有机反应的竞争性

有机反应的竞争性胡秀贞（南京师范大学化学系，２１００２４）竞争反应是有机化学中一个相当普遍的反应，所以我们研究有机反应机理时，必须具有有关这个反应的热力学和动力学的基本知识。大家知道热力学研究的一个重要内容是反应的起始状态和终止状态的能量变化，而动力...     

固态有机合成反应进展

以绿色合成为主题，综述了近期固相有机合成研究方面的一些新进展和典型反 应类型。由于固相反应的特征，多数固相有机反应表现出较溶液中更高的反应效率 和更好的选择性，并讨论了固态反应中的分子运动及其固态反应的因素。     

流化床煤气化炉内脱硫的研究 Ⅱ．脱硫剂焙烧反应动力学与脱硫反应动力学初步研究

钙质脱硫剂的焙烧反应是炉内脱硫的关键过程，本文研究了影响石灰石和白云石焙烧速率的因素。操作温度７５０℃以上时，焙烧速率很快。ＣＯ_２分压显著地影响焙烧过程，Ｐ_（ＣＯ）２高于平衡分压时，石灰几乎不分解。在本实验的粒度范围内，脱硫剂粒度对焙烧速率影响不大。采用未反应核收缩模型模拟焙烧过程的结果和实验结果基本一致。脱硫反应速率对气相Ｈ_２Ｓ浓度呈一级反应，操作温度特别在６００～７００℃的低温时显著地影响反应速率。     

Cl＋C_2H_6→HCl＋C_2H_5反应的准经典轨线研究

用三原子模型的准经典轨线方法研究了Cl与C2H6（v=0,j）的反应．计算结果表明，反应产物HCl的角度分布基本上为各向同性，其振转分布处于基态，与实验结果相一致,对反应轨线的研究表明，该反应为一直接反应．而且反应碰撞在低及高的碰撞参数下的机理不一样．在低碰撞参数下反应碰撞是直接完成的，产物HCl以向后散射为主，转动基本上是冷的，但比高碰撞参数下的热.在高的碰撞参数下则生成短寿命的碰撞复合物，产物HCl以向前散射为主，转动较冷．     

Cl+C2H6→HCl+C2H5反应的准经典轨线研究

用三原子模型的准经典轨线方法研究了Ｃｌ与Ｃ２Ｈ６（ｖ＝０，ｊ）的反应。计算结果表明，反应产物ＨＣｌ的角度分布基本上为各向同性，其振动分布处于基态，与实验结果相一致。对反应轨线的研究表明，该反应为一直接反应，而且反应碰撞在低及高的碰撞参数下的机理不一样，在低碰撞参数下反应碰撞是直接完成的，产物ＨＣｌ以向后散射为主，转动基本上是冷的，但比高碰撞参数下的热。在高的碰撞参数下则生成短寿命的碰撞复合物，产物     

天然气与硫酸盐热化学还原反应的模拟实验研究

为探讨天然气中高含量硫化氢形成的化学机制，利用高温高压反应装置，对天然气与固态硫酸钙反应体系进行了热模拟实验研究。使用气相色谱仪、微库仑仪、傅里叶变换红外光谱仪和X射线衍射仪对产物进行了分析，探讨了硫酸盐热化学还原反应的热力学特征，并进行了反应动力学研究。结果表明，高温下天然气与固态硫酸钙可以发生反应，产物主要为硫化氢、二氧化碳、碳酸钙、水和炭。热力学研究表明，天然气与固态硫酸钙的反应可行，升高温度对反应有利，同一温度下长链烷烃与固态硫酸钙发生反应的可能性要比短链烷烃大。根据动力学模型得到反应活化能为96.824kJ/mol。     

连续型季铵化反应的热动力学研究

应用热动力学法研究了Ｎ，Ｎ，Ｎ＇，Ｎ＇－四甲基－１，３－丙二胺与溴代正丁烷之间的连续季铵化反应，测定了２５．０、３５．０及４５．０℃和ＤＭＳＯ溶剂中该反应的速度常数，计算得到了其活化能及活化自由能，并讨论了温度和溶剂对反应动力学的影响。这些结果对认识季铵盐型离子聚合物的形成机理及反应条件的选择是十分重要的。     

微反应技术在均相反应中的应用

微反应技术是研究和开发新型化学过程的合适方法，能够精准控制混合时间和反应温度，获得高重复性结果，提高反应效率。微反应技术可应用于均相和多相反应体系，尤其适合处理高温、高压、强放热反应和易燃、易爆、有毒有害原料或中间体。本文总结了近年来微反应技术应用在不同均相反应中的研究，包括酸催化反应、光化学反应、不对称催化反应、其他液-液相及临界反应。提出了目前微反应技术在工程应用的主要问题和相关解决方案。模拟及研发新型微通道反应系统的关键在于统筹多尺度界面强化效果，结合其他使能技术避免潜在通道堵塞，通过破乳技术改善微界面反应条件，开发用于特殊复杂环境的新型复合通道材料，为今后微反应系统的工业化设计和优化提供参考。     

