Continuous measurements of stable isotopes of carbon dioxide and water vapour in an urban atmosphere: isotopic variations associated with meteorological conditions

Isotope ratios of carbon dioxide and water vapour in the near-surface air were continuously measured for one month in an urban area of the city of Nagoya in central Japan in September 2010 using laser spectroscopic techniques. During the passages of a typhoon and a stationary front in the observation period, remarkable changes in the isotope ratios of CO₂ and water vapour were observed. The isotope ratios of both CO₂ and water vapour decreased during the typhoon passage. The decreases can be attributed to the air coming from an industrial area and the rainout effects of the typhoon, respectively. During the passage of the stationary front, δ¹³C–CO₂ and δ¹⁸O–CO₂ increased, while δ²H–H₂Ov and δ¹⁸O–H₂Ov decreased. These changes can be attributed to the air coming from rural areas and the air surrounding the observational site changing from a subtropical air mass to a subpolar air mass during the passage of the stationary front. A clear relationship was observed between the isotopic CO₂ and water vapour and the meteorological phenomena. Therefore, isotopic information of CO₂ and H₂Ov could be used as a tracer of meteorological information.     

Frequency-stabilized cavity ring-down spectroscopy measurements of carbon dioxide isotopic ratios

Carbon dioxide (CO₂) isotopic ratios on samples of pure CO₂ were measured in the 1.6 μm wavelength region using the frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) technique. We present CO₂ absorption spectra with peak signal-to-noise ratios as high as 28,000:1. Measured single-spectrum signal-to-noise ratios were as high as 8900:1, 10,000:1, and 1700:1 for ¹³C/¹²C, ¹⁸O/¹⁶O, and ¹⁷O/¹⁶O, respectively. In addition, we demonstrate the importance of utilizing the Galatry line profile in the spectrum analysis. The use of the Voigt line profile, which neglects the observed collisional narrowing, leads to large systematic errors which are transition-dependent and vary with temperature and pressure. While the relatively low intensities of CO₂ transitions near λ=1.6 μm make this spectral region non-optimal, the sensitivity and stability of FS-CRDS enabled measurement precision of pure CO₂ samples which are comparable to those of other optical techniques which operate at far more propitious wavelengths. These results indicate that a FS-CRDS spectrometer designed to probe CO₂ bands near wavelengths of 2.0 μm or 4.3 μm could achieve significantly improved precision over the present instrument and likely be competitive with mass spectrometric methods.     

High sensitivity CW-cavity ring down spectroscopy of CO2 near 1.35 μm (II): New observations and line intensities modeling

In a previous contribution [Kassi S, Song KF, Campargue A. High sensitivity CW-cavity ring down spectroscopy of ¹²CO₂ near 1.35 μm (I): line positions. JQSRT 110 (2009) 1801-1814], the line positions analysis of the high sensitivity absorption spectrum of carbon dioxide has been reported in the 7123-7793 cm⁻¹ region. In this second contribution, the spectral region investigated by CW-cavity ring down spectroscopy has been extended up to 7917 cm⁻¹. It added about 400 lines to our previous list of about 2500 transitions. These additional lines include transitions belonging to six newly observed ¹²C¹⁶O₂ bands for which we provide the spectroscopic parameters. Over the whole 7123-7917 cm⁻¹ region, the accurate intensities of about 2900 lines belonging to four isotopologues (¹²C¹⁶O₂, ¹³C¹⁶O₂, ¹⁶O¹²C¹⁸O and ¹⁶O¹²C¹⁷O) were retrieved with an average accuracy of 3%. Intensity values range between 1.2×10⁻²⁹ and 4.1×10⁻²⁵ cm/mol. Compared to the present version of the carbon dioxide spectroscopic databank recently adopted for the HITRAN database, important deviations were evidenced for some weak bands of the main isotopologue. The CW-CRDS intensity data relative to a total of 46 ¹²C¹⁶O₂ bands together with selected intensity information available in the literature for nine bands have been fitted simultaneously using the effective operators approach. The ΔP=11 set of the ¹²C¹⁶O₂ effective dipole moment parameters has been refined leading to a much better agreement with the measured intensity values. In addition, the ΔP=10 effective dipole moment parameters of the ¹⁶O¹²C¹⁸O minor isotopologue were determined for the first time. The obtained results will help to improve the carbon dioxide spectroscopic databank (CDSD).     

