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B Electron moving to lower energy state

  1. Feb 13, 2017 #1
    When an electron moves to lower energy state it emits a photon, now if a photon is absorbed by an electron does the electron move back to the higher energy state. (I don't think that 'energy state' is the right term) If so how hard is it to put the photon into the electron? I assume that it not an everyday occurrence as then all electron would be endless moving up.
     
  2. jcsd
  3. Feb 13, 2017 #2

    Drakkith

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    If the photon has the right amount of energy, equal to the difference in energy between the two levels, then yes, the electron can be excited into the higher energy level.

    It is very easy to do. This isn't a problem because the vast majority of the time the electron quickly falls back down from its excited state, releasing that energy either as light or as heat. Also, every excitation would require light of a different wavelength and the chances of the atom absorbing light with exactly the right energy in exactly the right order at exactly the right time is very small.

    Also note that there are essentially no single atoms roaming about around you. Almost all atoms are locked into molecules of gas, liquids, or solids. Molecules have several more ways to absorb and release energy other than electronic transitions, and their electronic transitions are often complex, multi-state processes.
     
  4. Feb 13, 2017 #3
    Atoms are constantly emitting and absorbing photons. The electrons don't constantly go up in energy because they are typically emitting photons as fast as they are absorbed.

    You probably have some argon atoms around you.
     
  5. Feb 13, 2017 #4

    Drakkith

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    Ah yes, I forgot about the argon in the atmosphere.
     
  6. Feb 13, 2017 #5

    m k

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    Can low energy photons make an exitation exception if they are ver very close and all their energies point to favourable direction?
     
  7. Feb 13, 2017 #6
    Can you rephrase that, m k? I can't understand you.
     
  8. Feb 13, 2017 #7

    Drakkith

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    As far as I know, absorption of two photons of lower energy at exactly the same time is possible, but extremely unlikely. Also, energy is not a vector, it does not have a direction. Perhaps you mean the electromagnetic field vectors, but those are not really related to the energy levels of an atom.
     
  9. Feb 13, 2017 #8

    DrClaude

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    In other words, you need intense lasers to get significant rates of multi-photon absorption.
     
  10. Feb 13, 2017 #9

    jtbell

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    It occurs continuously in the outer layers of the Sun's atmosphere. This is what creates the dark Fraunhofer lines in the solar spectrum.
     
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