N.N. Lavrentieva

CDSD-1000, the high-temperature carbon dioxide spectroscopic databank

Abstract We present a high-temperature version, CDSD-1000, of the carbon dioxide spectroscopic databank. The databank contains the line parameters (positions, intensities, air- and self-broadened half-widths and coefficients of temperature dependence of air-broadened half-widths) of the four most abundant isotopic species of the carbon dioxide molecule. The reference temperature is T ref =1000 K and the intensity cutoff is I cut =10 −27 cm −1 / molecule cm −2 . More than 3 million lines covering the 260–8310, 418–2454, 394–4662, and 429– 2846 cm −1 spectral ranges for 12 C 16 O 2 , 13 C 16 O 2 , 12 C 16 O 18 O , and 12 C 16 O 17 O , respectively, are included in CDSD-1000. 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. Line-by-line simulations of several low- and medium-resolution high-temperature (T=800– 3000 K ) spectra have been performed in order to validate the databank. Comparisons of CDSD-1000 with other high-temperature databanks HITEMP, HITELOR, and EM2C are also given. CDSD-1000 is able to reproduce observed spectra in a more satisfactory way than the high-resolution databank HITEMP for temperatures higher than 1000 K . The databank is useful for studying high-temperature radiative properties of CO2. CDSD-1000 is freely accessible via the Internet.

Semi-empiric approach to the calculation of H2O and CO2 line broadening and shifting

Abstract A semi-empiric approach to the calculation of spectral line half-widths and shifts is proposed. This approach is based on the Anderson approximation and includes the correction factors, the parameters of which can be determined by fitting the broadening or shifting coefficients to the experimental data. This allows sufficiently accurate predictions of the parameters of line profiles that were not measured. The coefficients of CO2 and H2O spectral line broadening and shifting due to air and nitrogen pressure are calculated, as well as the coefficients of their temperature dependence. The calculated coefficients agree satisfactorily with measured values.

J-dependence of the lineshift coefficients in the ν2 water vapor band

Abstract The nitrogen pressure shifting coefficients for the 150 water vapor lines in the ν 2 band have been measured with the Fourier transform spectrometer located at the Paris VI University with the spectral resolution of 0.005 cm −1 and at room temperature. The measurements were performed for lines having lower state angular moment up to 16, the measured values are found to range from + 0.015 to −0.0293 cm −1 /atm. The J -dependence of the line shift coefficients was studied using the Anderson-Tsao-Curnutte model and cut-of-free method. Fairly satisfactory agreement between measured and calculated line shift coefficients has been found.

Self- and air-broadening coefficients of HD16O spectral lines

We present the line broadening and self-broadening coefficients of the water isotopologue HD16O and study their dependence on quantum numbers up to J = 50 for P-, Q-, and R-branches. Three calculation techniques have been used: the analytical model in the case of known quantum transition identification in normal modes; the JJ′ dependence in the case when only J and level symmetry are known, and the semiempirical calculation technique for 50 ≥ J > 15. The derived regularities for the broadening coefficients of water vapor lines allow accurate calculation of HD16O spectra including millions of weak lines from the VTT line list (Voronin, Tennyson, and Tolchenov).

Influence of isotopic substitution in the absorbing molecule on the self-broadening coefficients of carbon dioxide spectral lines

The dipole moment effect, which occurs due to isotopic substitution of one oxygen atom in the absorbing molecule, on the collisional half-width of rotational-vibrational lines in the ν3 band in the case of perturbation by the main isotopologue 16O12C16O is investigated. Self-broadening coefficients of lines of the carbon dioxide isotopologues are calculated by two methods: semi-empirical and semi-classical. Weak but noticeable variations in the line halfwidths for different isotopologues are revealed when using both methods.

The Average Energy Difference Method for Calculation of Line Broadening of Asymmetric Tops

A new method for estimation of broadening coefficients of vibrational-rotational lines of asymmetric tops is presented. The method allows finding line widths on the basis of a few empiric data without complicated calculations. Based on the analysis of experimental data, the dependence of the average energy difference on vibrational quantum numbers is found. The approach has been tested by the example of calculation of line broadening of asymmetric tops H2O and HDO. Calculated parameters of line profiles were compared with experimental data in different absorption bands.

Collisional broadening of CO2 lines by N2O pressure

Carbon dioxide line broadening coefficients by N2O pressure, as well as their temperature exponents, were calculated for a wide range of rotational quantum numbers in the 0001–1000 band. A semiempiric method that is based on the semiclassical broadening theory was used. It showed good results in calculations of half-widths and shifts of lines by pressure for H2O-N2(O2), CO2-N2(O2), and O3-N2(O2) systems. The calculated collisional half-widths were compared with the measured data obtained with a frequency-stabilized tunable CO2 laser for 11 vibrational-rotational transitions with rotational quantum numbers of the lower state to 38 at room temperature and for three transitions R(10), R(22), and R(32) in the temperature interval of 300 ≤ T ≤ 700 K in the 0001–1000 band. The calculated and measured data are in a good agreement.

Approximation of resonance functions for exact trajectories in the pressure-broadening theory. Real parts

An analytical formula for approximation of the real parts of resonance functions in the pressure-broadening theory is proposed. The trajectories are computed from the isotropic Lennard–Jones (6–12) potential using ordinary equations of classical mechanics. The proposed analytical formula is a part of a power series of hyperbolic tangents th(z). The coefficients of this series are determined for the real parts of nine resonance functions. A test calculation of broadening coefficients for HCl in argon is discussed.

Self-Broadening and Carbon-Dioxide Broadening of Lines of the H2S Molecule

Carbon-dioxide-broadening coefficients and self-broadening coefficients of lines of the main isotopic modification of Н2S are estimated on the basis of literature data. The J′-dependences of the above line-profile parameters of the hydrogen-sulfide molecule are examined. In the case of CO2 broadening, the half-widths of lines are calculated by a semiempirical method based on a parametric modification of the impact semiclassical model; the model parameters were determined from the fit to experimental data.

Calculation of line parameters of the ν 3 band of monodeuterated methane: Nitrogen broadening

Halfwidths and shifts of CH3D lines are calculated for the case of nitrogen broadening. The calculations are performed for room temperature (296 K) for vibrational–rotational lines in the ν3 parallel band, with the rotational quantum numbers varying in the ranges of 0 ≤ J ≤ 70 and 0 ≤ K ≤ 20. For each line, the temperature-dependence characteristics are calculated in the range of 200–400 K recommended for the HITRAN database. The calculations are carried out using a semiempirical method with a correction factor the parameters of which are adjusted on a number of experimental values.