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© 2021 The Author(s)The rotational structure of the A1Π(v = 2) level of 12C18O is re-examined using high-accuracy experimental data comprised of 541 molecular lines obtained by two complementary Fourier-transform techniques. The absorption spectrum of the A1Π – X1Σ+(2, 0) band, in the range 66,500 - 67,650 cm–1, was recorded by the vacuum-ultraviolet FT spectrometer at the DESIRS beamline of the SOLEIL synchrotron. Visible emission spectra of the B1Σ+ – A1Π(0, 2) and C1Σ+ – A1Π(0, 2) bands in the range 19,200 - 20,000 and 24,300 - 24,800 cm–1 were obtained with a Bruker IFS-125HR spectrometer at the University of Rzeszow. The absolute accuracy of line frequencies are 0.01 and 0.005 - 0.01 cm−1, respectively. Results from the B1Σ+ – X1Σ+(0, 0) and C1Σ+ – X1Σ+(0, 0) absorption bands of 12C18O were added to the experimental data set. A deperturbation analysis of A1Π(v = 2) is performed with an effective Hamiltonian and a term-value fitting approach. Accurate molecular constants for A1Π(v = 2) and the e3Σ–(v = 4), d3Δ(v = 7), aʹ3Σ+(v = 12) and I1Σ–(v = 3) perturbing levels were determined. Perturbation parameters of the spin-orbit A1Π(v = 2) ~ [e3Σ–(v = 4), d3Δ(v = 7), aʹ3Σ+(v = 12)] and rotation-electronic (L-uncoupling) A1Π(v = 2) ~ [I1Σ–(v = 3, 4), D1Δ(v = 3)] interactions, were obtained. A significant, indirect influence of the a3Π state on the A1Π state was detected in 12C18O and has therefore been included in the final fit by taking into account the simultaneous a3Π(v = 13) ~ [e3Σ–(v = 4), d3Δ(v = 7), aʹ3Σ+(v = 12)] ~ A1Π(v = 2) spin-orbit/spin-electronic/L-uncoupling and spin-orbit interactions as well as the a3Π(v = 13) ~ [D1Δ(v = 3), I1Σ–(v = 3)] ~ A1Π(v = 2) spin-orbit and L-uncoupling interactions. This work results in determination of 110 rotational term-values for the A1Π(v = 2) state and its perturbers.

This study is a continuation of experimental efforts on the analysis of the near-infrared absorption spectrum of water vapor. Our previous studies were focused on water vapor in natural isotopic abundance. Now we are interested in the H218O water isotopologue. New spectra of water samples enriched by 18O were recorded between 6400 and 9400 cm−1 in Reims with the Connes-type Fourier Transform Spectrometer, built in our laboratory. The spectra were recorded at room temperature with a H218O abundance enrichment of about 95% and a non apodized resolution of 0.010 cm−1. Pressure varied from 2 to 13 torr and the absorption path length was from 67 cm to 1001 m. This article presents the results of the analysis of the first part of the whole recorded spectral range below 8000 cm−1. About 8100 absorption lines were found in the recorded spectra with an absorption path length from 8 to 88 m between 6525 and 8011 cm−1. Overall, 7993 lines were assigned to 8647 transitions of six water isotopologues (H216O, H217O, H218O, HD16O, HD17O, and HD18O). Ninety-eight lines with intensity values between 6 × 10−27 and 1.45 × 10−25 cm/molecule were left unassigned. More than 870 H218O, H217O and HD18O lines were observed for the first time. The observed line positions allow to obtain about 90 new or corrected rotation-vibration energy levels of H218O and H217O. Comparison of line positions and intensities with literature data are presented and discussed. Some examples of disagreements between the measurements and data from the literature are presented in the last part of this article.

