# Quation about term symbols: N atom

1. May 20, 2012

### Mr Boom

So the term symbol for the nitrogen atom is 4S3/2

This means L=0, S=3/2, hence J=3/2. My question is that if S=3/2 than this is a quartet, meaning there are four levels, yet I only ever see one state listed on energy diagrams? What gives? Obviously, I'm still trying to learn term symbols Are there four levels and all of the atoms assume the lowers level? So you can't do absorption, for example, on the three higher levels because they won't be populated?

2. May 21, 2012

### DrDu

Btw, this question is more apt for the atomic physics forum.
To your question: As long as there is no magnetic field the four states with S=3/2 or J=3/2 are degenerate. In a magnetic field you will observe the splitting i.e. the Zeeman effect.

3. May 21, 2012

### Mr Boom

OK, that makes sense. I think my confusion was that I was comparing the nitrogen and oxygen term symbols with known transition lines and for oxygen (triplet P) there are three close P line corresponding to different J values. These three lines don't represent the triplet of the ground state but rather the ground state and two other states. Correct?

Also, when I have a molecular term symbol, say for N2(A), I have a triplet sigma. does the same thing apply? The reason I ask is because I'm looking at a paper that talks about the different linestrengths (looking at N2(A)->N2(B) (trip pi)) when going from one to another (P11 being stronger than P12, etc). If they are truly degenerate, than why do they have different linestrengths and how would you even know?

4. May 21, 2012

### Staff: Mentor

And it has been moved accordingly.