Discussion:
The Energy of Spin-Orbit Coupling
Q: Show that the energy of interaction is proportional to the scalar product s·l.?
The energy of a magnetic moment μ in a magnetic field B is equal to their scalar product μ.B. If the magnetic field arises from the orbital angular momentum of the electron, it is proportional to the l: if the magnetic moment μ is that of the electron spin, then it is proportional to s. It then follows that the energy of the interaction is proportion to the scalar product s-l.