Tunable diode laser measurement of pressure-induced shift coefficients of CO2 around 2.05 μm for Lidar application

Atmospheric carbon dioxide (CO₂) is one of the main contributors to the greenhouse effect. A global monitoring of CO₂ from space is foreseen as a key issue to quantify its sources and sinks at a regional scale and to better predict future levels of CO₂ and their effect on climate change. Differential Absorption Lidar (DiAL) is a promising and novel spectroscopic technique for remote sensing CO₂ spatial and temporal concentration distribution with a high level of accuracy. However, a precise knowledge of spectroscopic parameters of CO₂ molecular transitions and their dependence with temperature and pressure is required for reducing the uncertainty on DiAl measurements. Hence, to support remote sensing of carbon dioxide in the troposphere, we report on the accurate determination of air pressure-induced shift coefficients for eight absorption lines belonging to the R branch of (20⁰1)_III←(00⁰0)_I band of CO₂ at 2.05 μm. Purposely, a high-resolution tunable diode laser absorption spectrometer (TDLAS) coupled to a cryogenically cooled optical cell was implemented. From these measurements, we have further determined the temperature-dependencies of the air pressure-induced shift coefficients.     

Simultaneous thermogravimetry - mass spectrometry for a solid oxide fuel cell cathode: (La0.7Sr0.3)0.9MnO3

A SOFC cathode related perovskite material, (La_0.7Sr_0.3)_0.9MnO₃, has been investigated by simultaneous thermogravimetry - mass spectrometry from room temperature to 1770 K. Water, carbon dioxide and oxygen were detected by mass spectrometry. Water and carbon dioxide evolution can be interpreted by assuming that prior to the thermogravimetry-mass spectrometry measurement about 0.5 % of the lanthanum component had reacted with carbon dioxide and water to form La₂(CO₃)₃*8H₂O, which dehydrated and decomposed via La₂O₂CO₃ into La₂O₃ and evolving H₂O and CO₂ during the present experiment. The observation that the lanthanum strontium manganite emitted oxygen in two stages can be ascribed to the two different oxygen sites in the perovskite lattice, that is, the oxygen excess and deficient regions.     

Diode laser spectroscopy of H2O and CO2 in the 1.877-μm region for the in situ monitoring of the Martian atmosphere

A diode laser spectrometer was used in the laboratory to study H₂O and CO₂ line intensities and self-broadening coefficients around 1.877 μm. The spectral region ranging from 5327 cm^-1 to 5329 cm^-1, which is suitable for the in situ sensing of water vapor and carbon dioxide in the Martian atmosphere, was studied using a distributed feedback GaInSb diode laser from Nanoplus GmbH. We have studied one line from the (011)←(000)band of H₂O and two lines from the (01¹2)_I←(000) band of CO₂. The results of intensity and self-broadening measurements are compared to available databases, ab initio calculations and previous experimental determinations. Finally, we discuss the current development of the tunable diode laser absorption spectrometer instrument, a laser diode sensor devoted to the in situ measurement of H₂O and CO₂ in the Martian atmosphere. PACS 07.57.Ty; 07.87.+v     

Infrared degenerate four-wave mixing and resonance-enhanced stimulated Raman scattering in molecular gases and free jets

2 H₂), methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) in a cell under equilibrium conditions and cooled in free jet expansions. For methane at room temperature the detection limit was 2×10¹² molecules per cm³ and quantum state, enabling the detection of trace species with a spatial resolution of 1 mm²×30 mm. In an attempt to study transitions in the ν₁+ν₃ and 2ν₂+ν₃ combination bands of CO₂ or N₂O, it was not possible to observe any DFWM signal. Instead a surprisingly strong, backward- and forward-directed emission was found which could not be attributed to the DFWM process. The signal arising from this emission was more than 2 orders of magnitude stronger than the DFWM signals obtained for other molecules. The frequencies of the emitted radiation were found to correlate with the transitions ν₁+ν₃→ν₁ and 2ν₂+ν₃→2ν₂, respectively. Our investigations lead to the conclusion that the emission can be explained by stimulated Raman scattering, resonantly enhanced by transitions to the combination levels ν₁+ν₃ and 2ν₂+ν₃. This process seems to suppress the generation of DFWM signals. Received: 1 October 1996/Revised version: 6 January 1997     

