Hydrogen in Electric and Magnetic Fields

Hydrogen levels n = 1..4 split under external fields. The primary scene is the physical term diagram, each Rydberg level fanning into sublevels as the magnetic (Zeeman, dE = mu_B B m_l) and electric (linear Stark for n >= 2) fields ramp, with the chosen transition drawn; beside it the synthetic spectrum shows the line splitting a spectrometer records (a normal-Zeeman triplet, a Stark multiplet), zoomed onto the multiplet. The ground state shows the textbook result: no first-order Stark shift (it has no permanent dipole), only a tiny negative quadratic one, while excited levels with degenerate l mix and split linearly in the field. Ramp B and the electric field and pick a transition to watch the normal-Zeeman triplet and the Stark multiplet form.