Theoretical study of the electronic states of

Three-dimensional potential energy functions (PEFs) have been generated for the X , a , and b states of 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 . For the state the Renner-Teller problem has been solved and the pattern of the bending levels analysed. The collinear charge separation path yielding has been calculated for 14 electronic states. The electronic ground state of 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.