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X ray crystallography - interpreting my graph

  1. Oct 13, 2016 #1
    1. The problem statement, all variables and given/known data
    I am currently part way through a laboratory experiment that utilises basic crystallography to ultimately calculate lattice constants and structure factors for NaCl (we receive formal training in the next academic year via full treatment of von Laue, Bragg diffraction etc).
    I have consulted a couple of recommended text books, but nothing addresses my concerns.
    Our X ray spectrometer his an unfiltered Molybdenum anode lamp. The goniometer is geared to maintain the Bragg geometry (Geiger tube turns at twice angular speed of table).

    The plot for scanning across angles for a NaCl crystal is shown below.

    Now here is my major query:
    Bremsstrahlung with Mo {k_alpha and k_beta} emission lines are incident on the NaCl.
    • What use it is having a continuous spectrum incident on the crystal? I thought standard practise is to attenuate with say a Zr absorber foil via the absorption principle?
    • Why is bremsstrahlung *detected* - I thought it is just produced by the Mo anode in etc X ray tube?
    • Not knowing precisely what each pair of peaks (of diminishing intensity) shows, I do not know how to calculate d_hkl from this plot
    Kf8UF0N.png


    2. Relevant equations
    [itex]n\lambda =2d_{hkl}\sin \theta [/itex]

    3. The attempt at a solution
     
  2. jcsd
  3. Oct 18, 2016 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
     
  4. Oct 19, 2016 #3

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Depends on your application I think.
    It is produced in the x-ray tube and scattered in the NaCl crystal. Where is the problem?
    You can look up the spectrum for Molybdenum anodes. There are two very prominent peaks.
     
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