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  • What is X-ray diffraction, and what is it used for?

    什麽是X光繞射(XRD)?它能夠做什麽?在 X 光繞射實驗中,

  • In an X-ray diffraction experiment, a sample is placed into the center of an instrument and illuminated with a beam of X-rays.

    樣品放置在儀器的中心,受到一束 X 光照射。

  • The X-ray tube and detector move in a synchronized motion.

    X 光光管和探測器同步的移動,

  • The signal coming from the sample is recorded and graphed,


  • where peaks are observed related to the atomic structure of the sample.


  • Most materials are made up of many small crystals like sand on a beach.

    大多數的材料都是由許多小晶體組成的, 這就像沙灘上的沙一樣。

  • Each of these crystals is composed of a regular arrangement of atoms,


  • and each atom is composed of a nucleus surrounded by a cloud of electrons.


  • It's at this scale that the story of X-ray diffraction begins.

    X 光繞射就是在這個原子尺度下發生的。

  • X-rays are high-energy light with a repeating period called the wavelength.

    X 光是一種周期性高能光束線,它的周期稱爲波長。

  • Since the wavelength of an X-ray is similar to the distance between atoms in a crystal,

    由於 X 光的波長與晶體中的原子間距接近,

  • a special interference effect called "diffraction" can be used to measure the distance between the atoms.

    形成了一種可以利用來量測原子間距的特殊干涉現象, 稱爲繞射。

  • Interference occurs when X-rays interact with each other.


  • If the waves are in alignment, the signal is amplified. This is called "constructive interference".


  • If the waves are out of alignment, the signal is destroyed. This is called "destructive interference".


  • When an X-ray encounters an atom, its energy is absorbed by the electrons.


  • Electrons occupy special energy states around an atom. Since this is not enough energy for the electron to be released,


  • the energy must be re-emitted in the form of a new X-ray, but the same energy as the original.

    這些能量會以二次 X 光的形式釋放,能量大小與原始 X 光相同。

  • This process is called "elastic scattering".


  • In a crystal, the repeating arrangement of atoms form distinct planes separated by well-defined distances.


  • When the atomic planes are exposed to an X-ray beam, X-rays are scattered by the regularly spaced atoms.

    當 X 光照射到晶面,就會被規則排列的原子散射。

  • Strong amplification of the emitted signal occurs at very specific angles

    散射 X 光會在特定的角度產生非常强烈的建設性干涉訊號。

  • where the scattered waves constructively interfere. This effect is called "diffraction".


  • The angle between the incident and the scattered beam is called 2-theta.

    入射光和散射光之間的夾角稱爲 2theta 角。

  • In order for constructive interference to occur, the scattered waves must be in alignment,


  • meaning that the second wave must travel a whole number of wavelengths.


  • In this case, one half of a wavelength is traveled on the incident side,


  • and one half on the scattered side, yielding one additional wavelength.


  • In the case of the next X-ray, one wavelength has traveled on

    這樣就有兩個波長的光程差。 這樣的叠加現象會在整個晶體裏出現,

  • both the incident and the scattered side resulting in two wavelengths.


  • This reinforcement occurs throughout the crystal.

    三角形上方的角度稱爲 theta 角, 是入射光跟散射光之間夾角的一半。

  • The exact angle at which diffraction occurs will be determined from the red triangle.


  • The angle at the top is theta, half the angle between the incident and scattered beams.


  • The long side is the distance between the atomic planes and the short side we know is one half of a wavelength.

    如果我們把等式移項就能得到布拉格定律(Bragg's Law)。

  • The relationship between the diffraction angle,

    這個定律是以 Sir William Henry Bragg 和 William Lawrence Bragg 這對父子檔命名的。

  • and the spacing between the atoms can be determined by applying the sine function.

    他們在 1915 年因爲X光繞射在晶體結構分析的成就, 得到諾貝爾獎。

  • Rearranging this equation yields an equation commonly known as "Bragg's Law",


  • named after Sir William Henry and William Lawrence Bragg, the father-son team who won the Nobel Prize in 1915


  • for their work analyzing crystal structures with X-ray diffraction.


  • This technique of X-ray diffraction is used today for a wide variety of materials, ranging from


  • single crystal epitaxial thin films, to polycrystalline mixtures of powders, and even randomly oriented amorphous materials.


  • X-ray diffraction helps scientists to develop new pharmaceuticals, classify rock formations


  • based on their mineral components and understand how the arrangement of atoms


  • affects the behavior of energy storage materials.

    先進的儀器設計讓X光繞射分析更易於使用, 功能也越來越强大。

  • As scientists push their ability to engineer materials on the atomic level,

  • X-ray diffraction becomes an increasingly important tool in their toolbox.

  • Advances in equipment design have made X-ray diffraction easier to use, and more powerful than ever.

What is X-ray diffraction, and what is it used for?

什麽是X光繞射(XRD)?它能夠做什麽?在 X 光繞射實驗中,


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什麽是X光繞射(What is X-ray Diffraction?)

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    lovegastar 發佈於 2022 年 08 月 04 日