Spin-orbit interaction
= Spin-orbit interaction
{title2=$H_{\rm so}\propto\mathbf L\cdot\mathbf S$}
{wiki=Spin–orbit_interaction}
= Spin-orbit coupling
{synonym}
The spin-orbit interaction couples <orbital angular momentum> to <spin>. In <chemical atoms> it helps determine <fine structure> and the coupling scale that separates <weak-field Zeeman splitting> from the <Paschen-Back effect>.