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Homework Help: Angular momentum during Annihilation of Positron-electron

  1. Jul 3, 2012 #1
    1. During the annihilation of positron and electron AT REST, two photons are generally created at opposite direction - angle between them being 180 degres.

    However, an electron that is orbiting around an atom can sometimes react with a positron. The orbital electron in that case has therefore a momentum, hence not at rest, and the resulting photons are therefore emerging at an angle that is NOT 180 degrees - See the file attached!

    The momentum of the electron around the atom can be rougly obtained with the equation of the quantized angular momentum

    2. L = p×r = nh/2pi

    3.I am trying to get the maximum angle θ that appears when the vector of the momentum of the electron (black) is perpendicular to the horizontal line (red)

    Since writing the equation here could be quite fastidious to understand, I attached a written version of my equations a a .gif file

    Thank you very much,


    ps: I am absolutely new to this forum so please tell me if I need to add more details or wrote something wrong.

    Attached Files:

  2. jcsd
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