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Homework Help: Adding angular momenta

  1. Jun 19, 2008 #1
    1. The problem statement, all variables and given/known data
    An electron with spin up is in the state |n=5, l=1, s=0> of the hydrogen atom. If you could measure the angular momentum of the electron alone, what values might you get and what is the probability of each.

    2. Relevant equations
    This problem involves adding angular momenta.
    l-s,...,|l-s|= ?

    3. The attempt at a solution
    spin up means the spin is +1/2
    The state ket for the electron is |l=1,s=0>|1/2, 1/2>
    1+ 1/2= 3/2
    1 - 1/2= 1/2
    These are the two possible values for the angular momentum of the electron, so it must be something like
    |1,0>|1/2,1/2>= ____|3/2,1/2>+ _____|1/2,1/2>
    I don't know how to find the coefficients which (squared) would give the probabilities. Laddering? But where do I start?
  2. jcsd
  3. Jun 21, 2008 #2
    Actually I have to find the possible angular momenta squared and their probabilities but it amounts to the same thing.
  4. Jun 21, 2008 #3
    i think i got it.
  5. Jun 22, 2008 #4
    I got to thinking about this topic and came up with some problems of my own, so I started a thread in Quantum Physics under the heading "Change of Basis for Spin States". Just thought I'd point it out in case you're interested.
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