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Why the photoelectric cross section decreases with the energy of the photon?

  1. Jul 11, 2012 #1
    the higher the energy of the photon, the more powerful it can ionize an atom

    but why then the absorption cross section decreases with the photon energy?
     
  2. jcsd
  3. Jul 11, 2012 #2

    mathman

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    Resonance?
     
  4. Jul 11, 2012 #3
    I'm not aware that it does? Where is this written?

    More photon energy simply means more kinetic energy of the ejected electron, from what I can remember.
     
  5. Jul 11, 2012 #4
    not a resonance
     
  6. Jul 11, 2012 #5

    ZapperZ

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    You need to learn to provide references.

    Zz.
     
  7. Jul 11, 2012 #6
  8. Jul 11, 2012 #7

    ZapperZ

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  9. Jul 11, 2012 #8
    see Cross section
     
  10. Jul 11, 2012 #9

    ZapperZ

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    That is core-level photoemission. It is no longer the same "photoelectric" effect that is characterized by the Einstein equation. Notice the energy of the photon being used. The standard photoemission is done using predominantly visible to UV light that probes the conduction band, not core levels.

    BTW, as someone who has done photoemission spectroscopy extensively, I would use this particular entry in Wikipedia as the poster child why someone should NOT use Wikipedia to learn from.

    Zz.
     
  11. Jul 11, 2012 #10
    i know this

    i have in mind the photoelectric effect of atoms not metals
     
  12. Jul 11, 2012 #11

    ZapperZ

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    Then please look up "photoionization". The topic of this thread is now no longer accurate.

    Zz.
     
  13. Jul 12, 2012 #12

    mathman

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    My recollection is vague, but from what I remeber if the photon energy is just enough to kick the electron out of the atom, the electron is more receptive. As the photon energy gets higher it is less likely to happen. The following may help.

    https://netfiles.uiuc.edu/mragheb/www/NPRE%20402%20ME%20405%20Nuclear%20Power%20Engineering/Gamma%20Rays%20Interactions%20with%20Matter.pdf [Broken]
     
    Last edited by a moderator: May 6, 2017
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