CO Band Research Articles

Cavity ring-down spectroscopy of CO2 near λ = 2.06 µm: Accurate transition intensities for the Orbiting Carbon Observatory-2 (OCO-2) “strong band”

The λ = 2.06 µm absorption band of CO2 is widely used for the remote sensing of atmospheric carbon dioxide, making it relevant to many important top-down measurements of carbon flux. The forward models used in the retrieval algorithms employed in these measurements require increasingly accurate line intensity and line shape data from which absorption cross-sections can be computed. To overcome accuracy limitations of existing line lists, we used frequency-stabilized cavity ring-down spectroscopy to measure 39 transitions in the 12C16O2 absorption band. The line intensities were measured with an estimated relative combined standard uncertainty of ur = 0.08 %. We predicted the J-dependence of the measured intensities using two theoretical models: a one-dimensional spectroscopic model with Herman-Wallis rotation-vibration corrections, and a line-by-line ab initio dipole moment surface model [Zak et al. JQSRT 2016;177:31-42]. For the second approach, we fit only a single factor to rescale the theoretical integrated band intensity to be consistent with the measured intensities. We find that the latter approach yields an equally adequate representation of the fitted J-dependent intensity data and provides the most physically general representation of the results. Our recommended value for the integrated band intensity equal to 7.183 × 10−21 cm molecule−1 ± 6 × 10−24 cm molecule−1 is based on the rescaled ab initio model and corresponds to a fitted scale factor of 1.0069 ± 0.0002. Comparisons of literature intensity values to our results reveal systematic deviations ranging from −1.16 % to +0.33 %.

Fourier transform CO spectra near 1.6 μm

The absorption spectra of carbon monoxide have been recorded in the 6000–6450 cm−1 wavenumber regions using the Bruker IFS 125 HR Fourier transform spectrometer and a 30 m multipass cell with the White-type optical system. The spectra were recorded at spectral resolution of 0.008–0.012 cm−1, path length up to 1058 m, and at pressure range from 30 to 320 mbar. The temperature was about 301 K. The lines of the 3-0 bands of six isotopologues 12C16O, 13C16O, 12C18O, 12C17O, 13C18O, 13C17O and the lines of the hot 4-1 band of 12C16O were assigned in the spectra. The line intensities and the self-broadening coefficients were measured. In the case of the principal isotopologue the line intensities were determined for the lines with the angular momentum quantum number J up to 41. The effective dipole moment parameters describing the line intensities of the observed bands were fitted to the observed values of the line intensities. The uncertainty of the line intensity measurements for the strong unsaturated and unblended lines of the principal isotopologue varies between 2% and 2.5%. The comparison of our measured line intensities to those of other authors and of the HITRAN2016 database is given.

Probing electronic and atomic ensembles effects on PtAu3 nanoparticles with CO adsorption and electrooxidation

We have studied the adsorption and electrooxidation of CO on PtAu3 nanoalloys, aiming at providing further insight about the correlation between atomic structure and catalytic properties. The multiplicity of adsorption sites with different geometry and composition on the nanoparticles surface is demonstrated by a combination of electrochemical and infrared experiments. Specifically, the occurrence of low- and high-coordinated Pt atoms was confirmed by the splitting of the linearly-bonded CO band after removing CO from the electrolyte. Despite the low activity for the electrooxidation of COad of our PtAu3 nanoparticles, the combination of small Pt(111) terraces and small Pt atomic ensembles on their surfaces revealed by our experiments is connected with the negligible CO poisoning and the resulting high catalytic activity of our PtAu3 NPs for the formic acid oxidation reaction [Electrochim. Acta 2017, 224, 56–63].

