Interactions of Rydberg and valence states in CO 2

Abstract

The electronically excited singlet and triplet states of CO 2 lying below 11.4 eV have been investigated by ab initio MCSCF calculations. It has been found that the valence excited states with the electronic configuration (1π 3 g2p2π 1 u form sharp avoided crossings along the symmetric stretching coordinate with the Rydberg states of the same symmetry resulting from the electronic configuration (1π 3 g3p3π 1 u). Hence, the Rydberg states can dissociate into the lowest valence asymptotes O( 3P, 1D) + CO(X 1Σ +), in accordance with experimental findings. In addition, the photodissociation of CO 2 is complicated by the fact that the valence singlet and triplet states 1,3Σ − u and 1,3Δ u form conical intersections with the diffuse 1,3Π g states in the Franck-Condon region of the absorption spectrum.