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Electrons and Photons

  1. Apr 24, 2010 #1
    Hi, (1st time post)

    When energy is given to an electron and then removed.

    Is there a classical/quantum description that governs which direction the emited photon will take?

    Thanks in advance, If anyone can help answer this one.
  2. jcsd
  3. Apr 24, 2010 #2
    The direction, I believe is governed by statistical analysis. But then its hard to say, because the only way we know what electron a photon hits, and where the photon ends up, is governed by the observer. And until measurements are taken, it's in every single possible place at once. And thus every single direction, and this last bit I'm guessing. But I believe that the direction the photon is emitted, is dependent completely on how the observer influences the statistical analysis.
  4. Apr 25, 2010 #3
    Thanks Simon,

    From what your saying, The electron emits a photon with a certain probability that it will be emitted in the direction of the observer. Assuming the observer can influence the electron and hence the statistical analysis, the probability of the direction the photon takes maybe improved.

    Given the electron has certain properties like spin(up/down), magnetic moment, charge etc. Playing around with any of the properties of an electron may affect the photon directional probabilities.

    Does anyone know of a classical description and/or further resources on specifically electron/photon interaction?
  5. Apr 25, 2010 #4
    Classical descriptions are hard to come by. The thing I did was to watch Richard Feynman's lectures online. Posted by the univeristy of Auckland (sp?). Easiest thing to find them is just googling his name + lectures.
  6. Apr 25, 2010 #5


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    First of all, presumably you are talking about an electron in an atom, or other bound state ... free electrons cannot absorb photons. In the case of a bound state, it depends on whether or not the emission event is spontaneous, or is stimulated by another photon. In the former case, the emission direction is completely random, and therefore unpredictable. In that latter case, the emitted photon will have the same phase and wave-vector (i.e. spatial direction) as the stimulating photon. This is the physical mechanism that makes the light from a laser (Light Amplification by Stimulated Emission or Radiation) coherent (i.e. well-defined phase relationship) and highly collimated (i.e. all going in the same direction).
  7. Apr 28, 2010 #6
    I was interested in laser assisted electron-atom collisions and wasn't clear on how the laser "assists" in the collision.
    for example,
    does the laser carry the electron to the atom or vice-versa? if so how does it do it?
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