Hello, I have a small question about coupling of angular momenta.

When you have JÂ² with J = J1 + J2; you change it to the form (dropping the hbar in all equations):

jÂ² = j

now it's these j

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

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

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 :)

When you have JÂ² with J = J1 + J2; you change it to the form (dropping the hbar in all equations):

jÂ² = j

_{1}Â² + j_{2}Â² + j_{1-}j_{2+}+ j_{1+}j_{2-}+ 2j_{1z}j_{2z}now it's these j

_{1-}j_{2+}I have a problem with.Let's say you use it on |1/2;-1/2>. The answer is âˆš[j1(j1+1) - m1(m1-1)] . âˆš[j2(j2+1) - m2(m2 + 1)]

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

**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 :)

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