When should the nuclear spin be included in atomic spectroscopic notation?

[passingthru]

Forgive me if this has already been discussed. I've been searching and haven't found it. When summing the spin of an atom in the Russell-Saunders coupling scheme, some texts include the spin of an odd nucleon, and some don't. For example, if an atomic energy state is described as ${3}^P_{2}$, this means that the total spin is one, and since $L=1$, $J=S+L=2$. If this is a hydrogen atom, apparently, the spin of the proton is included. Many discussions of this never even bring up the nucleus. When should the spin of an odd nucleon be included?

 

[DrClaude]

When should the spin of an odd nucleon be included?

Never. The spin $S$ is the total electron spin.

Nuclear spin only comes into the quantum number $F$. It is never part of the term symbol itself (the hyperfine state is stated in addition the term symbol, e.g., ²S_1/2 $F=1$).