The MERLIN mission (MEthane Remote LIdar missioN) is a space mission dedicated to the methane atmospheric retrieval based on absorption LIDAR measurements at nadir. The methane columns will be obtained by difference between the LIDAR signal at the on-line wavelength corresponding to the R(6) manifold of the 2ν3 band of methane at 6077 cm−1 and the off-line signal at a wavenumber about 1 cm−1 below. As atmospheric water vapor lines may affect the methane retrievals, the present study is dedicated to a detailed laboratory characterization of the interfering water vapor absorption in the targeted region. To this aim, high sensitivity absorption spectra of pure water vapor and water vapor in air are recorded at room temperature using a cavity ring down spectrometer (CRDS) combined with a self-referenced frequency comb. The CRDS recordings cover the 6071.4–6080.0 cm−1 interval with a noise equivalent absorption, αmin, on the order of 5 × 10−11 cm−1 for a 10−3 cm−1 sampling of the spectra. The measured pure and air-broadened spectra are analyzed using the Nelkin-Ghatak (NG) or the speed-dependent Nelkin-Ghatak (sdNG) profile. A multi-spectrum fitting procedure in which series of spectra recorded at different pressures (between 0.7 and 12 Torr for pure water vapor and between 100 and 700 Torr for H2O in air) are simultaneously adjusted, is used to retrieve the spectroscopic parameters. Accurate line parameters including self- and air-pressure shifts, self- and air-broadenings, Dicke narrowing and the speed-dependent coefficients are determined for most of the lines with intensity larger than 10−28 cm/molecule at 296 K. The list is complemented with literature data (in particular from the HITRAN database) to be complete down to a 10−29 cm/molecule intensity cut-off. The obtained spectroscopic results are discussed in comparison with literature data.

The absorption spectrum of nitrous oxide around 1.56 µm has been recorded with Doppler limited resolution by a continuous-wave cavity ring-down spectrometer at room temperature using 15N-enriched samples. The typical sensitivity was at the level of 2 × 10−10 cm−1. In total, 3389 transitions were observed and ro-vibrationally assigned on the basis of the global effective Hamiltonian model for six nitrous oxide isotopologues (14N15N16O, 15N14N16O, 14N15N18O, 15N14N18O, 14N15N17O and 15N14N17O). The band-by-band analysis led to the determination of ro-vibrational parameters of 47 bands, 36 of them were newly observed, and the rotational analysis of 11 others were significantly extended and improved. New sets of the effective Hamiltonian parameters were determined for the 14N15N16O and 15N14N16O isotopic species.

The high resolution absorption spectrum of the NO2 molecule is recorded between 5855 and 6006 cm−1 by high sensitivity cavity ring down spectroscopy (CRDS). Positions and intensities in the 5 × 10−27 − 4 × 10−23 cm/molecule range are derived from the profile fitting of more than 6900 lines. The absorption is dominated by the transitions of the (103)–(000) vibrational band centered at 5984.704 cm−1. The spectrum is assigned and modeled using an effective Hamiltonian (EH) which explicitly takes into account a spin–rotational interaction and interaction of the (103) bright state with three “dark” states: (122), (080) and (410). The ν1 + 3ν3 band was already analyzed by Fourier transform spectroscopy (FTS) in Miljanic S., Perrin A., Orphal J., Fellows C.E., Chelin, J. Mol. Spectrosc. 2008, V. 251, P. 9–15, where resonance interactions between the (103) state and the (122) and (080) “dark” states were taken into account. More than 3000 lines are presently assigned with rotational quantum numbers N and Ka up to 59 and 13, respectively, while 1147 transitions with maximum N and Ka values of 47 and 8, respectively, were previously identified by FTS. The measured line positions are reproduced with an (obs.-calc.) rms of 0.0023 cm−1 by variation of 41 EH parameters. About 80 transitions reaching the (080) highly excited bending upper state and borrowing their intensity from the resonance coupling with the (103)–(000) band were assigned for the first time. The main parameter in the transition moment series of the ν1 + 3ν3 band is determined from the fitting of the measured intensities.

