量的主要机理。第二个是能量守恒的陈述,这(连同产物必须在定义良好的量子态中形成的要求)构成了该机制必须运行的边界条件。边界条件随系统和过程的不同而变化很大,使最终的旋转态分布变化很大。这两个方程都可以用速度-角动量图来表示,从中可以确定许多过程的特征特征的起源,特别是它们的乘积旋转状态分布。定量计算再现了大范围的非弹性碰撞和反应性碰撞的实验数据,以及低空或高激发态的分子。计算中的输入数据仅包括原子质量、键长和速度分布(以及反应过程的反应焓)。该模型中的碰撞行为是单个分子的特征,我们概述了分类方案的开始,该方案根据分子在适当的系统和过程约束下将线性动量转换为角动量的能力,将分子分类为好(有效)或坏(低效)。分子,如重元素的氢化物,由于其不寻常的(但可预测的)碰撞特性,我们称之为“偏心”。
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引用次数: 1
Time-lapse potentiometric imaging of active filiform corrosion using a scanning Kelvin probe technique 利用扫描开尔文探针技术对活性丝状腐蚀进行延时电位成像
Pub Date : 2001-01-01 DOI: 10.1039/B100835H
Geraint Williams, H. McMurray, D. Hayman, P. Morgan
The kinetics and mechanism of filiform corrosion occurring on polymer coated AA2024-T3 aluminium alloy are investigated using a scanning Kelvin probe technique (SKPT). Repeated scanning by SKPT is used to generate a time-lapse animation showing the dynamic evolution of localised free corrosion potential (E corr ) patterns. E corr values in the head region of propagating filaments are up to 150 mV lower that the intact polymer coated surface, indicating local depassivation. However, E corr values in the filament tail are ca. 100 mV higher than background, indicating superpassivation. Spatial analysis of instantaneous E corr distributions indicates that anodic metal dissolution is concentrated at the leading edge, and cathodic oxygen reduction at the trailing edge, of active filament heads. Temporal analysis of time-dependent E corr distributions shows that filaments propagate at a constant speed and do not intersect.
采用扫描开尔文探针技术(SKPT)研究了聚合物包覆AA2024-T3铝合金的丝状腐蚀动力学和机理。通过SKPT的重复扫描,可以生成延时动画,显示局部自由腐蚀电位(E - corr)模式的动态演变。与完整的聚合物包覆表面相比,扩展细丝头部区域的E - corr值降低了150 mV,表明局部钝化。然而,灯丝尾部的ecorr值比背景高约100 mV,表明过度钝化。瞬时E - corr分布的空间分析表明,活性灯丝头的阳极金属溶解集中在前缘,阴极氧还原集中在尾缘。时间相关系数分布的时间分析表明,细丝以恒定速度传播,不相交。
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引用次数: 11
Entrapment and catalytic activity of gold nanoparticles in amine-functionalized MCM-41 matrices synthesized by spontaneous reduction of aqueous chloroaurate ions 金纳米粒子在氯金酸盐离子自发还原合成的胺功能化MCM-41基质中的包裹和催化活性
Pub Date : 2001-01-01 DOI: 10.1039/B101056P
Priyabrata Mukherjee, C. Patra, R. Kumar, M. Sastry
There is tremendous current interest in the generation of nano-hybrid materials using silicate mesoporous materials. We describe herein a new process for the synthesis of gold nanoparticle–amine functionalized MCM-41 hybrid materials by the spontaneous reduction of chloroaurate ions within the silicate matrix. The gold nanoparticles thus formed are bound to the pores of the MCM-41 framework by amine functional groups and show excellent catalytic activity in hydrogenation reactions.
目前人们对利用硅酸盐介孔材料制备纳米杂化材料非常感兴趣。本文介绍了一种在硅酸盐基质中自发还原氯金酸盐离子合成金纳米粒子-胺功能化MCM-41杂化材料的新工艺。由此形成的金纳米颗粒通过胺官能团与MCM-41骨架的孔结合,在加氢反应中表现出优异的催化活性。
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引用次数: 23
Surface enhanced Raman scattering from bare cobalt electrode surfaces 裸钴电极表面增强的拉曼散射
Pub Date : 2001-01-01 DOI: 10.1039/B105667K
D. Wu, Yong Xie, B. Ren, J. W. Yan, B. Mao, Z. Tian
Surface enhanced Raman spectra (SERS) of adsorbed species from a bare cobalt (Co) bulk electrode were observed for the first time with confocal Raman microscopy. A combined AFM, Raman and electrochemical study shows that a proper roughening procedure is vitally important for obtaining good-quality surface Raman spectra from the Co electrode. The surface enhancement factor ranges from 2 to 3 orders of magnitude, depending critically on the surface roughening procedure. The present study provides a bright prospect for the wide investigation of systems of practical application.
