In case of the strong-field Zeeman effect, when the applied field is strong enough, so that the orbital and spin angular momenta decouple, the good quantum numbers are now n, l, m l, and m s. Here, L z and S z are conserved, so the perturbation Hamiltonian is given by- V ^ ^ = e B ( L z + 2 S z ) / 2 m assuming the magnetic field to be along the z -direction. So, V ^ ^ = e B ( m ℓ ℓ + 2 m s ) / 2 m For each value of m ℓ, there are two possible values of m s, ± ± 1 / 2 .