# Talk:Semiclassical theory of helium atom

I see the article neglects the causing spin-orbit interaction very strong magnetic dipole magnetic moment of electron ($$\mu$$): Lorentz force proportional to its velocity ($$\mathbf{v}$$) and charge of the nucleus ($$Ze$$). This force perpendicular to velocity makes circular orbits unstable. For example here is the basic Lagrangian for single electron - the last term contains this additional Lorentz force (en.wikipedia.org/wiki/Free-fall_atomic_model)$\mathbf{L} = \frac{1}{2}m\mathbf{v}^2+\frac{Ze^2}{r}+\frac{Ze}{c}\left[ \mathbf{v}\cdot\left( \frac{\mu\times \mathbf{r}}{r^3}\right)\right]$