呋喃甲酸酯与三氯乙醛缩合反应研究

系统地研究了呋喃甲酸酯与三氯乙醛的缩合反应规律，提出了路易斯酸催化该反应的机制。当呋喃酸酯：无水三氯乙醛：三氯化铝（摩尔比）为２：１：１时，在６０～７０℃下反应６ｈ双分子缩合产物的收率为５３～７５％。     

炔烃的钛氢化反应及产物的立体结构

通过色谱跟踪对炔烃的钛氢化反应进行了研究，反应前期可得到高选择性高产率的顺式烯烃，反应后期可得到高选择性高产率的反式烯烃，控制反应烯烃，控制反应时间，用酮类淬息方法分别得到了一系列新的专一立体构型的烯丙醇衍生物。     

Applications of laser microprobe mass spectrometry in organic analysis

The ability to focus the laser accurately onto the sample with a small beam diameter (2.0–3.0 μm) enables laser mass spectrometry to be used as a microprobe. Results from a fully automated ion-mapping system for laser mass spectrometry are described. These results show that the spatial resolution of the laser microprobe is primarily limited by the diameter of the laser beam. Factors such as laser power density, laser focus, sample preparation, and chemical environment influence the reproducibility of laser mass spectra significantly. Calibration curves obtained in the analysis of mixtures of phenanthrolines demonstrate that laser mass spectrometry can be used to quantify organic components. Preliminary results on the detection of neutral molecules resulting from metastable decomposition in the flight tube are also presented.     

Laser Doppler methods in electrophoresis

Electrophoretic motion of particles, molecules, and biological cells can be readily measured by laser Doppler techniques. Small frequency shifts associated with the motion of the scatterers are detected by heterodyne detection of the scattered laser light. The principles of laser light scattering and heterodyne detection are reviewed. The central experimental problems associated with the application of electric fields to conducting solutions are considered in detail. Various types of laser Doppler spectrometers and electrophoresis chambers are compared both from fundamental physical points of view as well as in terms of resolving power of standard marker cells. As applications of the laser Doppler technique, measurements on proteins, virtues, nucleic acids, bioparticles and biological cells are reviewed.     

Multiphoton ionization of molecules: A comparison between femtosecond and nanosecond laser pulse ionization efficiency

Multiphoton ionization mass spectra of nonvolatile molecules laser desorbed into a supersonic beam are recorded. It is shown by indirect measurements that the laser desorption of neutrals is not mass limited, but lead to the formation of neutrals with intesities large enough for intense signals. To investigate the efficiency of the multiphoton ionization process with varying laser pulse durations, simultaneous laser pulses of 500 fs and 5 ns or 100 fs and 5 ns have been applied to the neutral beam. The energies of both femtosecond and nanosecond laser pulses are held in a comparable magnitude, and thus produce, in the resulting ion intensity, very large differences up to 4 orders of magnitude. For larger evaporated molecules (> 500 u) the ionization efficiency from nanosecond laser pulses drops significantly in comparison to femtosecond laser pulse excitation. A variety of possible reasons for the different ionization and dissociation behavior in femtosecond and nanosecond laser pulse excitations are discussed in this paper. It is rationalized that even with very short laser pulses and large molecules the “ladder switching model” for ionization and fragmentation is valid.     

硫化物矿物LA-ICP-MS激光剥蚀元素信号响应

采用193 nm ArF准分子激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)对5种天然硫化物矿物进行激光剥蚀分析, 基于不同硫化物矿物的剥蚀形貌特征和元素瞬时信号响应, 考察了硫化物矿物的元素分馏效应及激光频率、能量和激光斑径对硫化物矿物激光剥蚀行为的影响. 结果表明, 不同硫化物矿物的激光剥蚀形貌和元素分馏效应存在明显差异, 其中黄铁矿、辉钼矿和闪锌矿的剥蚀晕约为剥蚀斑径的10倍, 而黄铜矿和磁黄铁矿的剥蚀晕约为剥蚀斑径的14倍; 黄铜矿、磁黄铁矿和闪锌矿元素分馏因子(EFI)约为1.0, 其元素分馏效应可以忽略, 而黄铁矿和辉钼矿存在明显的元素分馏效应. 在对硫化物矿物的LA-ICP-MS分析中, 选择较大的激光剥蚀斑径、较小的激光剥蚀频率与激光能量可获得理想的信号强度和准确的分析结果.     

Some regularities of of laser pyrolysis of polyphenylene- and polyamidocarboranes

Data of laser pyrolysis of carborane-containing polymers are presented in this paper. The main directions of chemical transformations of polyphenylene- and polyamidocarboranes by laser pyrolysis are established. It is proposed to make use of IR laser irradiation for synthesis of secondary polymer structures with specific properties.     

