I think that the normal Zeeman effect is experimentally observed only when we can neglect the spin i.e. if we consider a spin-singlet state with total spin $S=0$. Since in the hydrogen atom there is only one electron, we cannot observe the normal Zeeman effect in the Hydrogen atom. Am I right?
1 Answer
Yes, you are correct. The "normal" Zeeman effect refers to the splitting of spectral lines into an odd number of components, which could occur for integral orbital angular momentum (e.g., the $M_L = -1, 0, +1$ levels of a $p$ orbital). When there is a single unpaired electron spin, $S=1/2$, so an even number of spectral lines results and this is called the "anomalous" Zeeman effect. In the hydrogen atom, the unpaired electron spin means that a "normal" Zeeman effect is not observed.