Use of the optogalvanic effect (OGE) for isotope ratio spectrometry of 13CO2 and 14CO2

The use of isotopic carbon dioxide lasers for determination of carbon (and oxygen) isotope ratios was first demonstrated in 1994. Since then a commercial device called LARA^?, has been manufactured and used for Helicobacter pylori breath tests using ¹³C-labelled urea. The major advantages of the optogalvanic effect compared with other infrared absorption isotope ratio measurement techniques are its lack of optical background and its high sensitivity resulting from a signal gain proportional to laser power. Continuous normalisation using two cells, a standard and sample, lead to high accuracy as well as precision. Recent advances in continuous flow measurement of ¹³C/¹²C ratios of CO₂ in air and extensions of the technique to ¹⁴C, which can be analysed as a stable isotope, are described.     

Using a laser-based CO2 carbon isotope analyser to investigate gas transfer in geological media

CO₂ stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO₂ carbon isotope analysis provides continuous measurement at high temporal resolution and is a promising alternative to isotope ratio mass spectrometry (IRMS). We performed a thorough assessment of a commercially available CO₂ Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of δ ¹³C in CO₂. Using a set of reference gases of known CO₂ concentration and carbon isotopic composition, we evaluated the precision, long-term stability, temperature sensitivity and concentration dependence of the analyser. Despite good precision calculated from Allan variance (5.0 ppm for CO₂ concentration, and 0.05 ‰ for δ ¹³C at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of δ ¹³C on CO₂ concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO₂ concentration and 1.3 ‰ for δ ¹³C, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO₂ flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source.     

Comment on “Spectroscopic database of CO2 line parameters: 4300–7000 cm–1”

The “Spectroscopic database of CO₂ line parameters: 4300–7000 cm^–1” constructed by Toth et al., has been considered in relation with our previous and current studies of the absorption spectrum of carbon dioxide (CO₂) by high-sensitivity CW-cavity ring down spectroscopy (CW-CRDS) in the 5850–7000 cm^?1 region. Part of the line parameters of the database are based on accurate spectroscopic measurements by Fourier transform spectroscopy (FTS) but Toth et al. have chosen to fix to a very low value (4×10^?30 cm/molecule) the lower intensity cut off. This value which is far below the FTS detection limit has led to long range extrapolations to high J values and to the inclusion of weak unobserved bands which were theoretically predicted. In the 5850–7000 cm^?1 region, most of these calculated transitions were previously observed by CW-CRDS. The comparison with the CW-CRDS ¹³CO₂ spectrum in this region, has evidenced that (i) many weak bands above the intensity cut off are missing; (ii) there are important deviations between the line parameters provided in the database and our previous observations both for line positions (up to 1.7 cm^?1) and line intensities (up to a factor 80). Our discussion was limited to the three ¹³C species (¹³C¹⁶O₂, ¹⁶O¹³C¹⁸O and ¹⁶O¹³C¹⁷O) but the conclusions should apply to the other isotopologues in particular ¹²C¹⁶O₂ and to the full spectral range of the database.Alternatively, the global effective operators models for CO₂ can reproduce satisfactorily all the experimental line positions and line intensities available in the literature. This polyad model, which has been developed for most of the CO₂ isotopologues, constitutes an interesting alternative for the most accurate and complete CO₂ database. In particular, very weak bands, accidental resonances, intensity transfers and extra lines are accurately accounted for and predicted by this polyad model.     

Aerogel–copper nanocomposites prepared using the adsorption of a polyfluorinated complex from supercritical CO2

A supercritical deposition method has been used to synthesize aerogel?Ccopper nanocomposites. Carbon, resorcinol?Cformaldehyde, and silica aerogels (CAs, RFAs, and SAs) were impregnated with a new polyfluorinated copper precursor (CuDI6), which has a high solubility in supercritical carbon dioxide (scCO₂). Adsorption isotherms of CuDI6 onto various aerogels from scCO₂ were determined at 35?°C and 10.6?MPa using a batch method which is based on the measurement of the fluid phase concentration. The relative affinity between CuDI6 and different aerogels changed in the following order: CA?>?RFA?>?SA. The effect of temperature on the adsorption isotherms for the CuDI6?CCO₂?CCA system was also studied at 35 and 55?°C and at a CO₂ density of 736.1?kg/m³. The CuDI6 uptake at a particular CuDI6 concentration increased with increasing temperature. Adsorbed CuDI6 was found to convert into Cu and Cu/Cu₂O nanoparticles on the aerogel supports after chemical or thermal treatments at ambient pressure and at temperatures ranging from 200 to 400?°C.     

Quantum chemical studies on a series of transition metal carbon dioxide complexes: Metal–carbon bonding and electronic structures

The bonding features and electronic structures of a series of transition metal carbon dioxide complexes have been studied by density functional theory (DFT) calculations combined with natural bond orbital (NBO) analysis and energy-decomposition analysis (EDA). NBO analysis shows that the interaction between the metal center and the carbon atom of the carbon dioxide ligand (M–C) is stronger than the other interaction between the metal center and the carbon dioxide ligand. Natural hybrid orbital (NHO) analysis gives the detailed bonding features of the M–C bond for each complex. The NBO charge distribution on the carbon dioxide unit in all studied complexes is negative, which indicates charge transfer from the metal center to the carbon dioxide ligand for all studied complexes. The hyperconjugation effect of the metal center and the two C–O bonds of the carbon dioxide ligand has been estimated using the NBO second-order perturbation stabilization energy. It was found that the NBO second-order stabilization energy of C–O?→?nM* is sensitive to the coordinated sphere and the metal center. Frontier molecular orbital (FMO) analysis shows that complexes 1 and 4 may be good nucleophilic reagents for activation of the carbon dioxide molecule. However, the EDAs show that the M–CO₂ bond interaction energy of complex 4 is about two times as large as that of complex 1. The high M–CO₂ bond interaction energy of complex 4 may limit its practical application.     

Far-infrared laser emission from deuterated ammonia

By optically pumping the deuterated isotopomers of ¹⁴NH₃ and ¹⁵NH₃ using ¹²C¹⁶O₂, ¹³C¹⁶O₂, ¹²C¹⁸O₂, and ¹³C¹⁸O₂ lasers, several new far-infrared (FIR) emission lines between 65 μm and 125 μm have been detected. The existing spectroscopy of ¹⁴N-ammonia isotopomers has been used to identify many of these lines, as well as some previously observed but unidentified. The spectroscopic data have been analyzed to predict over 20 additional FIR laser lines that could be pumped by a more capable CO₂ laser. This effort was motivated by a need for strong laser lines in frequency coincidence with molecular transitions of astrophysical interest. Of particularnote is the measurement of the 2680-GHz line of ¹⁴NHD₂, whose frequency is 4.9 GHz higher than that of the important J=1-0 line of interstellar HD. Received: 25 July 2002 / Published online: 20 December 2002 RID="*" ID="*"Corresponding author. Fax: +1-303/492-5941, E-mail: boreiko@spot.colorado.edu     

Spectroscopic requirements for ACCURATE, a microwave and infrared-laser occultation satellite mission

The proposed satellite mission ACCURATE consists of a small constellation of satellites in low Earth orbit, combining microwave occultation for thermodynamic state profiling with infrared-laser occultation for greenhouse gas and line-of-sight wind profiling. The mission aims to detect six greenhouse gas molecules with four additional isotopologues (H₂O, CO₂, CH₄, N₂O, O₃, CO, ¹³CO₂, OC¹⁸O, HDO, and H₂¹⁸O) in the upper troposphere and lower stratosphere in the 4000-5000 cm⁻¹ spectral region. Greenhouse gas profiles will be retrieved to within 1-2% accuracy using a ‘differential’ method, requiring two spectral points for each species - one to sample the spectral line and the other nearby to sample the baseline.An estimation of retrieval errors for the ACCURATE mission reveals that errors in spectroscopic line parameters dominate all other error sources. Poor knowledge of the spectroscopy introduces systematic errors into the retrieved greenhouse gas profiles. Using a simple approach, it was shown that the best line parameters currently available are too large to allow retrievals of greenhouse gases to within the stated ACCURATE mission goals of 1% accuracy for CO₂ and 2% for all other species. Therefore, spectroscopic line parameters for targeted lines need to be improved before the ACCURATE mission can be launched. Requirements have been formulated in this direction, and laboratory experiments outlined that could meet these requirements.     

