12C16O2 in Emission in the 4.5-µm Region: Transitions v1vl2v3 --> v1vl2(v3-1) with (2v1 + v2) = 6 Occurring between Highly Excited Vibrational States

Variational Calculations of Rovibrational Energies for CO(2)

Vibrational-rotational energy levels for the CO(2) molecule are computed variationally using an empirical potential energy surface previously determined. The calculations are carried out using a set of generalized internal coordinates properly optimized to describe the internuclear motions of the molecule. The rovibrational energies are used to determine the vibrational terms G(v) and the inertia constants B(v) for states with l = 0 to l = 6, and the values of these molecular constants are compared to those derived from the observed spectra. There exists excellent agreement between the calculated and the observed constants, which confirms the good quality of the potential energy surface used. Copyright 2001 Academic Press.

13C(16)O(2): Global Treatment of Vibrational-Rotational Spectra and First Observation of the 2nu(1) + 5nu(3) and nu(1) + 2nu(2) + 5nu(3) Absorption Bands

The effective operator approach is applied to the calculation of both line positions and line intensities of the (13)C(16)O(2) molecule. About 11 000 observed line positions of (13)C(16)O(2) selected from the literature have been used to derive 84 parameters of a reduced effective Hamiltonian globally describing all known vibrational-rotational energy levels in the ground electronic state. The standard deviation of the fit is 0.0015 cm(-1). The eigenfunctions of this effective Hamiltonian have then been used in fittings of parameters of an effective dipole-moment operator to more than 600 observed line intensities of the cold and hot bands covering the nu(2) and 3nu(2) regions. The standard deviations of the fits are 3.2 and 12.0% for these regions, respectively. The quality of the fittings and the extrapolation properties of the fitted parameters are discussed. A comparison of calculated line parameters with those provided by the HITRAN database is given. Finally, the first observations of the 2nu(1) + 5nu(3) and nu(1) + 2nu(2) + 5nu(3) absorption bands by means of photoacoustic spectroscopy (PAS) is presented. The deviations of predicted line positions from observed ones is found to be less than 0.1 cm(-1), and most of them lie within the experimental accuracy (0.007 cm(-1)) once the observed line positions are included in the global fit. Copyright 2000 Academic Press.