Cluster Low-Streams Regression Method for Hyperspectral Radiative Transfer Computations: Cases of O2 A- and CO2 Bands

Current atmospheric composition sensors provide a large amount of high spectral resolution data. The accurate processing of this data employs time-consuming line-by-line (LBL) radiative transfer models (RTMs). In this paper, we describe a method to accelerate hyperspectral radiative transfer models based on the clustering of the spectral radiances computed with a low-stream RTM and the regression analysis performed for the low-stream and multi-stream RTMs within each cluster. This approach, which we refer to as the Cluster Low-Streams Regression (CLSR) method, is applied for computing the radiance spectra in the O2 A-band at 760 nm and the CO2 band at 1610 nm for five atmospheric scenarios. The CLSR method is also compared with the principal component analysis (PCA)-based RTM, showing an improvement in terms of accuracy and computational performance over PCA-based RTMs. As low-stream models, the two-stream and the single-scattering RTMs are considered. We show that the error of this approach is modulated by the optical thickness of the atmosphere. Nevertheless, the CLSR method provides a performance enhancement of almost two orders of magnitude compared to the LBL model, while the error of the technique is below 0.1% for both bands.

FTIR spectroscopy of three rovibrational bands of CO confined in silica aerogel: Molecule-surface collisions in nanoscale volumes

The absorption spectra of carbon monoxide confined in aerogel were recorded using Bruker IFS 125HR Fourier transform spectrometer within 2000–6500 cm−1 spectral range. The influence of degree of vibrational excitation on the line half-width for 1-0, 2-0 and 3-0 bands of CO confined in the same aerogel sample was studied for the first time. It was found that the character of obtained rotational dependencies is identical for all three bands and vibrational excitation insignificantly affects line HWHM.

Intermediate-mass Early-type Disk Galaxies in the Virgo Cluster. II. Near-Infrared Spectra and Evidence for Differences in Evolution* † ‡ † ‡

Abstract We discuss near-infrared (NIR) slit spectra of six early-type disk galaxies in the Virgo Cluster that were examined previously at visible/red wavelengths. Despite having similar intrinsic luminosities, colors, and morphologies, the NIR spectrophotometric properties of these galaxies indicate that they are not a homogeneous ensemble differing only in terms of luminosity-weighted age and metallicity. While the depth of the CO(2,0) band is consistent with the centers of these galaxies having solar or slightly sub-solar luminosity-weighted metallicities, galaxy-to-galaxy variations in the depth of the Na i 2.21 μm doublet are found, with Na i2.21 μm lines in three galaxies (NGC 4491, NGC 4584, and NGC 4620) that are deeper than those predicted for a solar chemical mixture and a solar-neighborhood mass function. In contrast, the Ca i2.26 μm triplet shows good galaxy-to-galaxy agreement but tends to be deeper than the model prediction. Considering the depth of the NaD lines, the deep Na i2.21 μm lines are tentatively attributed to a bottom-heavy mass function. This is counter to observed trends between mass function slope and velocity dispersion, and so the possibility of a super-solar [Na/Fe] is also discussed. Two of the three galaxies with deep Na i 2.21 μm (NGC 4584 and NGC 4620) have Sérsic exponents that are consistent with a classical bulge. As for NGC 4491, its central NIR spectrum contains prominent emission lines. The relative strengths of Brγ and H2S(1), the presence of [Fe ii] emission, and the mid-infrared spectral-energy distribution are all consistent with intense recent star formation near the center of that galaxy. The NIR spectrum of NGC 4584 is devoid of line emission in the NIR, suggesting that star formation does not power the emission detected at visible wavelengths from that galaxy. Wavelengths that contain the Ballick–Ramsey C2 band at 1.76 μm are matched by moderately metal-poor E-MILES model spectra with an age of 2 Gyr. The radial age trends in these galaxies are in the opposite sense to those in late-type disk galaxies, and it is concluded that they have evolved in a cluster environment for at least several Gyr.

