Zeeman splitting of a spectral line in the presence of a strong magnetic field as compared to that of a magnetic field of intermediate strength

Question

Will the number of spectral lines into which a spectral line will split due to an electronic transition from a P state with spin=1/2 to a S state with spin=1/2 be more in the presence of a strong magnetic field as compared to a magnetic field of intermediate strength ?

I am aware that using the selection rules $\Delta m_{j} = 0,+1,-1$ ($\ m_j=0 $ to $\ m_j=0$ transition only when $\Delta J=0 $ ; where $\ j = \mid l-s \mid to \mid l+s \mid$) one can calculate the allowed transitions. But what i am unable to understand is that how the magnetic field strength affects the above mentioned selection rules governing the number of lines into which a spectral line is split.

It would be very helpful if the explanation is based on the particular case which i have mentioned above.

Thanks in advance.

Answer 1

The total number of lines corresponding to Zeeman splitting will not change as $B$ increases because it is governed only by the number of different states that the spin has, which for an electron with $s = 1/2$ is 2 (-1/2 and +1/2). However, the energy separation of the different angular momentum states does change when $B$ increases. Particularly when the magnetic interactions become comparable to orbital energies, the electronic structure changes completely.