在前期计算电子能量分布函数的基础上，求出弱电离大气等离子体中各碰撞反应过程的电子能量损失.由于在弹性碰撞中电子-重粒子能量交换很少，同时氮气、氧气分子又有很多能量阈值较低的转动、振动能级存在，因此在大气等离子体中弹性碰撞电子能量损失所占份额很小(直流电场下小于6%).研究发现，弱电离大气等离子体中在不同能量区间占主导的能量损失过程不同.随着有效电子温度(或约化场强)增加，占主导的电子能量损失过程依次为转动激发、振动激发、电子态激发、碰撞电离、加速电离产生的二次电子.在约化场强E/N=1350 Td (或有效电子温度为14 eV)附近，平均电离一个电子所需的能量最小，约为57 eV.因此可以根据不同的需求调节电场强度，从而达到较高的能量利用率.

The energy loss induced by electron collisions in weakly ionized air plasma is calculated based on the electron energy dis-tribution function that we obtained. Since there are a lot of low-energy-threshold molecular rotation and vibration excitations and the electron-molecule energy transfer is inefficient in elastic collision, the fraction of energy loss for electron elastic collision (less than 6%) is negligible. Among different collision processes the electron energy loss is dominant in different energy regions. As the effective electron temperature (or the reduced electric field) increases, the dominant energy loss process becomes sequentially rota-tional excitation, vibrational excitation, electronic excitation, collisional ionization, and accelerating ionized electrons. When E/N=1350 Td (or Te =14 eV), the average energy loss per ion-electron pair reaches a minimum value of 57 eV. By controlling the electric field according to the requirement in applications, we can control the e

扫描透射电子显微镜是透射电子显微镜的一种,近几年随着球差校正器的问世,扫描透射电子显微镜的分辨率达到亚埃级,结合能量分辨率为亚电子伏特的电子能量损失谱,可以对材料进行高空间分辨率及高能量分辨率的微结构和成分分析。文章简述了扫描透射电子显微镜的发展历程和工作原理,重点讲述了高角环形暗场像的成像机理以及基于高角环形暗场像对材料结构和成分进行分析的原理和应用;电子能量损失谱的成谱过程、谱的特征及其在材料化学和电子结构分析方面的优势和主要应用。

The scanning transmission electron microscope (STEM) is one kind of trans-mission electron microscope. With the invention of the spherical aberration corrector, the resolu-tion of STEM can reach sub-?ngstrom levels. High spatial resolution imaging and high energy resolution spectroscopy can be achieved simultaneously through the combination of STEM and electron energy loss spectroscopy (EELS). The fundamentals and application of STEM will be briefly introduced, with emphasis on the basics of high angle annular dark field imaging and its application in microstructural and chemical analyses. The characteristic features of EELS and its application in material science will also be discussed.

利用基于密度泛函理论的第一性原理方法对黑索金晶体的电子结构和光学性质进行了计算.结果表明：黑索金是能隙值为3.43 eV的绝缘体,价带主要由C, N和O的2s与2p态构成,而导带主要由N-2p和O-2p态构成；静态介电函数ε1(0)=1.38,介电常数的虚部有5个峰值,其中最大峰值在光子能量4.59 eV处,并对造成这些峰值的可能的电子跃迁做了详细分析.利用能带结构和态密度分析了黑索金的光反射系数、吸收系数及能量损失函数等光学性质,发现黑索金是对光吸收、反射及能量损失不敏感的材料.

Electronic structure and optical properties of RDX are calculated by the first-principle density function theory pseudopotential method. The calculated results show that RDX is an insulator with a band gap of 3.43 eV, that the valence band of RDX is mainly composed of C-2s, C-2p, N-2s, N-2p and O-2s, O-2p, and that the conduction bands are mainly composed of N-2p and O-2p. The static dielectric functionε1 (0) is 1.38, the imaginary part of dielectric function has five peaks and the largest peak is at the position corresponding to 4.6 eV of photon energy. The electronic direct transitions for these peaks are analyzed in detail. The absorption, reflectivity and loss function of RDX are analyzed in terms of calculated band structure and density of states. The results indicate that the RDX is not sensitive to the optical absorption nor to reflectivity nor to energy loss.

卤素氟化物是一类反应活性很强的物质,在诸多领域中有重要作用。利用高分辨快电子能量损失谱仪,采用高分辨的dipole(e,e)方法可对卤素氟化物的分子荧光光谱振子强度进行了分析,其避免了光学测量过程中存在的精度低、效率低的缺陷。在21~26 e V的能量损失区域中,检测获取卤素氟化物卤素氟化物分子荧光光谱的11S→n1P跃迁以及电离过程的光学振子强度谱,并在59~67 e V和69~74 e V的能量损失区域中,分析卤素氟化物分子荧光光谱的自电离共振过程的光学振子强度谱,实验将得到的结果同前人研究成果进行对比分析,实验结果说明所提方法获取的卤素氟化物分子荧光光谱的振子强度,同前人研究结果具有较高的匹配度,具有较高的应用价值。

Fluoride is a kind of reactive halogen material, plays an important role in many fields. Using high resolution fast electron energy loss spectrometer, USES the high resolution of dipole (e, e) method for halogen fluoride molecule fluorescence spectrum oscillator strength are analyzed, and it avoids the existing in the process of optical measurement of the defects of low precision and low efficiency. In 21~26 ev energy loss in the area of detection for halogen halogen fluoride fluoride molecule fluorescence spectrum of optical oscillator strength of the process of transition and ionization spectrometry, and 59 ~67 ev and 69 ~ 67 ev energy loss in the area, the analysis of fluoride halide molecule fluorescence spectrum of optical oscillator strength of the process of autoionization resonance spectrum, the experiment will receive the results with previous research results, this paper compares and analyzes the experimental results show that the proposed method to obtain the fluor

文章简要介绍了材料科学研究中被广泛应用的透射电子显微(TEM)技术及其在多铁材料研究中的应用,并给出了几个典型案例:利用球差矫正原子分辨扫描透射电子显微术(STEM),并和电子能量损失谱(EELS)相结合,分析多铁异质结界面处的原子分布、离子价态和化学键的变化;结合球差矫正原子分辨透射电子显微图像(HRTEM)和STEM图像,分析多铁材料中的局域对称性破缺和电极化特性;利用原位变温及电/磁场加载技术,研究多铁材料中的结构相变和电畴/磁畴的动态演变特性。文章特别指出,现代透射电子显微学是全面分析理解多铁材料局域微结构,探讨多铁耦合机制及其物理根源的有效手段。

Recent progress of a variety of modern transmission electron microscopy (TEM) techniques and their applications to multiferroic materials are briefly reviewed. It is empha-sized that numerous significant structural issues in multiferroic material science could be well ad-dressed by means of TEM-based techniques. For instance, atomic-resolution scanning transmis-sion electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) are invaluable for determining the atomic structure, valence states and electronic structure of the controllable in-terface in multiferroic heterostructures. High-quality high-resolution TEM and STEM images with spatial resolution better than 1 ? ensure the direct observation of local dipoles and mapping of the polarization field. The new generation TEM facilities combined with in-situ cooling/heating and electric/magnetic field holders allow us to capture the dynamic characteristics of the atomic struc-ture and ferroelectric/magnetic domains and to und