Absorption of light by a free standing monolayer of monodisperse crystalline silicon (c-Si) spherical particles is investigated using the quasicrystalline approximation (QCA) of the theory of multiple scattering of waves. The simulation results for the partially ordered monolayer and the highly ordered monolayer with imperfect triangular lattice are presented in the ranges of particle diameters from 0.05 µm to 1 µm, monolayer filling factors from 0.1 to 0.7, and wavelengths of incident light from 0.3 µm to 1.12 µm. The spatial pattern of a monolayer affects the absorption coefficient most strongly when the particle sizes are comparable with the wavelength. The spatial-order-induced peaks in the absorption spectra of a highly ordered monolayer are studied. The spectral absorption by such a monolayer can be more than 30 times greater than that of the partially ordered monolayer in the narrow wavelength intervals. The integrated over the terrestrial solar spectral irradiance “Global tilt” ASTM G173-03 absorption coefficient is analyzed. In the wavelength range of 0.3 µm ≤ λ ≤ 1.12 µm the integral absorption can be almost twice as large as that for the partially ordered monolayer. In the wavelength range of small absorption index of c-Si (0.8 µm ≤ λ ≤ 1.12 µm) the integral absorption coefficient of highly ordered monolayer can be more than 10 times greater than for the partially ordered monolayer.

An optically accessible gas cell has been designed, manufactured, and tested for the purpose of enabling spectroscopic measurements in the mid-wave infrared at both high pressures and high temperatures. The water-cooled inconel cell has been tested to sustain pressures over 200 atm or operating temperatures above 1200 K. Interchangeable sapphire or calcium-fluoride rods, transmissive up to 8 µm in wavelength, are used to span the thermal gradients at the edge of the heating zone, providing for a low-temperature seal on one end and access to a thermally uniform test section on the other. In this paper, we detail the cell design and validation testing, while highlighting cell capabilities with laser absorption measurements of gas spectra in the 2–8 µm domain at high-pressure ( > 100 atm) and high-temperature ( > 1200 K) conditions. The maximum cell pressure and temperature reached simultaneously was 102 atm and 1030 K. Non-ideal spectroscopic phenomena (e.g. line mixing) are revealed at the extreme conditions investigated.

The absorption spectra of the mixture of SO2 and CO2 at different partial pressures of both gases have been recorded at room temperature in the 4 µm region using the Bruker IFS 125 HR FTIR spectrometer. The multispectrum fitting procedure has been applied to these spectra to recover the CO2-broadening and shift parameters of the sulfur dioxide spectral lines. The CO2 broadening and the pressure induced shift coefficients for 1422 and 116 lines of the ν1 + ν3 A-type band of 32S16O2 and 34S16O2, respectively, have been derived. Beside, these coefficients have been derived for 254 lines of the ν1 + ν2 + ν3 − ν2 hot band of 32S16O2. The rotational dependence of the values of these coefficients is discussed. The CO2 pressure induced shift coefficients for this molecule are published for the first time. The comparison of the obtained broadening coefficients to those published by other authors for one pure rotational line and for the lines of the ν1 B-type band is given.

Absorption cross-sections of 1,1,1,2,3,3-hexafluoropropane (HFC-236ea) and 1,1,2,2, 3-pentafluoropropane (HFC-245ca) were derived from Fourier transform infrared spectra recorded from 550 to 3400 cm − 1 with a resolution of 0.1 cm − 1 over a temperature range of 300–365 K. Good agreement was found between the experimentally derived results, theoretical spectra from density functional theory (DFT) calculations, and previously published experimental measurements. The only temperature dependence observed was in the amplitude of some of the absorption peaks due to the changing ratio of the stable conformations of both molecules studied. This temperature dependence does not result in a significant trend in integrated band strength as a function of temperature. The average value for the integrated band strength of HFC-236ea was found to be (1.982 ± 0.012)x10 − 16 cm molecule − 1 over the spectral range of 550 to 3026 cm − 1 . The average value for the integrated band strength of HFC-245ca was found to be (1.348 ± 0.35)x10 − 16 cm molecule − 1 over the spectral range of 570 to 3035 cm − 1 . Radiative efficiency (RE) and the global warming potential (GWP) for both molecules were also derived, accounting for corrections due to atmospheric lifetimes and stratospheric temperature adjustment. A RE of 0.256 ± 0.034 Wm − 2 ppbv − 1 was obtained for HFC-236ea, which leads to a GWP100 of 1141 ± 402 for 550–3000 cm − 1 . For HFC-245ca, a RE of 0.197 ± 0.023 Wm − 2 ppbv − 1 was derived, which leads to a GWP100 of 588 ± 205 for 550–3000 cm − 1 . The DFT calculation was linearly adjusted to match the experimental spectrum. Using this adjusted DFT spectrum to expand the range below 550 to 0 cm − 1 increases the RE to 0.265 ± 0.035 Wm − 2 ppbv − 1 and the GWP100 to 1181 ± 417 for HFC-236ea; while for HFC-245ca, the RE increases to 0.202 ± 0.027 Wm − 2 ppbv − 1 and the GWP100 to 602 ± 210.

A framework for the study of high-temperature hydrocarbon pyrolysis is presented. The proposed framework details a multi-wavelength speciation method using convex optimization, a review of complementary fixed-wavelength laser diagnostics, and a database of high-temperature absorption cross-sections to enable use of the framework for 11 different species. The proposed speciation method involves a vectorized Beer-Lambert system solved under solution constraints using convex optimization. In support of the proposed method, a review of pertinent laser diagnostics and a database of high-temperature absorption cross-sections are also provided. The database includes measured absorption cross-sections of methane (CH4), ethylene (C2H4), propene (C3H6), isobutene (i-C4H8), 1-butene (1-C4H8), benzene (C6H6), toluene (C7H8), and four jet fuels (samples of Jet A, JP5, JP8, and Gevo ATJ) at the wavelengths of 3.1758 µm, 3.17595 µm, 3.283 µm, 3.392 µm, 3.410 µm, 10.532 µm, 10.675 µm, 10.89 µm, 10.958 µm, 10.962 µm, and 11.345 µm within the range of 300–1600 K and 0.25–4 atm. The database is comprised of over 1000 high–temperature absorption cross-section measurements from new shock tube experiments, new Fourier transform infrared spectrometer (FTIR) experiments, and an aggregated dataset from the literature. The convex speciation method and cross-section database provided will facilitate laser absorption studies of hydrocarbon pyrolysis used in the development of chemical kinetic mechanisms.

International audience; A collision induced absorption (CIA) band has been measured near 6000 cm$^{-1}$ in a spectrum of humidified CO$_2$ recorded by cavity ring down spectroscopy (CRDS) at low pressure (

A methodology was recently developed with a broad-tuning, rapid-scan external-cavity quantum-cascade-laser in conjunction with shock tube facilities to measure the high-temperature mid-infrared absorption spectra of gaseous molecules. This technique is deployed to measure the cross section profiles in the C-O stretching band for methanol (CH3OH) and ethanol (C2H5OH) between 930 and 1170 cm-1. Methanol spectra are presented from 620 to 1304K between 0.98-3.30 atm with distinctive P, Q, and R branches of the ν8 vibrational band. At elevated temperatures, the emergence of hotbands and high-J ro-vibrational transitions are clearly observed. The absorption cross sections of ethanol are measured from 296 to 1018K between 0.90-3.27 atm. The peak strength decreases with temperature, with the peak location shifting to lower wavenumbers. These measurements are compared with existing empirical models, illustrating a strong need for the development of a high-temperature spectroscopic database.

Linestrengths, self-broadening and narrowing coefficients for 8 absorption transitions of CO2 near 1.43 µm were measured using the wavelength modulation direct absorption spectroscopy (WM-DAS) at 300–1000 K and 5–20 kPa. The SNR was enhanced to 1500 for the peak absorbance around 5% at room temperature and remains at 550 for the peak absorbance around 1% at high temperatures by use of the WM-DAS method. The Voigt, Rautian, Galatry and quadratic speed-dependent Voigt profiles were used to recover the absorbance and retrieve the best-fit spectroscopic parameters and their temperature dependence. The quadratic speed-dependent Voigt profile was found to give the best combination of accuracy and robust lineshape parameters. The measured linestrengths and self-broadening coefficients compare well with the available values listed in the HITRAN/HITEMP database. The self-narrowing coefficients were also determined for GP, RP and qSDVP with analyses of the uncertainties in these spectroscopic parameters.

A methodology for the measurement of mid-infrared absorption cross sections of gaseous molecules at high temperatures and pressures is presented. A rapid-tuning, broad-scan external cavity quantum cascade laser with a tuning rate in excess of 30000 cm − 1 s − 1 has been employed in the measurement of full vibrational bands ( > 100 cm − 1 ) in shock-heated test gases. The approach is demonstrated with measurements of the absorption cross section of ethylene (C2H4) in the 8.5 µm to 11.7 µm region for temperatures from 800 K to 1600 K and pressures from 1 to 5 atm. Decreasing peak strength with temperature is observed as well as pressure-insensitivity. The measurements are compared with existing experimental, empirical, and ab initio databases. Additionally, illustrative absorption cross section measurements of propene (C3H6), 1-butene (1-C4H8), 2-butene (2-C4H8), 1,3-butadiene (1,3-C4H6), and methanol (CH3OH) are presented near 1000 K and 2.3 atm.

Well-ordered films of silver sulfide (Ag2S) nanoparticles (NPs) embedded in the matrix of poly vinyl alcohol (PVA) were fabricated using Successive Ionic Layer Adsorption and Reaction (SILAR) technique. Enlarging the size and increasing the concentration of Ag2S NPs by increasing the number of SILAR cycles confirmed by surface scanning electron microscopy (SEM) images of the produced films. The material composition was studied using energy dispersive X-ray (EDX) analysis. UV-visible experimental spectra of samples were compared with discrete dipole approximation (DDA) calculations results and good agreements were achieved. Increasing the number of peaks and valleys and redshift of peaks by increasing the number of SILAR cycles were obviously observed from the results. The most interesting conclusion of this work raised from electric near-field contour distributions investigations and implies that a matrix of insulator material (PVA) can cause an asymmetry in the intensity distribution of electric field around Ag2S NPs and let more dipole oscillations happen and more peaks appear in extinction/absorption spectra. (C) 2018 Elsevier Ltd. All rights reserved.

The absorption spectrum of water vapor enriched in oxygen-17 has been recorded by a continuous-wave cavity ring-down spectrometer (CW-CRDS) at room temperature in the 12,277–12,894 cm−1 region. The typical sensitivity of 2 × 10−10 cm−1 allowed the detection of water vapor transitions with intensities larger than 1 × 10−28 cm−1/(molecule cm−2). In total, more than 3400 lines were observed in the recorded spectra with a typical frequency accuracy of 0.002 cm−1. In which more than 3400 transitions were ro-vibrationally assigned to five water isotopic species (H217O, H216O, H218O, HD16O, and HD17O) using the known empirical energy levels combined with the calculated variational line lists based on the results of Partridge and Schwenke. About 1300 transitions of H217O were assigned, leading to the determination of new energy levels of 17 vibration states. Those assigned H217O transitions are involved with the upper vibration states of (013), (023), (032), (051), (061), (070), (080), (090), (112), (131), (150), (160), (211), (230), (301), (310), and (320). The maximum values of the rotational numbers J and Ka were 16 and 9, respectively. The 5ν1 band of HD17O was assigned for the first time as well. The line positions and energy levels determined in this work were compared with literature, and it shows a significant improvement of the line positions of H217O and HD17O in the 12,277–12,894 cm−1 region.

In the context of climate change mitigation, reuse of carbon dioxide (CO2) represents an alternative with important applications in chemical industry and power generation. For this purpose, CO2 must be purified. Combustion processes lead to high amounts of CO2 but still with impurities and also accompanied by toxic gases (mainly NO and CO). A catalytic reduction process of NO (to N2) while oxidizing CO into CO2 is a promising method to purify the CO2. However, nitrous oxide (N2O) with a global warming potential of 300 times greater than CO2 may be a by-product from this process. It is therefore necessary to optimize the chemical reaction conditions to minimize N2O production. A room-temperature continuous-wave (CW) external cavity quantum cascade laser (EC-QCL)-based optical sensor was developed for real-time monitoring N2O production during the whole catalytic reaction process. A well-isolated N2O absorption line, located at 1261.0598 cm−1, of the ν1 fundamental vibrational band was selected for sensitive and selective measurement of N2O concentration by direct absorption spectroscopy. Using a modified-Herriot multi-pass cell with an effective path-length of 50 m, the limit of detection (1σ) of 32.3 ppbv was obtained in 12 s with 1.1% relative uncertainty in measurement precision. N2O productions through the catalytic reduction of NO by CO over Pt/SiO2 catalyst under different temperatures were investigated. High N2O production of up to ∼6.1 ppmv at 190 °C was observed. The optimal reaction conditions for zero N2O production were found at a temperature higher than 340 °C where 47% of NO was converted to N2.

The absorption spectra of a mixture of CO with CO2 at different partial pressures of CO2 have been recorded at room temperature in the 2000–2300 cm−1 region using a Bruker IFS 125 HR FTIR spectrometer. To obtain the spectral line parameters for the fundamental band of CO molecule, the quadratic speed-dependent Voigt profile was used for the first time. The CO2 pressure induced broadening and shift coefficients for 49 spectral lines have been measured. A comparison with the published data is discussed.

Ab initio multiconfiguration Dirac–Hartree–Fock (MCDHF) calculations have been carried out in order to determine the isotope shift (IS) electronic parameters of transitions belonging to electric dipole (E1) transition arrays 5 s 2 5 p 3 − 5 s 2 5 p 2 6 s , 5 s 2 5 p 2 6 s − 5 s 2 5 p 2 6 p and 5 s 2 5 p 2 6 s − 5 s 2 5 p 2 7 p in neutral antimony, Sb I. In a correlation model limited to single and double excitations from the valence shells, these parameters, combined with the changes in mean-square nuclear charge radius δ⟨r2⟩123,121 compiled by Angeli and Marinova [3] produce isotope shifts values in good agreement with the most recent measurements by high-resolution emission and optogalvanic absorption spectroscopy of Sobolewski et al. [5] but not with the old measurements of Buchholz et al. [4] for 5 p 3 − 5 p 2 6 s . However, our analysis does not allow to reject the latter due to the large uncertainty affecting δ⟨r2⟩123,121, i.e. 0.072 ± 0.048 fm2 [3]. This shows the need of a more accurate determination of this nuclear parameter. Although improving excitation energies, the inclusion of core-valence correlation limited to one hole in the 4d core subshell destroyed the theory-experiment agreement on the IS parameters.

Experimental results of the hyperfine structure (hfs) constants of levels of the iodine atom are reported. The absorption spectra of 50 transitions in the near infrared spectral region were observed using concentration modulation technique with a tunable single-mode cw Ti:Sapphire laser. Magnetic dipole hfs constants A and electric quadrupole hfs constants B for 54 levels were determined, out of which for 10 levels were examined for the first time, the constants were confirmed for 44 levels.

We report argon-broadened water vapor transition parameters and their temperature dependence based on measured spectra spanning 6801–7188 cm−1 from a broad-bandwidth, high-resolution dual frequency comb spectrometer. The 25 collected spectra of 2% water vapor in argon ranged from 296 K to 1305 K with total pressure spanning 100 Torr to 600 Torr. A multispectrum fitting routine was used in conjunction with a quadratic speed-dependent Voigt profile to extract broadening and shift parameters, and a power-law temperature-dependence exponent for both. The measurements represent the first broad bandwidth, argon-broadened water vapor absorption study, and are an important step toward a foreign-gas-perturbed, high-temperature database developed using advanced lineshape profiles.

