Jean-Yves Mandin

New improvements in the determination of line parameters from FTS data

Abstract The goal of the present work is to develop a method allowing us to obtain from Fourier-transform spectra the accurate line parameters needed by HITRAN and the companion high-temperature atlas HITEMP. The effects of the through-put and of the phase error on Fourier-transform spectra are discussed, and a method including these effects is described. This method has been applied to the determination of collisional widths of H2O in flame spectra.

Measurements of collisional linewidths in the ν 2 band of H 2 O from Fourier-transformed flame spectra

The collisional widths of more than 200 transitions belonging to the v(2) band of the H(2)O molecule were measured by using the Fourier-transformed spectra of an air-methane flame at 2000 K. A nonlinear least-squares method was used to determine the line widths for a wide range of J (up to 28) and K(a) (up to 14) quantum number values. Finally, an analysis of the results as functions of J and K(a) is presented.

Phase errors on interferograms: influence on the determination of positions, intensities, and widths of lines in the infrared

The effect of a phase error on line parameter measurements by using Fourier-transform spectra is studied, showing that, to obtain accurate results without modifying the interferogram, it is necessary to adjust a computed spectrum to an experimental spectrum in which the phase error is taken into account.

Broadening parameters of NO2 lines in the 3.4 μm spectral region

Abstract Fourier transform spectra have been recorded to measure self-, N 2 -, and O 2 -broadening coefficients of NO 2 lines in the v 1 + v 3 band. For the studied set of transitions, a slight rotational dependence of the broadening coefficients exists versus N ″, the rotational quantum number of the lower level of the transition, whereas no significant dependence is observed versus K a ″. An empirical relation, allowing one to calculate approximate values of the air-broadening coefficients γ air 0 , at 296 K, for lines observable in atmospheric spectra recorded from the ground, is proposed: γ air 0 = 84.1 − 0.753 N ″ + 0.0059 N ″ 2 , in 10 −3 cm −1 ·atm −1 , with an uncertainty of about ± 10% when N ″ and K a ″ are smaller than about 40 and 10, respectively. For typical lines used for atmospheric applications, the single value reported in the HITRAN database for all lines of all bands of NO 2 can differ by more than 20% from the measured ones.

Measurements of N2-induced shifts and broadening coefficients of lines in CO fundamental from Fourier transform spectra

Abstract N2-induced shifts and broadening coefficients of some lines in the fundamental band of CO have been derived from Fourier transform spectra using a non-linear least-squares procedure for fitting the experimental line shapes. Channeling fringes have been avoided by using wedged beam-splitter and mixer plates, and the remaining wavenumber-dependent phase error has been taken into account in the fitting procedure in order to derive accurate line positions. This method is discussed in detail along with the uncertainties in the obtained line shifts.

Rotational and vibrational dependences of collisional linewidths in the nν 2 –(n − 1)ν 2 hot bands of H 2 O from Fourier-transform flame spectra

The collisional widths of ~ 160 transitions belonging mainly to the 2nu(2)-nu(2), 3nu(2)-2nu(2), and 4nu(2)-3nu(2) hot bands of the H(2)(16)O molecule have been measured on Fourier-transform air-methane flame spectra at 2000 K and analyzed, showing a strong decrease in the collisional widths when the rotational quantum number J increases, as well as a nonnegligible decrease of the collisional widths when the nu(2) vibrational quantum number increases.

Absolute line intensities, vibrational transition moment, and self-broadening coefficients for the 3-0 band of 12 C 16 0

Accurate line parameters are missing in the near-infrared region, from 5000 to 10 000 cm−1 [1]. The 3-0 band of CO, an important molecule for standard purposes, is located in this spectral area, around 6350 cm−1.

Variation of the experimental conditions during the recording in FTS: Effects on the determination of line intensities and collisional widths

Abstract The errors which affect measured line intensities and collisional widths, because of the variation of the experimental conditions during the recording in FTS laboratory experiments, are studied. For step-by-step as well as for rapid scan interferometers, quasi-Doppler, Voigt, and quasi-Lorentzian line profiles are considered. As examples, the cases of adsorption and desorption, of decomposition of the absorbing gas, and of weak variation of the temperature, are discussed in detail.

Reanalysis of water-vapor high-resolution spectrum in 13200- to 16500-cm-1 region

The new analysis of water vapor high resolution spectra in 13200 - 16500 cm -1 region has been done using conventional scheme of the effective Hamiltonians in the Pade-Borel approximants representation. About 30 percent of new energy levels has been derived after the spectrum identification including the highest ever observed (0 10 0) [7 0 7] level. An alternative method of the spectrum identification using recent ab initio and variational calculations is discussed.