Potential energy curves for twelve valence states of O-2 are calculate
d with fully linked renormalized Feynman diagrams which dissociate pro
perly. Compared with experiment, average errors of spectroscopic const
ants are: 18 kJ mol(-1) for D-e, 2 . 1 pm for R(e), 81 cm(-1) for omeg
a(e), 15 kJ mol(-1) for T-e, and 16 kJ mol(-1) for the sum of asymptot
ic atomic excitation energies.