Absolute line intensities of CO2 in the 3090-3920 cm region

Absolute line intensities of ¹³C¹⁶O₂ were retrieved from high-resolution Fourier transform spectra recorded in the region 3090-3920 cm⁻¹. The uncertainty of the line intensity determination is estimated to be between 3 and 5% for the strong lines. The global fittings of the observed line intensities within the framework of the effective operators approach have been performed, reaching the experimental accuracy. A comparison of newly measured line intensities with those found in the HITRAN database is presented.     

Absorption spectra of CO2 and CO2 near 1.05 μm

The absolute line intensities of the Fermi triad 2003i-00001 (i = 1, 2, 3) of ¹²C¹⁶O₂ and ¹³C¹⁶O₂ isotopic species of carbon dioxide were retrieved from Fourier-transform spectra recorded at Doppler limited resolution in the region 9200-9700 cm⁻¹. The accuracy of the line intensity determination is estimated to be better than 15% for most lines. The vibrational transition dipole moments squared and Herman-Wallis coefficients have been determined. The global fittings of the observed line intensities within the framework of the effective operators method have been performed. The fitting results reproduce the data within experimental uncertainty.     

CO2: Global Treatment of Vibrational–Rotational Spectra and First Observation of the 2ν1 + 5ν3 and ν1 + 2ν2 + 5ν3 Absorption Bands

The effective operator approach is applied to the calculation of both line positions and line intensities of the ¹³C¹⁶O₂ molecule. About 11 000 observed line positions of ¹³C¹⁶O₂ 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 ν₂ and 3ν₂ 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 2ν₁ + 5ν₃ and ν₁ + 2ν₂ + 5ν₃ 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.     

Infrared Spectra of the OCO and OCO Species of Carbon Dioxide: The Region 500-1500 cm

The effective operator approach is applied to the calculation of the spectra of ¹⁶O¹²C¹⁷O and ¹⁶O¹²C¹⁸O in the far infrared. Using the eigenfunctions of the effective Hamiltonians previously derived for each of these species, parameters of the corresponding effective dipole moment operators have been fitted to more than 400 observed line intensities of cold and hot bands covering the ν₂ and ν₁ spectral regions. New line intensities measurements in the ν₂ band region of ¹⁶O¹²C¹⁸O have been performed. The new observed line intensities have been also included into the corresponding fit. The fittings have been achieved within the experimental errors. A comparison of calculated line parameters with those provided by the HITRAN and GEISA databases is given.     

High sensitivity cavity ring down spectroscopy of 13C16O2 overtone bands near 806 nm

The absorption spectrum of ¹³C¹⁶O₂ near 806 nm has been recorded with a continuous-wave cavity ring-down spectrometer. Two cold bands and one associated hot band are observed in this region. The line positions of these bands are determined with an accuracy of 0.003 cm^?1. The absolute line intensities have also been retrieved with an estimated accuracy of 4% for majority of the unblended lines. The vibrational transition dipole moment squared values and the empirical Herman–Wallis coefficients are determined for all the three bands. The comparison of the retrieved line positions and intensities to those given in the Carbon Dioxide Spectroscopic Databank shows large deviations in the line intensities of the 10052–00001 band. The effective dipole moment parameters describing the line intensities of ¹³C¹⁶O₂ near 806 nm are fitted according to the observed line intensities.     

Line Intensities in the ν6 Fundamental Band of CH3Br at 10 μm

Fourier transform spectra have been obtained at 296 K at a resolution of 0.002 or 0.004 cm^-1 depending on the pressure range. Line positions and intensities of CH₃⁷⁹Br and CH₃⁸¹Br belonging to the fundamental band ν₆ were measured and analyzed between 890 and 1080 cm^-1. A total of 2896 (2838) line positions with J≤60 and K≤6 was fitted with a root-mean-square deviation of 0.00028 (0.00021) cm^-1 for CH₃⁷⁹Br and CH₃⁸¹Br, respectively, within the experimental accuracy. The fit to 316 (312) measured intensities yielded values of the dipole moment derivatives of both isotopes with a standard deviation of 5% to be compared to an experimental uncertainty equal to 6% or better. A prediction of the line positions and intensities has been generated for atmospheric purposes with all lines from 820 to 1120 cm^-1 with intensities greater than 10^-5 cm^-2 atm^-1.     

Line positions and intensities of acetylene in the 2.2-μm region

More than 440 line positions and intensities of 8 bands of acetylene are measured in the 2.2-μm spectral region. A multispectrum fitting procedure has been applied to retrieve line parameters. The average absolute accuracy of the line parameters obtained in this work is estimated to be ±0.0005 cm⁻¹ for the line positions, and ±5% for the line intensities. Vibrational transition dipole moment and Herman-Wallis coefficients are determined for two of the studied bands. An unusual rotational dependence of the vibrational-rotational transition dipole moment of remaining bands has been found. All measured line intensities are treated simultaneously within the framework of the effective operators approach. The sets of effective dipole moment parameters obtained reproduce the observed line intensities within the experimental uncertainty.     

Line intensities in the 1.5-μm spectral region of acetylene

Line intensities are measured for 546 transitions belonging to 13 bands of the main isotopologue ¹²C₂H₂ of the acetylene molecule, in the 1.5-μm spectral domain. A multispectrum fitting procedure is used to retrieve line parameters from Fourier transform spectra. Prior to this work, line intensities were known for only 4 bands in this spectral region, from the work of El Hachtouki and Vander Auwera [Absolute line intensities in acetylene: the 1.5 μm region. J Mol Spectrosc 2002;216:355-62]. An excellent agreement is found with the results of these authors, showing that the accuracy of both results is likely better than 1% for the strong bands. However, the spectrum becomes very crowded when one wants to study weaker bands, so that the average accuracy of the intensities reported in the present work is 5%. From these data, vibrational transition dipole moments squared and Herman-Wallis coefficients have been determined for all the bands.     

CDSD-4000: High-resolution, high-temperature carbon dioxide spectroscopic databank

We present a high-resolution, high-temperature version of the Carbon Dioxide Spectroscopic Databank called CDSD-4000. The databank contains the line parameters (positions, intensities, air- and self-broadened half-widths, coefficients of temperature dependence of air- and self-broadened half-widths, and air-broadened pressure shifts) of the four most abundant isotopologues of CO₂. A reference temperature is 296 K and an intensity cutoff is 10⁻²⁷ cm⁻¹/molecule cm⁻² at 4000 K. The databank has 628,324,454 entries, covers the 226-8310 cm⁻¹ spectral range and designed for the temperature range 2500-5000 K. Format of CDSD-4000 is similar to that of HITRAN-2008. The databank has been generated within the framework of the method of effective operators and based on the global fittings of spectroscopic parameters (parameters of the effective Hamiltonians and effective dipole moment operators) to observed data collected from the literature. The databank is useful for studying high-temperature radiative properties of CO₂, including exoplanets atmospheres, aerothemal modeling for Mars entry missions, high-temperature laboratory spectra, and industrial applications. CDSD-4000 is freely accessible via the Internet site ftp://ftp.iao.ru/pub/CDSD-4000.