Question

For the 2P_3/2 → 2S_1/2 transition of an alkali atom, sketch the splitting of the energy levels and the resulting Zeeman spectrum for atoms in a weak external magnetic field (Express your results in terms of the frequency v₀ of the transition, in the absence of an applied magnetic field)

Answer 1

Lande’ g-factor is 

g = 1 + j(j + 1) + s(s + 1) − l(l + 1)/2 j(j + 1) 

For the term 2P_3/2,l = 1, J = 3/2 ,s = 1/2 and g = 4/3 

For 2S_1/2,l = 0, j = 1/2 ,s = 1/2 and g = 2

The splitting of levels as in sodium is shown in Fig. 2.5. Transitions take place with the selection rule 

ΔM = 0, ±1.