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How Does the ΔS = 0 Selection Rule Arise?

  1. Aug 8, 2012 #1
    Exactly what the title says.

    I know that there exists a selection rule that ΔS=0, but I cannot find a quantum mechanical explanation for these transitions being forbidden. I know that it has something to do with the electric dipole, but I have not been able to find anything explicit.

    In reference to my earlier thread, I want to state mathematically why singlet->triplet transitions are forbidden and then use spin orbit coupling to show why these transitions still happen (though with less probability) due to singlet/triplet mixing.

    My best clue so far:

    Anything would be excellent, so I can get a better starting point. A section from a book would be preferable though so that I could cite it. I've looked in Sakurai, Blinder, and Atkins/Friedman so far with no luck.

    Thanks again!
  2. jcsd
  3. Aug 8, 2012 #2


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  4. Aug 8, 2012 #3


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    Have a look how the spin couples to the EM field in the non-relativistic limit:
    Try to estimate the relation of a d*E term (responsible for electric dipole transitions) to the Stern Gerlach term e.g. for visible light.
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