用共聚焦拉曼显微镜首次观察了裸钴(Co)体电极吸附物质的表面增强拉曼光谱(SERS)。原子力显微镜、拉曼光谱和电化学的综合研究表明,适当的粗化工艺对于获得高质量的钴电极表面拉曼光谱至关重要。表面增强系数范围从2到3个数量级,主要取决于表面粗化程序。本研究为实际应用系统的广泛研究提供了广阔的前景。
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引用次数: 15
Non-photochemical spectral hole-burning in the 2E←4A2 transition of crystalline NaMgAl(oxalate)3·9H2O∶Cr(III) NaMgAl(草酸盐)3·9H2O∶Cr(III)晶体2E←4A2跃迁的非光化学光谱烧孔
Pub Date : 2001-01-01 DOI: 10.1039/B110096C
M. L. Lewis, H. Riesen
Non-photochemical spectral hole-burning in the 2 E← 4 A 2 transition of crystalline NaMgAl(oxalate) 3 ·9H 2 O∶Cr(III) and its temperature dependence is reported and a hole-burning mechanism is proposed. This is the first report of non-photochemical hole-burning in the 2 E← 4 A 2 transition of chromium(III) in a crystal.
报道了晶体NaMgAl(草酸盐)3·9 h2o∶Cr(III)在2 E←4 a2跃迁过程中的非光化学光谱烧洞及其温度依赖性,并提出了烧洞机理。本文首次报道了晶体中铬(III)在2 E←4 a2跃迁过程中的非光化学烧孔现象。
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引用次数: 0
Structure and dynamics of the Mu adduct of diketene 二烯烯Mu加合物的结构与动力学
Pub Date : 2001-01-01 DOI: 10.1039/B110704F
I. McKenzie, B. Addison-Jones, J. Brodovitch, K. Ghandi, P. W. Percival
The radical formed by muonium addition to diketene has been studied by transverse field muon spin rotation (TF-µSR) and muon avoided level-crossing resonance (µALCR). The TF-µSR spectrum shows that muonium adds to only one site in diketene, and it is clear from the µALCR spectrum that the radical product contains two inequivalent sets of protons. The muon and proton hyperfine coupling constants (hfcs) were determined at several temperatures between 280 and 362 K. The muon hfc falls with increasing temperature, one proton hfc increases, and the other remains constant. The magnitude and temperature dependence of the hfcs support assignment of the 4-muonomethyl-oxetan-2-on-4-yl radical. Density functional calculations were performed to model the temperature dependence of the hfcs. The results are consistent with a preferred conformation of the muoniated methyl group in which the C–Mu bond eclipses the orbital containing the unpaired electron.
用横向场介子自旋(TF-µSR)和介子避免平交共振(µALCR)研究了介子加入双烯酮形成的自由基。TF-µSR光谱显示,介子元素只加入到双烯酮的一个位点上,而µALCR光谱则清楚地表明,自由基产物包含两组不相等的质子。在280 ~ 362 K的温度范围内测定了介子和质子的超精细耦合常数。μ子的hfc随温度升高而下降,一个质子的hfc增加,而另一个保持不变。4-甲基氧乙基-2-对-4-基自由基的氢氟碳化合物支持配位的大小和温度依赖性。密度泛函计算模拟了氢氟碳化合物的温度依赖性。结果与甲基化的优先构象一致,其中C-Mu键使含有未配对电子的轨道黯然失色。
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引用次数: 1
Onset temperature of slow dynamics in glass forming liquids 玻璃成型液体的慢动力学起始温度
Pub Date : 2000-12-05 DOI: 10.1039/B008749L
S. Sastry
The behaviour of a model glass forming liquid is analyzed for a range of densities, with a focus on the temperature interval where the liquid begins to display non-Arrhenius temperature dependence on relaxation γ. Through analyzing the dynamics along with the properties of local potential energy minima sampled by the liquid, a crossover or onset temperature Ts is identified, below which the liquid manifests slow dynamics, and a change in the character of typical local potential energy minima
在密度范围内分析了模型玻璃形成液体的行为,重点关注液体开始显示非阿雷尼乌斯温度依赖于弛豫γ的温度区间。通过分析液体取样的局部势能极小值的动力学特性,确定了一个交叉或起始温度Ts,在此温度以下,液体表现为缓慢的动力学,并改变了典型的局部势能极小值的特征
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引用次数: 28
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PhysChemComm
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