用拉盖尔-高斯激光对真空中电子直接加速

对用拉盖尔-高斯(LG)光束加速电子作了研究.结果表明，仅模指数为p和l=1的LG光束的纵向电场可用于加速电子.模指数为p和l=1的线偏振和圆偏振LG光束都对电子有加速效果.对轴上光场的相速度和群速度以及电子能量增益等物理特征作了讨论.给出了轴上光场的相速度和群速度、加速电位及电子能量增益等的解析表达式，并作了数值计算和分析. 关键词： 激光电子加速 拉盖尔-高斯光束 线偏振和圆偏振 能量增益     

The origin of the formation of cavities in galvanized coatings

The role of water‐soluble corrosion products on galvanized wires was examined. The samples used were industrial hot‐dip galvanized wires, which were exposed to the open air under all weather conditions for a relatively short time (6 and 12 months), in an urban environment close to the sea. The samples were studied by different methods, i.e. scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and optical microscopy (OM). Several phases were detected because of the galvanization procedure and the steel substrate. Furthermore, phases which were formed as a result of the reaction of zinc with the atmosphere were also detected. These were oxides like ZnO, carbonates like ZnCO₃ and hydrated Zn and Fe sulfates. Their presence influences the corrosion resistance of the wires, which finally, strongly depends on the solubility of the wires in water. The SO₄^2? compounds especially are very soluble and consequently are easily removed from the coating surface, leading to its degradation by the formation of cavities. In any case, their presence, even after a short period of exposure, implies that the coating is highly affected by the atmosphere of the modern city. Copyright © 2006 John Wiley & Sons, Ltd.     

40Ar+诱导无定形碳到金刚石纳米晶相变的研究

通过60 keV的⁴⁰Ar⁺辐照无定形碳靶合成了大量尺寸不同的金刚石纳米颗粒.高分辨透射电子显微镜配合能量色散X射线谱和电子衍射以及Raman谱分析的结果表明，这些嵌于具有扰动石墨结构薄膜中的纳米金刚石颗粒，其成核率很高(约为10¹³/cm²)，而且可以生长到较大的尺寸，有的甚至可以达到微米量级.对其相转变过程也进行了初步探讨. 关键词： 离子束 金刚石纳米晶 相变 透射电子显微镜     

二分量高温超导机理

用两种电子态,讨论了金属—绝缘相变、反铁磁性—金属相变,以及相分离、正常态—超导态相变、非费米液体行为、高Tc等 关键词： 两种电子态 格林函数 玻色化 高温超导     

低速高电荷态离子40Ar16+与云母表面作用中的电子发射研究

报道了由兰州ECR源提供的低速高电荷离子40Ar16 入射到云母表面产生的电子发射的实验测量结果.结果发现,电子发射产额Y与离子入射角ψ有近似1/tanψ的关系.基于经典过垒模型,我们对这一关系进行了理论分析.实验结果和理论结果相当符合,这就间接说明势能电子发射是低速高电荷态离子作用于表面发射电子的一个主要途径.     

The structure of monolayer SiO2 on Mo(1 1 2): A 2-D [Si-O-Si] network or isolated [SiO4] units?

In this letter, atomically resolved scanning tunneling microscopic (STM) images obtained from monolayer SiO₂/Mo(1 1 2) are presented. The results are consistent with a previously proposed structural model of isolated [SiO₄] units based on vibrational features observed by high-resolution electron energy loss spectroscopy (HREELS) and infrared reflection-absorption spectroscopy (IRAS), and oxygen species identified by ultra-violet photoemission spectroscopy (UPS). These results are inconsistent with a structural model that assumes a two-dimensional (2-D) [Si-O-Si] network. These data illustrate that a metal substrate, although coated with an oxide thin layer, can be directly imaged at the atomic-scale with STM.     

磁场下含结构缺陷多组分超晶格中的局域电子态和电子输运

在有效质量近似理论下，利用转移矩阵和有效垒高方法研究了有限磁场下含结构缺陷的多组分超晶格中局域电子态的性质.在考虑各组分层有效质量的失配时，外加磁场会导致磁耦合效应的出现.磁耦合效应不仅引起局域电子能级的量子化，并且随着朗道指数或磁场强弱的变化，局域能级及其局域程度都会发生显著移动，特别是对高能区域的局域电子态影响更大.此外，还计算了电子输运系数，讨论了含结构缺陷的三组分超晶格中局域电子能级与输运谱透射禁区中的共振透射峰的关系，发现两者之间有着很好的对应关系，为相应的实验研究提供了依据. 关键词： 超晶格 局域电子态 磁场     

金锥对靶背向超热电子分布的影响

 采用20 TW啁啾脉冲放大的ps激光辐照金锥靶和平面靶，对靶背向产生的超热电子角分布和能谱进行了实验研究。结果表明:金锥对超热电子的产生具有重要的影响。与平面靶情况相比，锥形靶靶背向产生的超热电子数量增加，电子能量为2.0~2.5 MeV的超热电子数目有大幅度增长；锥形靶背向超热电子的空间发散角大于平面靶,这是由于啁啾脉冲放大激光所固有的较高脉冲前沿产生的预等离子体造成的影响。     

外加电场下激光诱导Al等离子体特性的实验研究

由Q-Nd:YAG脉冲激光(波长1.06μm,脉宽10 ns)烧蚀Al靶产生等离子体.观测了在低气压和直流电场条件下的Al等离子体发射光谱.研究了激光功率密度和直流电场对各谱线强度的影响,分析了谱线半高全宽与外加电压,等离子体电子温度与激光能量的变化规律.结果表明,直流电场对铝原子谱线强度有显著的增强,铝原子谱线的半高全宽与直流电场的外加电压基本上呈线性关系.