Development of compact coherent EUV source based on laser Compton scattering

High-power extreme ultra-violet (EUV) sources are required for next generation semiconductor lithography. We start to develop a compact EUV source in the spectral range 13–14 nm, which is based on a laser Compton scattering between a 7 MeV micro-bucnhed electron beam and a high-intensity CO₂ laser pulse. The electron beam extracted from a DC photocathode gun is micro-bunched using a laser modulation techinque with the Compton wavelength at a harmonic of the seeding laser before the main laser Compton scattering for EUV generation. A considerating scheme for the compact EUV source based on the laser Compton scattering with micro-bunched electron beam and the analytical study of micro-bunch generation are described in this paper.     

LIF, LEI, RIMS etc. — New promising techniques in elemental micro- and trace analysis

Summary The application of laser spectroscopy in spectrochemistry requires excitation and detection schemes different from the estabolished optical spectrochemical methods. The most promising techniques developed in laser spectrochemistry are described and the analytical figures of merits are discussed. The very low absolute detection limits of the laser methods are required if trace elements have to be measured in microsamples.     

Interface and defects engineering for multilayer laser coatings

High-reflective multilayer laser coatings are widely used in advanced optical systems from high power laser facilities to high precision metrology systems. However, the real interface quality and defects will significantly affect absorption/scattering losses and laser induced damage thresholds of multilayer coatings. With the recent advances in the control of coating design and deposition processes, these coating properties can be significantly improved when properly engineered the interface and defects. This paper reviews the recent progress in the physics of laser damage, optical losses and environmental stability involved in multilayer reflective coatings for high power nanosecond near-infrared lasers. We first provide an overview of the layer growth mechanisms, ways to control the microstructures and reduce layer roughness, as well as the nature of defects which are critical to the optical loss and laser induced damage. Then an overview of interface engineering based on the design of coating structure and the regulation of deposition materials reveals their ability to improve the laser induced damage threshold, reduce the backscattering, and realize the desirable properties of environmental stability and exceptional multifunctionality. Moreover, we describe the recent progress in the laser damage and scattering mechanism of nodule defects and give the approaches to suppress the defect-induced damage and scattering of the multilayer laser coatings. Finally, the present challenges and limitations of high-performance multilayer laser coatings are highlighted, along with the comments on likely trends in future.     

Effect of laser pulse energies in laser induced breakdown spectroscopy in double-pulse configuration

In this paper, the effect of laser pulse energy on double-pulse laser induced breakdown spectroscopy signal is studied. In particular, the energy of the first pulse has been changed, while the second pulse energy is held fixed. A systematic study of the laser induced breakdown spectroscopy signal dependence on the interpulse delay is performed, and the results are compared with the ones obtained with a single laser pulse of energy corresponding to the sum of the two pulses. At the same time, the crater formed at the target surface is studied by video-confocal microscopy, and the variation in crater dimensions is correlated to the enhancement of the laser induced breakdown spectroscopy signal. The results obtained are consistent with the interpretation of the double-pulse laser induced breakdown spectroscopy signal enhancement in terms of the changes in ambient gas pressure produced by the shock wave induced by the first laser pulse.     

Double pulse laser ablation and laser induced breakdown spectroscopy: A modeling investigation

A numerical model, describing laser–solid interaction (i.e., metal target heating, melting and vaporization), vapor plume expansion, plasma formation and laser–plasma interaction, is applied to describe the effects of double pulse (DP) laser ablation and laser induced breakdown spectroscopy (LIBS). Because the model is limited to plume expansion times in the order of (a few) 100 ns in order to produce realistic results, the interpulse delay times are varied between 10 and 100 ns, and the results are compared to the behavior of a single pulse (SP) with the same total energy. It is found that the surface temperature at the maximum is a bit lower in the DP configuration, because of the lower irradiance of one laser pulse, but it remains high during a longer time, because it rises again upon the second laser pulse. Consequently, the target remains for a longer time in the molten state, which suggests that laser ablation in the DP configuration might be more efficient, through the mechanism of splashing of the molten target. The total laser absorption in the plasma is also calculated to be clearly lower in the DP configuration, so that more laser energy can reach the target and give rise to laser ablation. Finally, it is observed that the plume expansion dynamics is characterized by two separate waves, the first one originating from the first laser pulse, and the second (higher) one as a result of the second laser pulse. Initially, the plasma temperature and electron density are somewhat lower than in the SP case, due to the lower energy of one laser pulse. However, they rise again upon the second laser pulse, and after 200 ns, they are therefore somewhat higher than in the SP case. This is especially true for the longer interpulse delay times, and it is expected that these trends will be continued for longer delay times in the μs-range, which are most typically used in DP LIBS, resulting in more intense emission intensities.