Study of gas detection based on integrated cavity output spectroscopy

A trace gases detection system based on integrated cavity output spectroscopy (ICOS) was developed, where a NIR tunable diode laser (TDL) was used as light source, an optical cavity composed by two plan-concave mirrors with reflection near 99.7% was used as the absorption cell. Trace water vapour (H₂O), carbon dioxide (CO₂), methane (CH₄), carbon monoxide (CO) and mixture of CO₂ and CO were tested by ICOS based on the characteristics absorption. The wavelength calibration, cavity transmission characteristics, quantitative measurement ability and sensitivity of the TDL-ICOS were also studied, and a evaluated minimum detectable sensitivity of 1.15 × 10^?7 cm^?1 was obtained when the system was used to CH₄ detection. The experiment results show that TDL-ICOS is expected to be a reliable and promising system for the detection of trace gases since it has some advantages such as real-time monitoring, simple device, easy operation, high sensitivity, good stability and quantitative ability.     

High sensitivity CW-Cavity Ring Down Spectroscopy of five CO2 isotopologues of carbon dioxide in the 1.26-1.44 μm region (I): Line positions

The absorption spectrum of highly enriched ¹³C carbon dioxide has been investigated by CW-Cavity Ring Down Spectroscopy with a setup based on fibered distributed feedback (DFB) laser diodes. By using a series of 30 DFB lasers, the CO₂ spectrum was recorded in the 7029-7917 cm⁻¹ region with a typical sensitivity of 3×10⁻¹⁰ cm⁻¹. The uncertainty on the determined line positions is on the order of 8×10⁻⁴ cm⁻¹. More than 3800 transitions with intensities as low as 1×10⁻²⁹ cm/molecule were detected and assigned to the ¹³C¹⁶O₂, ¹⁶O¹³C¹⁷O, ¹⁶O¹³C¹⁸O, ¹⁷O¹³C¹⁸O and ¹³C¹⁸O₂ isotopologues. For comparison, only 104 line positions of ¹³C¹⁶O₂ were previously reported in the literature in the considered region. The band-by-band analysis has led to the determination of the rovibrational parameters of a total of 83 bands including 56 bands of the ¹³C¹⁶O₂ species. The measured line positions of ¹³C¹⁶O₂ and ¹⁶O¹³C¹⁸O were found in good agreement with the predictions of the respective effective Hamiltonian (EH) models but the agreement degrades for the minor isotopologues. Several cases of resonance interactions were found and discussed. In the 20033-10002 band of ¹³C¹⁶O₂, an anharmonic resonance interaction leads to deviations on the order of 0.05 cm⁻¹ compared to the EH predictions. The existence of interpolyad interactions affecting the non-symmetric isotopologues of carbon dioxide is confirmed by the observation of two occurrences in ¹⁶O¹³C¹⁷O and ¹⁶O¹³C¹⁸O. The obtained results improve significantly the knowledge of the spectroscopy of the ¹³C isotopologues of carbon dioxide. They will be valuable to refine the sets of effective Hamiltonian parameters used to generate the CDSD database.     

An XPS and UPS study of the kinetics of carbon monoxide oxidation over Ag(111)

