O 1s -> sigma* resonance in O-2: Inadequacy of only two exchange-split components

The O 1s --> sigma* transition below the O K-edge in O-2 has been investigated by absorption, constant ionic state ( CIS) experiments, and extensive configuration interaction calculations. CIS scans of the three lowest-lying final states reached in resonant Auger decay provide a wealth of information on energy range, symmetry, and spin multiplicity of the intermediate states with sigma* character. We conclude that the identification of only two exchange-split components is inadequate because a complex manifold of states with sigma* character exists with no unique energy difference between related states.