Role of H2O for CO2 Reduction Reactions at Platinum/Electrolyte Interfaces in Imidazolium Room‐Temperature Ionic Liquids

AbstractCO2 reduction reactions (CO2RR) are interesting for power‐to‐x applications and have been studied on Pt electrodes in 1‐ethyl‐3‐methylimidazolium dicyanamide [EMIM][DCA] as well as in 1‐ethyl‐3‐methylimidazolium [EMIM][BF4], 1‐butyl‐3‐methylimidazolium [BMIM][BF4] and 1‐ocytl‐3‐methylimidazolium tetrafluoroborate [OMIM][BF4] electrolytes. Cyclic voltammetry indicates a strong increase in activity for CO2RR with water concentration, which was investigated on a molecular level by using IR absorption spectroscopy (IRAS) and sum‐frequency generation (SFG) to address both bulk and surface‐adsorbed species. IRAS demonstrates that the formation of an imidazolium carboxylic acid intermediate occurs at electrode potentials as high as −0.4 V, which depend on the choice of the RTIL and the water concentration. In addition, SFG spectroscopy provides evidence for the formation of CO on Pt atop sites and was used to determine the onset potential for the formation CO. In [BMIM][BF4] and [OMIM][BF4] electrolytes, the formation of CO is negligible even at very negative potentials of −1.5 V, but for [EMIM][DCA] and [EMIM][BF4] the formation of CO is observed and the onset potential shifts significantly with the H2O concentration. Taking the Stark tuning rate (40 cm−1/V) of the CO band into account, we conclude that the CO coverage is fairly low, yet the presence of CO leads to deactivation of the Pt surface and to a decrease in reduction currents.

Optimization of the OCO-2 Cloud Screening Algorithm and Evaluation against MODIS and TCCON Measurements over Land Surfaces in Europe and Japan

A method to tighten the cloud screening thresholds based on local conditions is used to provide more stringent schemes for Orbiting Carbon Observatory-2 (OCO-2) cloud screening algorithms. Cloud screening strategies are essential to remove scenes with significant cloud and/or aerosol contamination from OCO-2 observations, which helps to save on the data processing cost and ensure high quality retrievals of the column-averaged CO2 dry air mole fraction (XCO2). Based on the radiance measurements in the 0.76 μm O2A band, 1.61 μm (weak), and 2.06 μm (strong) CO2 bands, the current combination of the A-Band Preprocessor (ABP) algorithm and Iterative Maximum A Posteriori (IMAP) Differential Optical Absorption Spectroscopy (DOAS) Preprocessor (IDP) algorithm passes around 20%–25% of all soundings, which means that some contaminated scenes also pass the screening process. In this work, three independent pairs of threshold parameters used in the ABP and IDP algorithms are sufficiently tuned until the overall pass rate is close to the monthly clear-sky fraction from the MODIS cloud mask. The tightened thresholds are applied to observations over land surfaces in Europe and Japan in 2016. The results show improvement of agreement and positive predictive value compared to the collocated MODIS cloud mask, especially in summer and fall. In addition, analysis indicates that XCO2 retrievals with more stringent thresholds are in closer agreement with measurements from collocated Total Carbon Column Observing Network (TCCON) sites.

Spectroscopic Signatures of Pressurized Carbon Dioxide in Diffuse Reflectance Infrared Spectroscopy of Heterogeneous Catalysts

AbstractUsing diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to study surface species of reaction intermediates on heterogeneous catalysts requires particular precautions, when assigning IR bands to intermediates apparently resulting from the reaction of H2, CO, and CO2. In accordance with earlier work, it is shown that in the investigation of the heterogeneous methanol synthesis, several gas phase bands of CO2 were misassigned in previous studies as adsorbates on the catalyst surface. Thus, several combination bands and overtones of CO2 in the 2200–750 cm−1 range – notably those at 2130, 2112, 2107, 2094, 2077, ∼2056, 1933, ∼1920, ∼1079, ∼1050, ∼973, and ∼948 cm−1 – were already misinterpreted as adsorbates/intermediates. Some of these bands exhibit similar (low) intensities as surface species and are in the range of typical adsorbed CO or methoxy/methanol vibrations. Higher pressures and temperatures, which are necessary to study industrial catalysts by in situ IR spectroscopy, even amplify this effect. In addition, due to a Fermi resonance at a CO2 partial pressure above ∼10 bar, two further bands appear at 1388 and 1285 cm−1. This is also within the range typically associated with surface adsorbates. In order to avoid misassignments of IR bands for in situ or operando DRIFT spectroscopy, those occurring at CO2 pressures up to 30 bar in the widely used Praying MantisTM High Temperature Reaction Chamber are presented here and assigned to their origin as combination bands and overtones of gaseous CO2.

