To demonstrate some influences in that causes the splitting of emission lines of atomic spectra, sodium lamp where you can find the bright doublet which is responsible for the bright yellow light can be used. The transition which gives rise to the doublet is from 3p to 3s level, level the same as hydrogen atom. A good example of dependence atomic energy levels on angular momentum is the fact that the 3s (orbital quantum number = 0 ) is lower than 3p (1=1).
How photon theory of lights account for atomic spectra:
Orbitals in third principal energy level:
Orbitals present in fifth principal energy level: