Global fittings of the vibrational-rotational line positions of the 16O12C17O and 16O12C18O isotopic species of carbon dioxide

The effective operator approach is applied to the calculation of the line positions of two isotopic species, (OCO)-O-16-C-12-O-17 and (OCO)-O-16-C-12-O-18 of the carbon dioxide molecule. More than 6600 observed line positions of 72 bands of (OCO)-O-16-C-12-O-18 selected from the literature have been used to derive 73 parameters of a reduced effective Hamiltonian globally describing all vibration-rotation energy levels in the ground electronic state. The dimensionless weighted standard deviation of the fit is 2.15 and the RMS (root-mean-square) deviation is 0.00134 cm(-1). In the case of (OCO)-O-16-C-12-O-17 about 1800 line positions of 30 bands also taken from the literature have been used to derive 45 parameters of a reduced effective Hamiltonian. The dimensionless weighted standard deviation of the fit in this case is 1.63 and the RMS deviation is 0.00129 cm(-1). The quality of the fittings and the extrapolation properties of the fitted parameters are discussed. A comparison of calculated line positions with those provided by the HITRAN and GEISA databases is given. (C) 2001 Elstvier Science.