Zr-based metal–organic frameworks drived Rh–Mn catalysts for highly selective CO hydrogenation to C2 oxygenates

A series of Zr-based metal-organic frameworks (UiO-66) supported Rh–Mn catalysts with various metal loadings were prepared by using a co-impregnation method, and the catalytic activities were investigated for the direct synthesis of ethanol-based C2+ oxygenates from CO hydrogenation. The catalysts were comprehensively characterized by means of N2 sorption, XRD, TEM, XPS, H2-TPR, and DRIFT. The structural and textural properties of the catalysts show clearly that the overall framework structure of UiO-66 can be beneficial to the high dispersion of supported metals, but the synergistic effect of Rh and Mn would be influenced by the metal loading or Mn/Rh ratio. When the loadings of Rh and Mn reached 3 wt.% and 3 wt.%, the catalyst has the best catalytic activity with the highest yield of C2+ oxygenates of 200.1 g/(kg h), which can be attributed to the enhanced CO dissociation ability of Rh sites and weaker Rh−CO band strength.

Vibrational shifts of absorption bands of linear molecules diluted in high-density rare gases: Measurements and modeling for CO2-Rg and OCS-Rg

Increase of buffer gas pressure causes redistribution of intensity in the IR absorption bands and, indicating the presence of vibrational perturbation, changes the first spectral moment value responsible for the band-origin position. Band-origin shift coefficients for the ν3, 2ν3 and ν2 bands of OCS and the ν3 band of CO2 diluted in high-density Ar, Kr and Xe are measured and calculated by two methods: directly with available in the literature vibrationally dependent potential-energy surfaces for both initial and final vibrational states and assuming that vibrational dependence arises from the interaction of the permanent /transient dipole moment of the absorbing molecule and the dipole moment induced on the perturber. A comparative analysis of results is given, showing a general underestimation of calculations with respect to measurements.

Evidence of an evolved nature of MWC 349A

ABSTRACT The Galactic emission-line object MWC 349A is one of the brightest radio stars in the sky. The central object is embedded in an almost edge-on oriented Keplerian rotating thick disc that seems to drive a rotating bipolar wind. The dense disc is also the site of hot molecular emission such as the CO bands with its prominent band heads in the near-infrared spectral range. Despite numerous studies, the nature of MWC 349A is still controversial with classifications ranging from a pre-main sequence object to an evolved supergiant. We collected new high-resolution near-infrared spectra in the K and Lbands using the GNIRS spectrograph at Gemini-North to study the molecular disc of MWC 349A, and in particular to search for other molecular species such as SiO and the isotope 13CO. The amount of 13CO, obtained from the 12CO/13CO ratio, is recognized as an excellent tool to discriminate between pre-main-sequence and evolved massive stars. We find no signatures of SiO band emission, but detect CO band emission with considerably lower intensity and CO gas temperature compared to previous observations. Moreover, from detailed modelling of the emission spectrum, we derive an isotope ratio of 12CO/13CO = 4 ± 1. Based on this significant enrichment of the circumstellar environment in 13CO, we conclude that MWC 349A belongs to the group of B[e] supergiants, and we discuss possible reasons for the drop in CO intensity.

