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In the X-ray experiment , a sample is placed into the center of an instrument and illuminated with a beam of X-rays. 在X射… 文章目录 实验过程原理晶体构成X射线波长diffraction 干涉效应 Braggs Law晶体间距d散射角度θ半波长λ/2公式 公式名称由来应用设备 实验过程
In the X-ray experiment , a sample is placed into the center of an instrument and illuminated with a beam of X-rays. 在X射线实验中一个样品放在一起中间并且由一束X射线照亮。
The X-ray tube and detector move in a synchronized motion. X射线和探测器以同步运动的方式移动。
The signal coming from the sample is recorded and graphed , where peaks are observed related to the atomic structure of the sample. 来自样品的信号被记录和绘制下来,其中峰值被观察到是与样品的原子结构相关。
原理
晶体构成
Most materials are made up of many small crystals like sand on a beach. 大多数材料由很多小的晶体构成就像沙滩上的沙子。 Each of these crystals is composed of a regular arrangement of atoms. 每一个晶体都由规则排列的原子构成。 and each atom is composed of a nucleus surrounded by a cloud of electrons. 每个原子都由一个被电子云环绕的原子核构成。
X射线波长
X-ray are high-energy light with a repeating period called tthe wavelength since the wavelength of an X-ray is similar to the distance between atoms in a crystal . X射线是具有重复周期的高能光。称为波长因为X射线的波长类似于晶体中的原子间距。 diffraction 干涉效应
a special interference effect callled diffraction can be used to measure the distance between the atoms. 一种称为衍射的特殊干涉效应这种效应可以用来测量原子间的距离。 Interference occurs when X-ray interact with each other. 干涉发生在X射线相互作用。 If the waves are in alignment , the signal is amplified. 如果波对齐一致那么信号就被放大。 This is called constructive interference. 这称为下相干干涉。
If the wave are out of alignment , the signal is destroyed .this is called destructive interference. 如果波不对齐信号被破坏。这称为相消干涉。 When an X-ray encounters an atom , its energy is absorbed by the electrons. 当X射线遇到原子时能量被电子吸收。 Electrons occupy special energy states around an atom 电子占据原子周围特殊的能级状态 since this is not enough energy for the electron to be released, 由于没有足够的能量释放电子 the energy must be re-emitted in the form of a new X-ray with the same energy as the original. 能量必须以一种新的X射线的形式重新发射,其能量与原始能量相同。
This process is called elastic scattering , 这个过程称为弹性散射。
Bragg’s Law
晶体间距d
In a crystal , the repeating arrangement of atoms form distinct planes seperated by well-defined distances. 在一个晶体中重复排列的原子形成由明确的距离分隔的不同平面。
散射角度θ
When the atomic planes are exposed to an X-ray beam , 当原子平面暴露于X射线束时 X-ray are scattered by the regularly spaced atoms X射线会被规则间隔的原子散射。 Strong amplication of the emitted signal occurs at very specific angles , 发射信号的强烈放大发生在非常特定的角度 where the scattered waves constructively interfere, 其中散射波相长干涉 this effect is called diffraction, 这种效应称为衍射 the angle between the incident and the scattered beam , 入射光束和散射光束的角度为2θ
半波长λ/2
in order for constructive interference to occur, 为了发生相干干涉 the scattered waves must be in alignment 散射波必须对齐 meaning that the second wave must travel a whole number of wavelengths. 这意味着第二波必须传整数个波长。 In this case , one half of a wavelength is traveled on the incident side , 在这种情况下一般波长在入射侧传播 and one half on the scattering side yielding one additional wavelength. 一半在散射侧传播,产生一个额外的波长。
公式
In the case of the next X-ray, 在下一个X射线的情况下 one wavelength is traveled on both the incident and the scattered side. 一个波长在入射侧和散射侧传播 resulting in two wavelengths, 产生两个波长 This reinforcement occurs throughout the crystal, 这种增强发生在整个晶体中 the exact angle at which diffraction occurs can be determinded from the red triangle. 即衍射发生的确切角度可以从红色三角确定。 The angle at the top is θ half the angle between the inicdent and scattered beams. 顶部的角度是θ即入射光束和散射光束之间角度的一半。 The long side is the distance between the atomic planes, 长边是原子平面之间的距离 and the short side we know is one half of a wavelength. 我们知道的短波是长波的一半。 The relationship between the diffraction angle and the spacing between the atoms can be determined by applying the sin function. 在衍射角和原子间的距离的关系可以通过sin方程确定。 rearranging this equation yields an equation commonly known as Bragg’s Law. 重新排列这个方程得到一个方程,通常被称为布拉格方程。
公式名称由来
named after sir William Henry and William Lawrence Bragg. 以William Henry和William Lawrence Bragg命名。 a father-son team who won the Nobel Prize in 1915 for their work analyzing 这个父子组合因为他们的分析工作获得了诺贝尔奖。 crystal structures with X-ray Diffraction. (分析)晶体结构用的是X射线衍射。
应用
This technique of X-ray diffraction is used today for a wide variety of materials, 如今这种X射线衍射技术用于广泛的材料。 ranging from single crystal expitacial thin films , 从单晶外延薄膜到粉末的多晶混合物 and even randomly oriented to amorphous materials. 甚至随机取向的非晶材料。
X-ray diffraction helps scientists to develop new pharmaceuticials, X射线衍射帮助科学家开发新药物 classify rock formations based on their mineral components, 根据矿物成分对岩石层进行分类 and understand how the arrangement of atoms affects the behaviour of energy storage materials. 并了解原子排列如何影响储能材料的行为。
设备
as scientists push their ability to engineer materials on the atomic level, 随着科学家们在原子水平上提高材料工程能力 X-ray diffraction becomes an increasingly important tool in their toolbox, X射线衍射成为他们工具箱中越来越重要的工具。
Advances in equipment design have made X-ray diffraction easier to use, 设备设计的进步让X射线衍射更易于使用 and more powerful than ever. 并且比以往更加强大。
