Application of the Effective Operator Approach to the Calculation of 12C16O2 Line Intensities

The effective operator approach has been applied to the calculation of line intensities of 12C16O2. Using the eigenfunctions of our reduced effective Hamiltonian (1992, J. Mol. Spectrosc. 156, 48-64) the experimental line intensities of cold and hot bands lying in the regions of 15, 10, and 5 µm have been fitted to parameters of the corresponding effective dipole moment matrix elements. The quality of fittings and the extrapolational properties of the fitted parameters are discussed. Formulas in terms of basic molecular properties for some of the parameters of the effective dipole moment matrix elements are derived. Values of these parameters calculated from the theoretical formulas using the force field and dipole moment expansions of Wattson and Rothman (1992, J. Quant. Spectrosc. Radiat. Transfer 48, 763-780) have been compared with corresponding fitted values. Copyright 1998 Academic Press. Copyright 1998Academic Press

Infrared Fundamental and First Hot Bands of O12C17O Isotopic Variants of Carbon Dioxide.

Infrared spectra of 16O12C17O, 17O12C17O, and 17O12C18O in a carbon dioxide sample enriched with oxygen-17 have been recorded with a resolution of about 0.0025 cm-1 in the regions of the fundamental bands, nu2 (600-800 cm-1) and nu3 (2200-2400 cm-1), and in the region of the "forbidden" band, nu1 (1200-1400 cm-1), using the long path difference Fourier transform spectrometer of the LPMA in Paris. For each species, the first hot band in the 4.5-µm region and two hot bands at least in the 15-µm region have been studied for the first time, and a simultaneous reduction of wavenumbers measured in different spectral regions has been carried out yielding new or improved spectroscopic constants. Line intensities have been measured in the region of the nu2 and nu3 bands of 16O12C17O, and the corresponding rotationless transition dipole moments and Herman-Wallis coefficients have been reported. Copyright 1998 Academic Press.

Line Intensities of (12)C(16)O(2) in the 1.2-1.4 µm Spectral Region.

The 7000-8500 cm(-1) spectral region of (12)C(16)O(2) has been investigated using the high-resolution FT spectrometer of LPPM in Orsay. The two strongest bands in this region are the 10031 <-- 00001 and 10032 <-- 00001 bands centered at 8294 and 8192 cm(-1). Line intensities in these two bands and in the 40013 <-- 00001 and 40014 <-- 00001 bands have been measured. Using the method of effective operators, these line intensities have been included in a new fit of effective dipole-moment parameters to all available experimental data in the same spectral region of (12)C(16)O(2). The corresponding calculated line intensities of the 10031 <-- 00001 and 10032 <-- 00001 bands are compared with the experimental ones. Copyright 2000 Academic Press.

Dipole-Moment Derivatives of Nitrous Oxide.

The equations relating the q(2)J-type parameters of the matrix elements of the effective dipole-moment operator with the force field constants and the dipole-moment derivatives have been established by means of contact transformations in the case of nitrous oxide molecule. The effective dipole-moment operator corresponds to the reduced effective Hamiltonian derived by J.-L. Teffo, V. I. Perevalov, and O. M. Lyulin (J. Mol. Spectrosc. 168, 390-403 (1994)) for the global treatment of the vibrational-rotational energy levels of this molecule. Using these equations, the first and second derivatives of the dipole-moment function of the nitrous oxide molecule have been determined from the published values (O. M. Lyulin, V. I. Perevalov, and J.-L. Teffo, J. Mol. Spectrosc. 174, 566-580 (1995)) of the matrix element parameters of the effective dipole-moment operator. Copyright 2001 Academic Press.

Line Positions and Absolute Intensities in the Laser Bands of Carbon-12 Oxygen-17 Isotopic Species of Carbon Dioxide.

Infrared spectra of a carbon dioxide sample enriched with oxygen-17 have been recorded with a resolution of about 0.0025 cm-1 in the region of the laser bands near 10 and 9 µm, using the long path difference Fourier Transform Spectrometer of the LPMA in Paris. The two laser bands of the 16O12C17O and 17O12C18O species have been analyzed for the first time. Line intensities for several isotopic species have been measured in this region and the rotationless transition dipole moments and Herman-Wallis coefficients of the corresponding bands have been reported. In particular intensities, alternation in the spectra of 17O12C17O has been analyzed. Copyright 1999 Academic Press.

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

The (1 0(0) 5)1,2 --> (1 0(0) 4)1,2 and (1 0(0) 6)1,2 --> (1 0(0) 5)1,2 emission bands of 12C16O2 have been recorded near 4.5 µm by Fourier transform spectroscopy of a CO2 + N2 mixture excited by dc discharge. The spectroscopic parameters of the (1 0(0) v3)1,2 vibrational states with v3 = 0-6 have been obtained from a global rotational analysis of the six (1 0(0) v3)1,2 --> (1 0(0) (v3-1))1,2 emission bands (v3 = 1-6). The (1 0(0) 5)1,2 vibrational states of both 12C16O2 and 13C16O2 have been observed by direct absorption from the vibrational ground state by Intracavity Laser Absorption Spectroscopy near 12 700 and 12 400 cm-1, respectively. The rovibrational energy levels obtained by the two experimental techniques are discussed and compared with those calculated in the framework of the effective operator approach. Copyright 1999 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.