An active and stable nickel-based catalyst with embedment structure for CO2 methanation

The CO2 methanation catalyst with high activity and stability has attracted significant attention from industrial and academic community. In this work, a highly active and stable Ni@HZSM-5 catalyst was synthesized by hydrothermal method using conventional Ni/SiO2 catalyst as unique silicone source. The Ni@HZSM-5 showed high activity and excellent stability during 40 h CO2 methanation reaction, comparing to the conventional Ni/SiO2 and Ni/HZSM-5 catalysts prepared by impregnation method. After a prolonged reaction, the Ni@HZSM-5 still maintain similar nickel content and the structure of active nickel to fresh catalyst, due to the special embedment structure. Meanwhile, it is found that the nickel active phase of the Ni@HZSM-5 catalyst donates more electrons to zeolite, resulting in higher BE values, lower wavenumber and weak intensity of CO bands. Hence, the Ni@HZSM-5 catalyst can prevent the formation of volatile metal-molecule intermediates (gaseous Ni(CO)x), which resulted in serious sintering and loss of the supported nickel in conventional Ni catalysts. All obtained catalysts were characterized by XRD, SEM-EDS, TEM, XRF, BET, TGA, in situ CO-DRIFTS and in situ XPS.

Spectral sizing of a coarse-spectral-resolution satellite sensor for XCO<sub>2</sub>

Abstract. Verifying anthropogenic carbon dioxide (CO2) emissions globally is essential to inform about the progress of institutional efforts to mitigate anthropogenic climate forcing. To monitor localized emission sources, spectroscopic satellite sensors have been proposed that operate on the CO2 absorption bands in the shortwave-infrared (SWIR) spectral range with ground resolution as fine as a few tens of meters to about a hundred meters. When designing such sensors, fine ground resolution requires a trade-off towards coarse spectral resolution in order to achieve sufficient noise performance. Since fine ground resolution also implies limited ground coverage, such sensors are envisioned to fly in fleets of satellites, requiring low-cost and simple design, e.g., by restricting the spectrometer to a single spectral band. Here, we use measurements of the Greenhouse Gases Observing Satellite (GOSAT) to evaluate the spectral resolution and spectral band selection of a prospective satellite sensor with fine ground resolution. To this end, we degrade GOSAT SWIR spectra of the CO2 bands at 1.6 (SWIR-1) and 2.0 µm (SWIR-2) to coarse spectral resolution, without a further addition of noise, and we evaluate single-band retrievals of the column-averaged dry-air mole fractions of CO2 (XCO2) by comparison to ground truth provided by the Total Carbon Column Observing Network (TCCON) and by comparison to global “native” GOSAT retrievals with native spectral resolution and spectral band selection. Coarsening spectral resolution from GOSAT's native resolving power of >20 000 to the range of 700 to a few thousand makes the scatter of differences between the SWIR-1 and SWIR-2 retrievals and TCCON increase moderately. For resolving powers of 1200 (SWIR-1) and 1600 (SWIR-2), the scatter increases from 2.4 (native) to 3.0 ppm for SWIR-1 and 3.3 ppm for SWIR-2. Coarser spectral resolution yields only marginally worse performance than the native GOSAT configuration in terms of station-to-station variability and geophysical parameter correlations for the GOSAT–TCCON differences. Comparing the SWIR-1 and SWIR-2 configurations to native GOSAT retrievals on the global scale, however, reveals that the coarse-resolution SWIR-1 and SWIR-2 configurations suffer from some spurious correlations with geophysical parameters that characterize the light-scattering properties of the scene such as particle amount, size, height and surface albedo. Overall, the SWIR-1 and SWIR-2 configurations with resolving powers of 1200 and 1600 show promising performance for future sensor design in terms of random error sources while residual errors induced by light scattering along the light path need to be investigated further. Due to the stronger CO2 absorption bands in SWIR-2 than in SWIR-1, the former has the advantage that measurement noise propagates less into the retrieved XCO2 and that some retrieval information on particle scattering properties is accessible.

