来自《耶鲁大学开放课程：新生有机化学 第5集 第5集》

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  So all electrons on a plane perpendicular to the scattering vector,
  所以垂直于散射矢量方向上的所有电子
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  scatter in-phase at the specular angle.
  在镜象方向上的散射光相位相同
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  Now suppose you have a whole bunch of electrons
  现在 如果你有许多电子
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  you have to figure out how they're going to reinforce or cancel one another.
  你需要弄清楚它们之间的相互关系
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  There's a trick you can use.
  这里有一个小技巧
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  You see if you can discern a set of planes that are evenly spaced
  先看看能否找到一系列间距相等的平面
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  that contain all, or almost all, of the electrons you're interested in.
  使所有电子 或多数电子都包含在其中
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  Okay, now if you look at this pattern,
  就以这个图案为例
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  you can see that there's a set of planes, equally spaced,
  可以想到有一些间距相等的平面
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  that passes through all of them.
  使所有电子都包含在其中
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  Can you perceive it?
  你们能想象出来吗?
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  There.
  就像这样