# Talk:Semiclassical theory of helium atom

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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)\[ \mathbf{L} = \frac{1}{2}m\mathbf{v}^2+\frac{Ze^2}{r}+\frac{Ze}{c}\left[ \mathbf{v}\cdot\left( \frac{\mu\times \mathbf{r}}{r^3}\right)\right]\]