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在电子能量损失谱中电离损失峰高能损失一侧的几百电子伏特范围内,有很弱的振荡信号,被称之为广延精细结构,英文缩写为EXELFS。我们可以从EXELFS获得中心原子的性质及其配位原子的配位距离(即径向分布函数)和原子性质等结构信息。EXELFS的产生原理和分析方法都和EXAFS(X-射线吸收限广延精细结构)有很大相似之处,同时又有许多自己的独到之处。EXELFS适于对非晶态等短程序材料进行结构分析,可以结合电镜上获得的其他信息对材料进行综合分析。近几年来,国外在EXELFS这个领域内开展了不少工作。作者对M.DISKO的EXELFS付立叶分析计算机程序进行了修改和调整;增加了ELS本底扣除,门槛值E_o的确定等程序段,删掉了径向分布函数的低频滤波的程序段;另外,更正了原程序中的几处错误。修改后的付立叶分析程序包括以下几个步骤:
In the electron energy loss spectrum, the peak of ionization loss in the energy loss side of hundreds of electron volts range, there is a weak oscillation signal, is called the extended fine structure, the English abbreviation EXELFS. From EXELFS, we can obtain the structure of the central atom and its coordination distance (ie, radial distribution function) and the atomic properties of the central atom. EXELFS generation principle and analytical methods and EXAFS (X-ray absorption limit extended fine structure) has a lot of similarities, but also has its own uniqueness. EXELFS is suitable for structural analysis of amorphous materials such as short procedures, combined with other information obtained on the electron microscope for comprehensive analysis of the material. In recent years, foreign countries have done a lot of work in the field of EXELFS. The author modified and adjusted M.DISKO’s EXELFS Fourier analysis computer program, added ELS background subtraction, threshold value E_o determination and other blocks, deleted the radial distribution function of the low-frequency filtering of the program segment; the other , Correct a few mistakes in the original program. The modified Fourier analysis program includes the following steps: