V. Dana

The HITRAN molecular spectroscopic database and HAWKS (HITRAN atmospheric workstation)

Nineteen ninety-eight marks the 25th anniversary of the release of the first HITRAN database. HITRAN is recognized as the international standard of the fundamental spectroscopic parameters for diverse atmospheric and laboratory transmission and radiance calculations. There have been periodic editions of HITRAN over the past decades as the database has been expanded and improved with respect to the molecular species and spectral range covered, the number of parameters included, and the accuracy of this information. The 1996 edition not only includes the customary line-by-line transition parameters familiar to HITRAN users, but also cross-section data, aerosol indices of refraction, software to filter and manipulate the data, and documentation. This paper describes the data and features that have been added or replaced since the previous edition of HITRAN. We also cite instances of critical data that is forthcoming. A new release is planned for 1998.

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.

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.

12C16O2 line intensities in the 4.8 μm spectral region

Abstract In the 4.8 μm spectral region, intensities of lines belonging to the 3 following perpendicular bands of 12 C 16 O 2 have been measured: the ∏←∑ cold band 11101-00001 centered at 2076.856 cm -1 , the Δ←∏ hot band 12201-01101 centered at 2093.345 cm -1 , and the ∑←∏ hot band 20001-01101 centered at 2129.756 cm -1 . Fourier transform spectra, under a resolution limit of about 0.0023 cm -1 , have been used. For each band, the square of the vibrational dipole-moment matrix element and the Herman-Wallis coefficients have been determined. These results are compared with the previous experimental results included in the last edition of the HITRAN molecular database, as well as with new results obtained by the Direct Numerical Diagonalization method.

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.