Origin of the High CO Oxidation Activity on CeO2 Supported Pt Nanoparticles: Weaker Binding of CO or Facile Oxygen Transfer from the Support?

AbstractPt clusters supported on CeO2 are highly active for low temperature CO oxidation. The enhanced reactivity could be caused by weakening of the CO binding on Pt, allowing adsorbed oxygen to more effectively compete for sites. An alternative explanation is that interfacial sites allow adsorbed CO on Pt to react with lattice oxygen in the ceria. Here we explore the origins of enhanced CO oxidation reactivity on Pt/CeO2 using in‐situ/operando infrared and x‐ray spectroscopies, microcalorimetry, and reaction kinetics. We show that CO adsorbs strongly (∼110–120 kJ/mol) on Pt clusters (∼1.5 nm) and Pt is almost fully covered by CO during reaction, indicating that the high activity can be related to reactive interfacial O* species. Using in‐situ infrared spectroscopy we show that when the reaction mixture of CO and O2 stops flowing over the catalyst, the adsorbed CO on Pt is lost since it reacts with interfacial O*, but if this O* is depleted, the CO band does not disappear. The role of CeO2 is not to alter the binding of CO, but rather to enhance the reactivity of the interfacial metal‐support lattice oxygens. The reaction mechanism involving the interfacial Pt−CeO2 sites (two‐site mechanism) is further confirmed by kinetic measurements which show near zero order dependence on CO and O2 partial pressures.

Mid-IR spectra of the M-type Mira variable R Tri observed with theSpitzerIRS

ABSTRACTWe present analysis of mid-infrared (IR) spectra of the oxygen-rich Mira variable R Tri. The data were taken with the Spitzer Infrared Spectrometer (IRS) as part of a study tracking how Mira variables’ regular pulsations affect circumstellar envelopes. We detected strong emission lines at 13.87, 16.18, and 17.6 $\hbox{$\mu $m}$, and one strong absorption feature at 14.98 $\hbox{$\mu $m}$. The emission features at 13.87 and 16.18 $\hbox{$\mu $m}$ are excited vibrational bands of CO2, while the absorption feature is the fundamental ν2 band. The 17.6 $\hbox{$\mu $m}$ emission feature has a completely different character than the molecular lines and we report its identification as Fe i fluorescence. We used a two-slab model with the radiative transfer code radex to model the CO2 Q-branch bandheads. Our results indicate a slab of gas with T∼600 K located at ∼3–4 R*. The cool temperature discrepancy with the radius provides observational evidence for the previously theoretical ‘refrigeration zone’.

Optical frequency comb-based cavity-enhanced Fourier-transform spectroscopy: Application to collisional line-shape study

Direct-comb spectroscopy techniques uses optical frequency combs (OFCs) as spectroscopic light source. They deliver high sensitivity, high frequency resolution and precision in a broad spectral range. Due to these features, the field has burgeoned in recent years. In this work we constructed an OFC-based cavity-enhanced Fourier-transform spectrometer in the near-infrared region and used it for a line-shape study of rovibrational transitions of CO perturbed by Ar. The highly sensitive measurements spanned the wavenumber range from 6270 cm−1 to 6410 cm−1, which covered both P and R branch of the second overtone band of CO. The spectrometer delivers high-resolution surpassing the Fourier-transform resolution limit determined by interferogram length, successfully removing ringing and broadening effects caused by instrumental line shape function. The instrumental-line-shape-free method and high signal-to-noise ratio in the measurement allowed us to observe collisional effects beyond those described by the Voigt profile. We retrieved collisional line-shape parameters by fitting the speed-dependent Voigt profile and found good agreement with the values given by precise cavity ring-down spectroscopy measurements that used a continuous-wave laser referenced to a stabilized OFC. The results demonstrate that OFC-based cavity-enhanced Fourier-transform spectroscopy is a strong tool for accurate line-shape studies that will be crucial for future spectral databases.

