In the presence of an external magnetic field (normal Zeeman effect), the transition ${ }^{1} \mathrm{D}_{2} \rightarrow{ }^{1} \mathrm{P}_{1}$ splits into
(a)9 lines
(b)8 lines
(c)7 lines
(d)6 lines
Answer
Answer: A ✓ checked by 4AB · confidence low
Explanation
M_J = 2 gives 5 sublevels and M_J = 1 gives 3. ΔM_J = 0, ±1 allows 9 component transitions; in the normal Zeeman effect they fall at only 3 distinct frequencies. The key counts components: 9 (a).