Molecular dynamics and control following excitation with an ultra-short intense laser pulse

Vibronic excitations of the tri-atomic molecule OClO (A(2)A(2)(nu(1), nu(2), nu(3)) <-- (XB1)-B-2 (0, 0, 0)) with weak and strong ultra-short laser fields are studied within full quantum wavepacket dynamics in hyperspherical coordinates. Different dynamics is observed following excitation with laser pulses of different intensities. With a strong laser pulse, many vibrational states are excited and a spatially more localised wavepacket arises. The numerical results show that the population of different vibrational states of the wavepacket on the excited potential energy surface is altered by the intensity of the laser pulse. The numerical results also suggest a related effect on the phase of the wavepacket. These interesting phenomena can be understood by an analysis of the corresponding results for two model diatomic molecules. The possible physical mechanisms of control of chemical processes using strong laser fields are discussed. (C) 2004 Elsevier B.V. All rights reserved.

Study of a high power density sodium polysulfide/bromine energy storage cell

Nickel catalyst supported on carbon was made by reduction of nickelous nitrate with hydrogen at high temperature. Ni/ C catalyst characterization was carried out by XRD. It was found that the crystal phase of NiS and NiS2 appeared in the impregnated catalyst. Ni/ C and Pt/ C catalysts gave high performance as the positive and negative electrodes of a sodium polysulfide/ bromine energy storage cell, respectively. The overpotentials of the positive and negative electrodes were investigated. The effect of the electrocatalyst loading and operating temperature on the charge and discharge performance of the cell was investigated. A power density of up to 0.64 W cm(-2) ( V = 1.07 V) was obtained in this energy storage cell. A cell potential efficiency of up to 88.2% was obtained when both charge and discharge current densities were 0.1 A cm(-2).

Control of chemical reaction in high-intensity laser field

The prospects of control chemical reaction in high-intensity laser field are talked about here, and some experimental and theoretical designs are reviewed and discussed also.

Carbon Nanotube/Silica Coaxial Nanocable as a Three-Dimensional Support for Loading Diverse Ultra-High-Density Metal Nanostructures: Facile Preparation and Use as Enhanced Materials for Electrochemical Devices and SERS

In this paper, we have reported a very simple strategy (combined sonication with sol-gel techniques) for synthesizing well-defined silica-coated carbon nanotube (CNT) coaxial nanocable without prior CNT functionalization. After functionalization with NH2 group, the CNT/silica coaxial nanocable has been employed as a three-dimensional support for loading ultra-high-density metal or hybrid nanoparticles (NPs) such as gold NPs, Au/Pt hybrid NPs, Pt hollow NPs, and Au/Ag core/shell NPs. Most importantly, it is found that the ultra-high-density Au/Pt NPs supported on coaxial nanocables (UASCN) could be used as enhanced materials for constructing electrochemical devices with high performance. Four model probe molecules (O-2, CH3OH, H2O2, and NH2NH2) have been investigated on UASCN-modified glassy carbon electrode (GCE). It was observed that the present UASCN exhibited high electrocatalytic activity toward diverse molecules and was a promising electrocatalyst for constructing electrochemical devices with high performance. For instance, the detection limit for H2O2 with a signal-to-noise ratio of 3 was found to be 0.3 mu M, which was lower than certain enzyme-based biosensors.

Studies on the nature of the macromolecular condensed state of "nascent" ultra high molar mass polyethylene

Ultra high molar mass polyethylene (UHPE) powder as polymerized in a slurry process has been studied, in its nascent state, after recrystallization on rapid cooling from the melt and after hot compression molding to a film, by DSC, effect of annealing the recrystallized specimen at 120 similar to 130 degreesC, morphology by polarizing optical microscopy and small angle X-ray scattering. Based on the experimental results obtained the macromolecular condensed state of the nascent UHPE powder is a rare case of a multi-chain condensed state of non-interpenetrating chains, involving interlaced extended chain crystalline layers and relaxed parallel chain amorphous layers. On melting, a nematic rubbery state of nanometer size domain resulted. The nematic-isotropic transition temperature was judged from literature data to be at least 220 degreesC, possibly higher than 300 degreesC, the exact temperature is however not sue because of chain degradation at such high temperatures. The recrystallization process from the melt is a crystallization from a nematic rubbery state. The drop of remelting peak temperature by 10 K of the specimen recrystallized from its melt as compared to the nascent state has its origin in the decrease both of the crystalline chain stem length and of the degree of crystallinity. The remelting peak temperature could be returned close to that of the nascent state by annealing at 120 similar to 130 degreesC.

Mechanical and structural characteristics of phenolphthalein poly(ether sulfone) ultra-high molecular weight polyethylene blends

Mechanical and structural properties of blends of phenolphthalein poly(ether sulfone) (PBS-C) with ultra-high molecular weight polyethylene (UHMWPE) were investigated using tensile and bending testing, scanning electron microscopy and transition electron microscopy. The incorporation of minor amounts of UHMWPE (2 wt.-%) into PES-C has a reinforcement effect. With higher concentrations of UHMWPE, the mechanical properties decrease gradually. Structural studies demonstrated that the blends are multiphasic in the whole composition range. The minor UHMWPE, dispersed uniformly and oriented along the flow direction, as well as the strong interfacial adhesion contribute to the increase of the mechanical performance of the blends. The domain size of the UHMWPE phase was found to increase with the increase of its concentration.

