 Alfred Landé

Alfred Landé organized the magnetic response of coupled atomic angular momenta. The Landé g-factor relates a magnetic energy shift to the projection of total angular momentum, accounting for both orbital angular momentum and spin. For LS coupling, $g_J=1+[J(J+1)+S(S+1)-L(L+1)]/[2J(J+1)]$ when $J\ne 0$, neglecting the small correction to the electron spin g-factor. For $L=0$ and $J=S=1/2$, it gives $g_J=2$. Different atomic terms therefore split differently in a weak magnetic field.^[ref]

A physicist.^[ref]