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Polarization of an emitted photon

  1. Dec 27, 2014 #1

    naima

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    Gold Member

    Bonnes fetes de Noel.

    When an excited electron returns to its ground state a photon is emitted.
    Suppose that the electron's spin skip from +1/2 to -1/2 (around z)and that the photon has a momentum parallel to z.
    I suppose that this photon has a circular polarization around z (Is it true?)
    The problem is that there is no spin alone conservation but total angular momentum conservation.
    Knowing all about |e> and |g> what can we calculate about the polarization of the emitted photon?
    Have you links?
     
    Last edited: Dec 27, 2014
  2. jcsd
  3. Dec 27, 2014 #2

    DrClaude

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    Staff: Mentor

    Merci !

    To first order, the spin of the electron is not coupled to the electromagnetic field, so spin-flip doesn't occur during transtions. Look up selection rules.

    You need to consider the total angular momentum of the electron, ##j##. For an emission in which you have ##j = +1/2 \rightarrow j' = -1/2##, that would correspond to a ##\sigma^+## photon, which means that if the photon is travelling along z, it has right-handed circular polarization. A recent discussion on this subject can be found here.
     
  4. Dec 27, 2014 #3

    DrDu

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    Science Advisor

    You should also take in mind that a photon in a momentum eigenstate is not in an eigenstate of photon angular momentum, which are the vector spherical harmonics.
     
  5. Dec 28, 2014 #4

    naima

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    Gold Member

    Thank you
    i read the links and questions will follow.
     
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