柔性加工中高功率激光束空间变换研究

在国民经济中占有重要地位的汽车工业中，对于大型覆盖件模具的表面强化处理，最常见的是火焰淬火。火焰淬火对操作人员的要求高，可控性差，效果不理想，但是由于一直没有适合的方法，目前也只能继续使用。而激光表面强化技术结合柔性加工系统正是解决这类问题的新途径。传统的激光表面强化是采用把激光束离焦后进行扫描的方式，这种方法不能充分利用激光功率密度，而且往往要用转镜或振镜形成条形光斑来加快处理速度，这就需要复杂的机械结构，而且产生难以避免的重叠回火。我们提出一种新方法，利用二元光学元件来获得一种新型的周期光强分布，实现其在高功率激光系统中的应用，并设计成为集成到柔性加工系统中的组成部分，能够完成对大、中型模具表面的激光强化处理。本论文的工作主要是有关激光柔性加工系统中的光束传输及变换子系统，不仅包括理论设计、加工制作，同时还包括把该子系统有效的结合到整个系统中。本研究工作广泛涉及激光理论，光束变换和光纤传输，系统中的模块化集成应用技术，金属材料的特殊分布光强表面改性试验研究等等，是跨学科的交叉研究工作。在本论文中，重点是二元光学元件的设计方法的选择、计算机辅助设计的实现、二元光学元件的制作和在高功率激光传输中的应用，以及特殊光强分布应用于金属表面改性中的相关工作。通过把二元光学元件引入到高功率激光加工中，对出现的新现象给出一定的预测和分析，并获得了良好的强化结果，最终实现了系统的集成化，并具有实际生产所要求的可靠性和灵活性。本论文共分六章，主要包括两方面的内容。第一章为绪论，第六章为结论。第一方面内容在第二章到第四章中说明，是用于高功率激光应用中的二元光学元件的原理、设计和制作。第二方面的内容在第五章中，是关于应用前面设计制作的二元光学元件，在实际的金属材料表面处理中的实验研究，给出了相关试验结果。

激光聚焦爆炸耦合场的理论建模与跨尺度计算

针对激光聚焦爆炸的电磁-热力耦合效应,在宏观尺度上,把描述激光电磁波散射和传播的Maxwell方程和高温高压气动流场的Euler方程结合起米,利用热力学状态方程(EOS)和电离平衡方程(Saha方程)并通过理论建模和数值仿真,研究和揭示激光聚焦爆炸效应及激光支持吸收波(LSC/LSD)的产生和演化、以及相关的反冲压力和动量耦合等相互作用机制.

基于强激光辐照固体锡靶产生极紫外光源的实验研究

建立了一套利用高功率YAG激光器辐照固体锡靶产生高转换效率极紫外光(extreme ultraviolet)源的实验装置.利用建立的实验装置开展了极紫外光源的强度和转换效率与抽运激光强度关系的实验研究,发现极紫外光源的转换效率随抽运激光强度的变化具有饱和效应.实验发现:当抽运激光能量达到250mJ时,极紫外光源的转换效率最高,波长为13.5nm处0.27nm带宽范围内的极紫外光源的能量转换效率为1.6%,此时对应的激光强度为1.8×1011W/cm2.

图像处理在光路自动准直系统中的应用

光路自动准直系统应用于惯性约束聚变的高功率激光装置中的光束自动调整。图像处理是光路自动准直的关键技术之一。针对神光Ⅲ原型装置，结合阈值化、重心法、中值滤波和圆拟合等多种不同的图像处理方法设计了一套合理的准直方案，并且在模拟实验平台上进行了实验验证。实验结果表明，光路自动准直系统能够在15min之内顺利完成光路的自动调整，光束近场调整精度优于近场光斑的±0．5％，光束远场调整精度≤±0．3″，满足了原型装置的总体要求。

偏振分配角θp对高功率激光三倍频波形的影响

使用四阶龙格-库塔算法数值求解Ⅱ类-Ⅱ类偏振失配方案的三倍频稳态耦合波方程组。针对“神光Ⅱ”激光驱动器的三倍频系统，在二倍频匹配角吼和三倍频匹配角只均处于最佳匹配情况下，以1°为单位改变偏振分配角郇的偏离量，得到对应的三倍频波形特性的变化。研究表明，偏振分配角θp处于最佳理论匹配位时，对应的三倍频波形半峰全宽最窄，且波形上升沿抬起也最快；θp从最佳匹配位增加比从最佳匹配位减小对应的半峰全宽变宽更快，对应的上升沿抬起更慢。根据所得理论结果，在实验中调节偏振分配角θp，达到了改变三倍频输出波形特性，进而实现八

磷酸盐激光玻璃聚（CH3）2Si（OC2H5）2防潮膜

以（CH3）2Si（OC2H5）2为前驱体，采用溶胶-凝胶与有机合成相结合的方法，制得稳定性良好的涂膜液。采用旋转涂膜法在掺钕磷酸盐激光玻璃棒端面涂制防潮膜，膜层固化后透过率达96．5％，获得的膜层表面粗糙度优良，均方根表面粗糙度（RMS）为1．659nm，平均粗糙度（RA）平均为1．321nm；在激光波长1053nm，脉冲宽度1 ns条件下膜层的激光破坏闽值可达10～14 J／cm^2。经过“神光Ⅱ”高功率激光器物理实验运行，膜层使用期为五年，并且已经在我国“神光Ⅲ”原型装置上试用。

列阵透镜对能量测量影响的分析

结合列阵透镜的透过率分析了其后的光场分布。列阵透镜由多个列阵元拼接而成，用以改善主透镜焦点附近能量分布的均匀性。列阵透镜在提高辐照均匀性的同时，给能量测量带来了不利的影响。这是由于经过列阵元的相邻子光束会产生干涉，干涉条纹处的激光能量密度和功率密度相应都大为增加，其数值在干涉区域中心处能上升到原来的4倍。更高的能量密度和功率密度对能量计提出了更苛刻的要求。在没有采取适当措施的时候使用，就会损坏能量计。