The oxidation of carbon monoxide over a Ag(111) catalyst has been studied by XPS and UPS. The kinetics have been determined over the temperature range of 180 to 400 K and found to be of the Langmuir-Hinshelwood type, although the Eley-Rideal mechanism is mimicked. A negative activation energy, ?1.7 kcal/mole, and a preexponential, 6 × 10^?18 cm², are found. The former corresponds to the difference in the activation energies for carbon monoxide desorption and for carbon monoxide oxidation (leading to CO₂ desorption). At 90 K, upon carbon monoxide exposure to the active oxygen precovered surface, the O ls and C ls spectral regions show the formation of CO₂-like and carbonate species; the latter is stable to at least room temperature. That is, at 90 K, the residence time and mobility of CO₂ formed at the surface permits a new surface reaction — the formation of stable surface carbonate. The identifications are based on C and O coverages and on line positions from the literature for Cu/CO₂ and several bulk carbonates. With UPS, the 1π_g, the unresolved doublet 1π_u and 3σ_g, and the 4σ_g molecular orbitals of adsorbed CO₂-like species are identified, as well as the unresolved triplet 1α′₂, 1e″ and 4e′ and the unresolved triplet 3e′, 1α″₂ and 4a′ molecular orbitals of the carbonate species. Surface CO₂-like species formed by surface oxidation of CO seem to be more strongly bound than reversibly adsorbed CO₂.     

New method for isotopic ratio measurements of atmospheric carbon dioxide using a 4.3 μm pulsed quantum cascade laser

We present a new approach to the measurement of stable isotopic ratios of carbon dioxide using a near-room-temperature pulsed quantum cascade laser and a spectral ratio method based upon dual multiple pass absorption cells. The spectral ratio method improves precision and accuracy by reducing sensitivity to variations in the laser tuning rate, power and line width. The laser is scanned across three spectral lines (near 2310 cm^-1) quantifying three CO₂ isotopologues: ¹²C¹⁶O₂, ¹³C¹⁶O₂ and ¹²C¹⁶O¹⁸O. Isotopic ratios are determined simultaneously with a precision of 0.2δ for each ratio with a one-second measurement. Signal averaging for 400 s improves the precision to better than 0.03δ for both isotopic ratios (¹³ R and ¹⁸ R). Long-term accuracy of 0.2 to 0.3δ is demonstrated with replicate measurements of the same sample over a one-month period. The fast time response of this instrument is suitable for eddy flux measurements. PACS 07.57.Ty; 42.62.Fi; 92.70.Cp; 91.67.Rx     

13CO2/12CO2 isotopic ratio measurements using a difference frequency-based sensor operating at 4.35 micrometers

A portable modular gas sensor for measuring the ¹³C/¹²C isotopic ratio in CO₂ with a precision of 0.8‰(±1σ) was developed for volcanic gas emission studies. This sensor employed a difference frequency generation (DFG)-based spectroscopic source operating at 4.35 μm (∼2300 cm^-1) in combination with a dual-chamber gas absorption cell. Direct absorption spectroscopy using this specially designed cell permitted rapid comparisons of isotopic ratios of a gas sample and a reference standard for appropriately selected CO₂ absorption lines. Special attention was given to minimizing undesirable precision degrading effects, in particular temperature and pressure fluctuations. Received: 16 April 2002 / Revised version: 28 May 2002 / Published online: 21 August 2002 RID="*" ID="*"Corresponding author. Fax: +1-713/5245237, E-mail: fkt@rice.edu     

High sensitivity CW-CRDS spectroscopy of CO2, OCO and OCO between 5851 and 7045 cm: Line positions analysis and critical review of the current databases

The exhaustive line positions analysis of the absorption spectrum of carbon dioxide in natural abundance has been performed on the basis of high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 7045 cm⁻¹ (1.71-1.42 μm). The achieved sensitivity (noise equivalent absorption α_min ∼ 2-5 × 10⁻¹⁰ cm⁻¹) have allowed the detection of 8293 transitions of the ¹²C¹⁶O₂, ¹⁶O¹²C¹⁷O and ¹⁶O¹²C¹⁸O isotopologues. They belong to a total of 130 bands. Line intensities of the weakest transitions are on the order of 2 × 10⁻²⁹ cm/molecule. The rovibrational assignments were performed on the basis of accurate predictions of the effective Hamiltonian model of the respective isotopologues. The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 121 bands from a fit of the measured line positions. A number of resonance interactions were identified. In particular, the first observation of an interpolyad coupling is reported for the ¹⁶O¹²C¹⁸O isotopologue. The results of the complete line positions analysis are provided as Supplementary material.The obtained experimental dataset which is the most complete in the considered region, has been used for a critical review of the most currently used spectroscopic databases of carbon dioxide: HITRAN, GEISA, HITEMP, and the recent JPL and CDSD databases.