Ok thanks, I am using Shriver and Atkins 5th edition Inorganic Chemistry textbook and they have a line from O2s to the 4 sigma orbital. One of the problems I have had searching the web is that none of the diagrams seem to be consistent with each other.
I am still a bit confused though as to which are the bonding and anti bonding molecular orbitals, I get the MO diagrams of things like O2 and F2 and but can't get my head around this one. I think I am getting confused with the interactions between the s and pz orbitals and where the lines for the mixing of these orbitals should direct to.