Underlying physics

The underlying physics that elucidates why the electron-electron might be influenced by the spin state involves multi-electron states, and that is something we haven't really gone over. The simplest case is two electrons, but even that has some interesting subtleties. It is not just what states are occupied that matters. I'll try to do a post on that later, but if anyone has some experience and interest in two electron states, feel free to do a post. I believe that the influence of the spin state on the e-e interaction has to do with the correlations built into the multi-electron state via symmetrization.