Comparison and assessment of procedures for calculating the R(12) line strength of the ν1+ 2 ν2 + ν3 band of CO2

Abstract

Recently, results for the CO(2) R(12) line strength parameter have been reported, which differ significantly and are inconsistent with respect to quoted uncertainties. We investigate to what extent this inconsistency might be caused by the chosen data analysis methods. To this end, we assess and compare a parametric fitting procedure and a non-parametric approach. We apply the methods to simulated and measured line spectra, and we specify the conditions required for the safe application of the two procedures. For our present data, the corresponding conditions are satisfied for both methods, and consistent results are obtained. However, the simulations reveal that the fitting procedure can show shortcomings when the uncertainty in the wavenumber is large.

Laser-spectrometric gas analysis: CO2–TDLAS at 2 µm

“…It should be noted here, that the unresolved discrepancy between R(12) line strength figures from [59] and [60] is intended to be the object of a new upcoming joint investigation of both author groups [61]. For the time being, the discrepancy's status is described by the fact that the value from [59] is very close to the updated value reported in the HITRAN 2008 edition [39], whereas the value from [60] has been reconfirmed recently [62], such that it does not bridge the difference in the two figures.…”

“…where n is the refractive index of silicon [62] and d is the length of the etalon. d = z + a + q + r, with z being the reading of a calliper, a is the correction due to the Abbe error of the calliper, q is the correction due to parallel reading and r is the correction due to the resolution of the calliper.…”

Advances in reference materials and measurement techniques for greenhouse gas atmospheric observations

“…However, when using line profiles with at least one more degree of freedom than the Voigt, relative differences between fitted areas are nominally 0.05% and difficult to distinguish. In the last decade line intensity measurements with relative uncertainties typically near 1% and approaching 0.1% have been reported [160,165,169,170]. Accurate measurements have also been reported using other techniques including traditional FTIR (see section 4.4), and direct TDLAS (see section 4.3) and cavity-enhanced laser spectroscopy methods.…”

Line strength measurements and relative isotopic ratio 13C/12C measurements in carbon dioxide using cavity ring down spectroscopy

“…In the recent years many laboratory studies were carried out to determine CO 2 absorption spectra in various spectral regions. Measurements with carbon dioxide including different isotopologues were performed, using various spectroscopic methods such as Fourier Transform Spectroscopy, Cavity Ring Down Spectroscopy (CRDS) and other laser-based spectroscopic methods [6][7][8][9][10][11][12][13][14] . In the * Corresponding author.…”