The Sodium emission spectrum has 2 bright yellow lines called the Na-D lines. Superficially I understand the cause; there's spin-orbit coupling and the 3p orbital is split into 3p(3/2) and 3p(1/2).
But I don't understand why those numbers (3/2 and 1/2)?
Are these the total angular momentum values or the orbital angular momentum values?
And how does one work them out?