Theoretical study of the electronic states of CO2++

Three-dimensional potential energy functions (PEFs) have been generated for the X-3 Sigma(g)(-), a(1) Delta(g), and b(1) Sigma(g)(+) states of CO2++ using the internally contracted multireference configuration interaction approach. Analytic forms of the PEFs were employed in calculations of the vibrational energy levels, vibrational wavefunctions and Franck-Condon factors for the hypothetical direct ionization process CO2 --> CO2++ + 2e. For the (1) Delta(g) state the Renner-Teller problem has been solved and the pattern of the bending levels analysed. The collinear charge separation path yielding CO+ + O+ has been calculated for 14 electronic states. The electronic ground state of CO2++ was found to have a barrier height of 1.4 eV, in good agreement with the experimentally detected onset of this charge separation process. The shapes of the close-lying potential energy functions indicate that for energies higher than about 4 eV above the electronic ground state, dissociation processes from these states will be accompanied by complicated coupling effects.