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I have question on Helium with one electron in it's ground state orbital 1s and the other in the 2s orbital. We have S=1 states reffering to the spin symmetric triplet state and S=0 reffering to the spin antisymmetric singlet state, due to quantum effects of the electron-electron interactions we find that the energy of S=1 state and S=0 states are split by the direct and exchange components of the energy correction.

We find that S=1 states, where the spins are parallel, have lower energies than S=0 states - not sure of the physical interpretation of this - I'm guessing it's just because it's energetically favourable to have parallel spins further apart than having opposing spins in the same orbital.

Anyway, the S=1 states and S=0 states have very different lifetimes but I'm not sure what is meant by 'lifetimes' and why the lifetimes are different?

Thanks for any help,

SK

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# Lifetimes of He S=1,0 states

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