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Ground state

  1. Feb 6, 2014 #1
    Just curious: if an electron absorbs a photon of energy, it is in an excited state. The electron may go to a lower energy state (but NOT the ground state). Can a photon (of higher wavelength than absorbed) be emitted still?

    I don't quite see the importance of the electron having to go to the ground state in this case...
  2. jcsd
  3. Feb 6, 2014 #2


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    Staff: Mentor

    Do you mean a longer wavelength, or a higher frequency? A "higher wavelength" doesn't make sense.

    In any case, an electron can exist above the ground state, absorb a photon, and then fall to a lower state than what it was occupying emitting a photon of higher frequency than what it absorbed in the process.
  4. Feb 7, 2014 #3
    Isn't a higher wavelength proportional to lower energy? How would it emit a higher energy photon (i.e. higher frequency) than what it absorbed?

    So to confirm, a photon can still be emitted despite the electron not decaying to its ground state, just any state lower than its excited state, correct?
  5. Feb 7, 2014 #4


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    A photon can be emitted if the system goes from a higher energy state to a lower energy state (not necessarily the ground state), and if it abides by the selection rule.

    Example: the Balmer lines in H atom.

    Last edited: Feb 7, 2014
  6. Feb 7, 2014 #5


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    Staff: Mentor

    The extra energy required to emit a photon of higher frequency than the electron absorbs comes from the extra energy it already had by being in a state above the ground state.

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