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How are room temperature photons produced?

  1. Mar 12, 2005 #1
    I am trying to understand the mechanisms for room temperature thermal radiation which is in the far infrared range. I have been told that photon emission in the infrared range occurs as a result of a reduction in the vibrational energy of molecules. Is this the same as phonons? How does a phonon actually get converted to a photon?
     
  2. jcsd
  3. Mar 12, 2005 #2

    dextercioby

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    Well,phonons & photons are different animals.Sure,they're bosons,but they are different particles.Thermal emission of radiation occurs when an electron makes different quantum transitions between various energy levels in molecules...The so-called "thermal photons" (in IR & microwave) are emitted or absorbed.

    Daniel.

    EDIT:Because the other 2 threads were deleted,i'll say again to check both books by Davydov (hopefully they're both translated from Russian-->English,the QM one definitely is).
     
    Last edited: Mar 12, 2005
  4. Mar 12, 2005 #3
    "Thermal emission of radiation occurs when an electron makes different quantum transitions between various energy levels in molecules..."

    How is this so different from how photons are produced?
     
  5. Mar 12, 2005 #4

    dextercioby

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    "Radiation" means photons.Wasn't it obvious from the context??

    Daniel.
     
  6. Sep 8, 2011 #5
    I will clarify my question. A phonon is a bundle of energy that propagates between atoms or molecules within a material i.e. a lattice vibration. Room temperature photons are generated by changes in the rotational or vibrational energy of molecules. They are not created by atomic transistions which produce visible or UV light. So my real question is how/why does a propagating phonon get absorbed by a molecule and converted to light?
     
  7. Sep 8, 2011 #6

    Bill_K

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    You're correct, black body radiation is not created by atomic transitions. It does not necessarily involve molecular vibrations either. It's caused by the thermal collisions between atoms.

    Atoms are polarizable. Two atoms brought close together will distort each other's orbitals. The effect is adiabatic, i.e. much lower in frequency than the frequencies associated with atomic energy levels. And since atoms are made up of charges, time-varying distortions produce electromagnetic radiation. The net result is that energy is transferred from thermal motion (phonons) to electromagnetic waves (photons).
     
  8. Sep 8, 2011 #7

    Claude Bile

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    The 6.5 year response time from the OP must be some kind of record. Can we expect McSteven's reply to be around March 2018? :smile:.

    Claude.
     
  9. Sep 8, 2011 #8

    Chronos

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    At least we know it wasn't a homework question.
     
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