Line shape study of the carbon dioxide laser band Ι

Abstract

The spectral line parameters of carbon dioxide have been measured in the laser band I (00011 ← 10001) centred at 10.4 μm. The spectra were recorded at room temperature using the spectroscopic instrumentation at the far-infrared beamline, Canadian Light Source, Saskatoon, Sask. The spectral line intensities, air- and self- broadened Lorentz half widths, and pressure-induced shift coefficients were retrieved for 48 spectral lines using a multispectrum fit technique (Benner et al. J. Quant. Spectrosc. Radiat. Transfer, 53, 705 (1995)). Line parameters were retrieved using the Voigt and speed-dependent Voigt models. The deviations between our results and other results reported in the literature and in the HITRAN08 (Rothman et al. J. Quant. Spectrosc. Radiat. Transfer, 110, 533 (2009)) database were examined and discussed. The effect of errors in fitting channel spectra parameters was examined and found to be mitigated by the inclusion of channels in the multispectral fit.

A room temperature CO2 line list with ab initio computed intensities

“…In the laboratory it is much harder to determine accurately line intensities than line frequencies. Typical accuracies for experimental line intensity data used in atmospheric models and retrievals is only 3 to 10 % [9, 10,11,12] and, until recently, the best published measurements, e.g. Boudjaadar et al., [13], only provide accuracies in the 1 to 3 % range, still very significantly worse than the precision of 0.3 to 1 % required by the modern remote sensing experiments [14,15,16].…”

“…Line profiles are more difficult but significant progress on these has been made in recent years with, for example, the inclusion of line mixing in both the HITRAN database [7] and many retrieval models, and the move beyond Voigt profiles [8]. Here we focus on line intensities for the main isotopologue of carbon dioxide, 12 C 16 O 2 .…”

“…Recently there have been a number of laboratory measurements aimed at measuring absolute CO 2 line intensities with the high accuracy needed for remote sensing [17,18,19,12,20,21,22]. With the exception of recent work by Devi et al [21], these studies have all focussed on obtaining the highest possible accuracy for a few lines or even a single line.…”

The update of the line positions and intensities in the line list of carbon dioxide for the HITRAN2020 spectroscopic database

“…A systematic extrapolation method was introduced for producing the air-and self-half width (broadening) Voigt profile parameters for unmeasured transitions [61], based on the measurements reported in Ref. [62] The temperature-dependent exponents of the air-and selfbroadening parameters were generated based on existing measurements and a semi-empirical calculation method using the measurements given in Refs [63,64]. Air-and self-pressure shifts for every line of CO2 were calculated using the semi-empirical approach proposed by Hartmann [65] and fits using carefully selected experimental data.…”