Theoretical assignments of the low-lying electronic states of carbon dioxide

Extensive configuration interaction calculations (1000 to 1500 determinants) have been carried out for the six low-lying valence states of carbon dioxide in order to provide reliable assignments for the transitions to these states. In addition, Hartree-Fock calculations were performed on the lowest five (singlet and triplet) Rydberg states and the ²Π_g state of the positive ion. These results yield an accurate description of the excited states of carbon dioxide and provide for definitive assignments of the transitions observed by optical and electron impact studies (for the five states known experimentally, the calculations agree to within 0.2 eV of the experimental transition energies).