# Homework Help: Atomic transition - What does this notation mean?

1. Aug 12, 2006

### octol

Hello all, I've been reading about laser cooling, and when they speak of tuning the laser to a atomic transition, they write this (for example) as
"The laser cooling was performed on the $$D_2$$ transition ($$3S_{1/2} \rightarrow 3 P_{3/2}$$)".

But what do they mean by that notation? I'm clueless as what it is supposed to mean as it doesn't look like the spectroscopic notation (i.e the number 3 is NOT in superscript).
Best regards,
Jon

2. Aug 12, 2006

### Astronuc

Staff Emeritus
I believe that the 3 is the principal quantum number, S and P are related to the suborbtial or azimuthal quantum number, and 1/2 and 3/2 are (IIRC) the total electronic angular quantum momentum numbers which parameterize the total angular momentum of a given electron, by combining its orbital angular momentum and its intrinsic angular momentum (i.e., its spin).

Has one studied the quantum numbers of atomic electrons?

3. Aug 12, 2006

### octol

ok so the
$$3 S_{1/2} \rightarrow 3 P_{3/2}$$
means the same as for a normal transition, except that this is in the case of a composite system? i.e the transition is L=0 to L=1 and J=1/2 to J=3/2.

What is then meant by $$D_2$$? And how does this relate to the above?