Photodissociation branching ratios for several absorption bands of 12C16O from 108,500 to 109,220 cm−1

In the present study, photodissociation branching ratios are measured with optimised experimental conditions for the 12C16O absorption bands with upper states of I′(5sσ) 1Σ+(v′ = 1), (6sσ) 1Σ+(v′ = 0) and (6pπ) 1Π(v′ = 0), which were not observed in the recent study covering the titled energy range (J. Chem. Phys. 137, 034305 (2012)). The absorption band with the upper state of (6pσ) 1Σ+(v′ = 0) has been reinvestigated, and a weak dependence of branching ratios into the spin-forbidden channels on the rotational quantum number is observed. In addition to these relatively strong absorption bands, two weak bands have also been identified in the C+ ion photofragment spectra, one with well rotationally resolved 1Π character and has never been observed before, and the other with diffuse structure and its upper state was assigned as C′1Σ+(v′ = 9) before in spectroscopic studies. Except for the two newly observed weak absorption bands, the four strong absorption bands all predominantly dissociate into the ground channel C(3P)+O(3P). By far, we have finished measuring the photodissociation branching ratios for all the strong 12C16O absorption bands of astrophysical importance above the photon energy of 102,700 cm−1.

The Ethylene-Carbon Dioxide Complex and the Double Rotor Model.

The infrared spectrum of the weakly bound C2H4-CO2 complex is investigated in the region of the ν3 fundamental band of CO2 (≈2350 cm-1), using a tunable OPO laser source to probe a pulsed supersonic slit jet expansion. The spacing of the various K-subbands in this perpendicular (ΔK = ±1) spectrum is very irregular, and the pattern of irregularity is quite different from that observed previously in another C2H4-CO2 band by Bemish et al. [ J. Chem. Phys. 1995 , 103 , 7788 ]. But by allowing for the different symmetry of the ν3 (CO2) upper vibrational state, both results can be strikingly well explained using the "double internal rotor" model as described by Bemish et al.

Analysis of the first overtone bands of isotopologues of CO and SiO in stellar spectra

Context.This study is based on models of the first overtone (Δv= 2) bands of the monosubstituted isotopologues of CO at 2.3μm in the spectrum of Arcturus (K2 III) and of the monosubstituted isotopologues of SiO at 4μm in the spectrum of the red giant HD 196610 (M6 III).Aims.We aim to investigate problems involving the computation of the first overtone bands of isotopologues of CO and SiO in the spectra of late-type stars and to determine isotopic abundances.Methods.We used fits of theoretical synthetic spectra to the observed stellar molecular bands of CO and SiO for determining the abundances for isotopes of C, O, and Si.Results.Fits of synthetic spectra of the12C16O first overtone bands at 2.3μm computed with three available line lists to the observed spectrum of Arcturus provide the same carbon abundance [C] = − 0.6 and isotopic ratio of carbon12C/13C = 10 ± 2. However, the quality of fits to the observed spectrum differ for three line lists used. Furthermore, the derived oxygen isotopic ratio16O/18O = 2000 ± 500 is larger than that known in the solar system, where16O/18O = 500. The silicon isotopic ratio in the atmosphere of the red giant HD 196610 has been revised. Using the ExoMol SiO line list with appropriate statistical weights for the SiO isotopologues, the “non-solar” ratio28Si:29Si:30Si = 0.86 ± 0.03:0.12 ± 0.02:0.02 ± 0.01 is obtained.Conclusions.We find that: (a) the computed isotopic carbon and silicon ratios determined by the fits to the observed spectrum depend on the adopted abundance of C and Si, respectively; and (b) Correct treatment of the nuclear spin degeneracies parameter is of crucial importance for today’s application of HITRAN and ExoMol line lists in the astrophysical computations.