Analysis of Fourier transform spectra of N₂O in the ν₃ band for atmospheric composition retrievals

Abstract

We report measurement results for line positions, intensities, half-width, and pressure-induced shift coefficients and line mixing coefficients for N2O broadened by air in the ν3 band. The high signal-to-noise ratio spectra have been recorded at high resolution using the McMath–Pierce Fourier transform spectrometer formerly located at the National Solar Observatory on Kitt Peak, Ariz., USA. The spectra were analyzed using a multispectrum nonlinear least-squares curve-fitting technique employing the speed-dependent Voigt profile with a Rosenkranz (weak) line mixing component. The speed dependence parameters were calculated as suggested in the study of Kochanov (J. Quant. Spectrosc. Radiat. Transf. 189, 18 (2017). doi: 10.1016/j.jqsrt.2016.11.007 ). Several comparisons have been performed between the retrieved parameters and previously published results. For |m| ≤ 40, our results for line positions, broadening, and line mixing coefficients agree best with the results of Loos et al. (J. Quant. Spectrosc. Radiat. Transf. 151, 300 (2015). doi: 10.1016/j.jqsrt.2014.10.008 ). Also, we compared the obtained line positions and intensities with the corresponding values in HITRAN2016 and GEISA-2015 databases. No significant or systematic differences were noticed. The precision of our line positions was estimated to be 3 × 10−5 cm−1. The reported line positions, intensities, and air-broadening coefficients are accurate to better than 2%. The accuracy of air-pressure-induced line shifts and line mixing coefficients is better than 5%. The line mixing coefficients and air-broadening coefficients were also calculated using the exponential power gap scaling law, and these calculated values were found to be in good agreement with the experimental results.

Air-broadened N2O line-shape parameters and their temperature dependences by requantized classical molecular dynamics simulations

“…Note that the latter were retained in the last version of the HITRAN database [36]. The results of [15] are plotted in Fig. 3, showing a very good agreement with an average difference of about 1%…”

“…between our sdV values and those of [15]. Our Voigt values are compared with those of [37][38][39] (Fig.…”

“…In [14], line-mixing and speed-dependence effects were taken into account in the analysis of air-broadened N2O spectra in the 3 band, measured at room temperature with a Fourier Transform Spectrometer. This band was then measured and analyzed in [15] with the same line-shape model, the obtained line parameters being in good agreement with those of [14]. In [16] spectroscopic parameters for twenty N2broadened N2O lines in the 33 band were retrieved from spectra measured with a comb-assisted cavity ring-down spectrometer using the speed-dependent Voigt profile.…”

“…Comparisons between the coefficients obtained with the three profiles show that the values obtained with the V profile are, on average, 4% smaller than those obtained with the sdV and sdNG models. To the best of our knowledge, the speed-dependence of the line width for air-broadened 9 N2O lines was investigated in [14] and [15] only, both for the 𝜈 band. Since our rCMDS are corrected using the experimental values of [14], our rCMDS-deduced values for 𝛾 using the sdV profile are almost identical to those of [14] (see Table 1 of the present paper and Table 3 of [14]).…”

“…Room temperature values of the speed dependence coefficients, 𝛾 , retrieved from the corrected-rCMDS spectra using the sdV and sdNG profiles are listed in Table 1 and plotted in Fig. 5 (the corresponding ratio 𝛾 /𝛾 being plotted in the lower panel) where they are compared with those of [14] and [15]. In [14], a value of 𝛾 for each line was retrieved while in [15] a constant value of 0.0895 for 𝛾 /𝛾 was used for all the lines.…”