A configuration interaction study of the (O₂)₂ DIMER

The ground and excited states complex between two oxygen molecules has been studied by configuration interaction (CI) calculations, scanning the intermolecular distance in D_2h symmetry of collision. The calculations give a good explanation of antiferromagnetic character of the dimer and of exchange splitting in its lowest singlet, triplet and quintet multiplet states. The intermolecular potentials for 9 excited states of the dimer are also presented. The results are in good agreement with recent perturbation theory calculations. The electric quadrupole moments for the five lowest states of different symmetry are tabulated at various intermolecular separations. They all show extremum behavior in the vicinity of the equilibria. Highly excited excimers of zwitter-ionic character are predicted near the ionization threshold with dissociation energies of the order of 1.5-1.8 eV. The corresponding excimer emission is predicted in the 130 nm UV region.