Algebraic vibrational description of the symmetric isotopologues of CO2: (CO2)-C-13-O-16, (CO2)-C-12-O-18 and (CO2)-C-12-O-17

We present a polyad-conserving local model applied to the vibrational excitations of symmetric isotopologues of carbon dioxide. The description is carried out in the framework of local internal coordinates where the stretching degrees of freedom are modeled with Morse oscillators while for the bending modes the algebraic U(3) model is introduced. Three isotopologues are considered, namely (CO2)-C-13-O-16, (CO2)-C-12-O-18 and (CO2)-C-12-O-17 in their electronic ground states. In all cases the most extensive experimental dataset of vibrational energies were taken into account. For the three isotopologues a Hamiltonian with interactions up to sixth order involving 16 parameters was considered. The description of the isotopologue & nbsp;(CO2)-C-13-O-16 involved 110 experimental energies with a rms = 0.06 cm(-1). On the other hand, for the isotopologue (CO2)-C-12-O-18, only 42 experimental energies were available and a rms = 0.05 cm(-1) was obtained with 15 parameters. For the isotopologue (CO2)-C-12-O-17, considering 28 experimental energy terms a rms = 0.17 cm(-1) was obtained. In addition, as a consequence of the normal mode behavior of these molecules, alternative polyad schemes were explored.