Estimate the energy due to electron-electron repulsion in helium by calculating the expectation value of the electron-electron interaction in the ground state of para- helium. for this you can ignore the spin-part of the wave function because it is normalized to 1 and it does not enter the expression for the electron-electron inter- action. thus you just need to calculate the expectation value of 1 e2 4160 |r1 – r21 in the state 8 40(ri, r2) = 4100 (rı)t100(r2) = 9,-2(r1+r2)/ao you can choose the polar axis in spherical coordinates to coincide with the direction of r2, so that \rı - r2| = vra + rî – 2r1r2 cos (1 do the integration over 04 first, and in the result distinguish the cases rı < r2 and r1 > r2 before integrating over rı and r2. express the result in units of ry and add it to the energy of the ground state that one gets when neglecting electron-electron interactions, as discussed in the lecture. compare the total with the experimental value for the ground-state energy of -79ev.