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Coupling of angular momenta

  1. Dec 23, 2013 #1
    Hello, I have a small question about coupling of angular momenta.

    When you have J² with J = J1 + J2; you change it to the form (dropping the hbar in all equations):

    j² = j1² + j2² + j1-j2+ + j1+j2- + 2j1zj2z

    now it's these j1-j2+ I have a problem with.

    Let's say you use it on |1/2;-1/2>. The answer is √[j1(j1+1) - m1(m1-1)] . √[j2(j2+1) - m2(m2 + 1)]

    Ok, no problem. But apperently, the answer is: √[1/2(1/2+1) - 1/2(1/2-1)] . √ [ 1/2(1/2 + 1) - (-1/2)(-1/2 + 1)]

    So the j2 = 1/2 and not -1/2 and I don't know why...
    Unless it is because the angular momenta is quantisised from 0, 1, ...? Could that be it?
    and what if you a further j- on the new basecomponent?

    edit: nvm, found out :)
    Last edited: Dec 23, 2013
  2. jcsd
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