Matrix for 2 interacting electrons.

I have had second thoughts about discarding the two states that had spin 1. In retrospect, I think it would be better for illustrating and understanding the essential physics if we kept them and worked with a 6x6 matrix. Over the weekend please put in the off-diagonal matrix elements, representing coupling between states connected by a single "hop".  Come to class Monday with your own 6x6 Matrix made of \(E_1\), U and I.