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Characteristic Spectrum and the K-alpha line

  1. Oct 17, 2014 #1
    I have just finished a junior-level lab assignment in which we used X-ray diffraction to determine the lattice constants of unknown materials. In the theory section of the lab write-up, it briefly explains the K-alpha doublet of the characteristic spectrum. I understand that it is the result of a vacancy in the K shell being filled from the L shell, and I understand that the two lines (Kα1 and Kα2) can appear as a single, unresolved line which is taken as the weighted average of the two lines. What I don't understand is why the Kα1 line is always twice as strong as the Kα2 line. I have read through the section on the characteristic spectrum in {Cullity, B.D. Elements of X-Ray Diffraction. 3ed. Prentice Hall, 2001} and I am still a little confused. Is this just an experimentally observed fact?
  2. jcsd
  3. Oct 17, 2014 #2
    For Kα1 the total angular momentum of the initial state is 3/2, this has states with Jz components of 3/2,1/2,-1/2,-3/2. In comparison the inital states for kα2 emission have a total angular momentum of 1/2 which has Jz values of 1/2,-1/2. Thus there are twice as many states which for the electron to decay to by emitting Kα1 than Kα2.
  4. Oct 17, 2014 #3
    Thanks a lot, Vagn, that is actually pretty straight-forward. Cheers!
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