# Angular momentum

1. May 5, 2010

### luxiaolei

Hi,all

I found myself so hard to turly understand (spin)angular moment, like spin parallel, triplet state, z component of angular moment etc...always mixed them up and confuse myself.
Anyone can help me with understanding these and clarify them would be really helpful.

Q1: Sz spin in z direction in the real space?

Q2:trplet sate has S=1, why one of them is of the form (1/root(2)) (|up down> + |down up>)? its probability or anythingelse? ( I though before, triplet states are parallel and singlet is antiparallel)

2. May 5, 2010

### stephenhky

Q1: im not sure if i understand your question, but Sz means the spin in z-direction in real-space. but of course, it is up to the definition of z-axis in your system.

Q2: You can operate (S_1+S_2)^2 on the state you have to see if it gives an eigenvalue 1*(1+1). (This is actually a tricky quantum mechanics homework problem. People often forgot how to do it when they have taken the course too many years ago.)

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