Presets
Line type
Viewing direction
Live readout
What to try
1. Normal triplet: three equally spaced lines, shift of mu_B B each. 2. Switch to the sodium D2 line: six lines at 1/3, 1, 5/3 of the Larmor unit. 3. Look along the field: the central pi lines vanish and only the sigma pair remains.
Model checks
The science
In a magnetic field B each level with total angular momentum J splits into 2J+1 sublevels with energy shift dE = g m mu_B B, where the Lande factor is g = 1 + [J(J+1) + S(S+1) - L(L+1)] / [2 J(J+1)]. A photon line shifts by d(lambda) = -(lambda0^2 / hc) dE. Dipole selection rules allow dm = 0 (pi, polarized along B) and dm = +/-1 (sigma, circular).
Relative intensities for 2P3/2 to 2S1/2 come from squared Clebsch-Gordan coefficients: sigma outer pair 1, pi pair 2/3, inner sigma pair 1/3. Seen along B the pi lines are absent; seen across B they are linearly polarized along the field. The sodium D2 pattern spans lines at +/-1/3, +/-1 and +/-5/3 of mu_B B.
Honest simplifications: weak-field (Zeeman) regime only, so no Paschen-Back transition; no hyperfine structure; line broadening is a display choice; the normal triplet is shown with equal intensities of 1 : 1 : 1 weighted by the squared coefficients for J=1 to J=0.