The nu1 + 5nu3 Dyad of 12CO2 and 13CO2

MARVEL analysis of high-resolution rovibrational spectra of 13 C 16 O 2

A set of empirical rovibrational energy levels, obtained through the MARVEL (measured active rotational-vibrational energy levels) procedure, is presented for the  13 C  16 O  2 isotopologue of carbon dioxide. This procedure begins with the collection and analysis of experimental rovibrational transitions from the literature, allowing for a comprehensive review of the literature on the high-resolution spectroscopy of  13 C  16 O  2 , which is also presented. A total of 60 sources out of more than 750 checked provided 14,101 uniquely measured and assigned rovibrational transitions in the wavenumber range of 579-13,735 cm  - 1 . This is followed by a weighted least-squares refinement yielding the energy levels of the states involved in the measured transitions. Altogether 6318 empirical rovibrational energies have been determined for  13 C  16 O  2 . Finally, estimates have been given for the uncertainties of the empirical energies, based on the experimental uncertainties of the transitions. The detailed analysis of the lines and the spectroscopic network built from them, as well as the uncertainty estimates, all serve to pinpoint possible errors in the experimental data, such as typos, misassignment of quantum numbers, and misidentifications. Errors found in the literature data were corrected before including them in the final MARVEL dataset and analysis.

A Spectroscopic Description of Asymmetric Isotopologues of CO2

A polyad-conserving algebraic model applied to vibrational excitations of asymmetric isotopologues of CO2 is presented. First, the problem of vibrational excitations is studied by taking into account only the minimum subspace of states to characterize the Fermi interaction. This analysis allows an estimation of the force constants as well as the feasibility of describing the system in a local mode scheme, in terms of SU(2) operators associated with Morse ladder operators for the stretches. This description together with the algebraic U(3) for the bends establishes the dynamical group SU1(2) × U(3) × SU2(2) for a series of isotopologues. Six isotopologues are considered, namely, 16O12C18O, 16O12C17O, 16O13C18O, 16O13C17O, 17O13C18O, and 17O12C18O in their electronic ground states. For isotopologues 16O12C18O, 16O12C17O, 17O12C18O, and 16O13C18O, the vibrational description was carried out using a Hamiltonian involving 14 parameters. For this series of isotopologues with a number of energy terms 90, 57, 42, and 40, the deviations obtained were rms = 0.15, 0.10, 0.06, and 0.07 cm-1, respectively. For 16O13C17O, with 28 experimental energies and involving 13 parameters, the deviation was rms = 0.05 cm-1, while for 17O13C18O, a different strategy was proposed since only 12 experimental energy levels. In all cases, the polyad scheme P212 = 2(ν1 + ν3) + ν2 was considered. In addition, a new criterion of locality/normality degree is proposed, embracing the case of molecules with normal mode behavior, in particular, the isotopologues of CO2.

Spectroscopy and Intensity Measurements of the 3nu(1)+3nu(3) Tetrad of (12)CO(2) and (13)CO(2)

Three of the four components of the 3nu(1)+3nu(3) tetrad of (12)C(16)O(2) and (13)C(16)O(2), labeled 30031, 30032, and 30033 in HITRAN notation, have been observed by intracavity laser absorption spectroscopy in the 10 450- to 11 000-cm(-1) region. The rotational analysis has yielded the rovibrational parameters of the vibrational states. The experimental values are found to be in very good agreement with the rovibrational energies recently predicted from variational calculations and reduced effective Hamiltonians. The absolute band intensity of these extremely weak transitions have been measured. The study of the relative intensities within the 3nu(1)+3nu(3) tetrad suggests that part of the oscillator strength is carried by the (22(0)3) state. Copyright 2001 Academic Press.

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.