A detailed analysis of the dry air spectrum in the frequency range 180–260 GHz is given. The contributions of monomolecular and bimolecular absorption are discussed. It is shown that the effect of collisional coupling of zero-frequency transitions has a significant impact (up to 60%) on the value of nonresonance absorption. The coefficients of the empirical approximation of the "dry" continuum are redefined. A comparison with the continuum approximation from the Millimeter-wave Propagation Model is given.

The electronic spectra of diethyl carbonate (DEC) based on photoabsorption spectroscopy using synchrotron radiation are investigated in the 6.8-11.5 eV region. The VUV photo absorption spectrum reported here for the first time comprises broad features in the 7-11 eV region with few weak overriding spectral peaks. The broad peaks could be assigned to valence excitations, while the weak ones correspond to the Rydberg series of ns, np, and nd types, thus converging to the first five ionization potentials. Quantum defect values obtained are consistent with the excitation of an electron from oxygen lone pair. Infrared bands of DEC were revisited in the 600-3100 cm−1 region. The observed infrared bands of DEC could be assigned by DFT calculations. The TDDFT methodology is used to compute the vertical excited state energies, valence/Rydberg nature, and oscillator strengths of the excited electronic states. A good agreement using the CAM-B3LYP level of theory is achieved between the theoretically predicted values and experimental observations. In the ionic limit of DEC, the lengthening of the C O and CO–C2H5 bond lengths is predicted. The potential energy curves of the first few excited states assisted in additional insights on the nature of the excited states and their role in photo dissociation dynamics. This study gives a first comprehensive report on the analysis of absorption spectra of DEC in the VUV region and the complete spectral assignments in the VUV and IR regions by quantum chemical calculations.

Gas temperature may be inferred by comparing smoothed measurements of absorption spectra spanning >100 cm−1 to smoothed simulations of the same. Using this thermometry approach in a heated static cell at temperatures up to 1723 K, we studied H2O vapor absorption near 7450 cm−1, dominated by features in the R-branch of the v1 + v3 absorption band. In a first experiment, the cell was operated at 1200–1723 K and 0.0235 bar, while a commercial external cavity diode laser scanned the 7321–7598 cm−1 range. Temperatures inferred from the measured spectra using BT2 simulations were, on average, within 2 K of the actual cell temperature and fell within the limits of error (±0.5% of reading) for the thermocouple used to monitor gas cell temperature. Temperatures inferred using HITEMP2010 simulations were, on average, 38 K lower than actual cell temperatures. In a second experiment, the cell was operated at 296–1723 K and 1 bar while a swept-wavelength laser monitored the 7347–7536 cm−1 range at 10 kHz repetition rate. Temperatures inferred using BT2 simulations were within 3 K of the actual cell temperatures, within the limits of error for the gas cell thermocouple measurements.

We measure speed-dependent Voigt lineshape parameters with temperature-dependence exponents for several hundred spectroscopic features of pure water spanning 6801–7188 cm−1. The parameters are extracted from broad bandwidth, high-resolution dual frequency comb absorption spectra with multispectrum fitting techniques. The data encompass 25 spectra ranging from 296 K to 1305 K and 1 to 17 Torr of pure water vapor. We present the extracted parameters, compare them to published data, and present speed-dependence, self-shift, and self-broadening temperature-dependent parameters for the first time. Lineshape data is extracted using a quadratic speed-dependent Voigt profile and a single self-broadening power law temperature-dependence exponent over the entire temperature range. The results represent an important step toward a new high-temperature database using advanced lineshape profiles.

In the pre-oxygenated ancient Earth atmosphere, the lack of O3 absorption allowed ultraviolet photodissociation of numerous molecules in the troposphere and lower stratosphere. For molecules with narrow line-type absorption spectra, optically thick columns would have produced isotope fractionation due to self-shielding of the most abundant isotopologues. In the lower atmosphere pressure broadening would modify, and in some cases, eliminate these isotope signatures. Shielding is particularly important for quantifying or constraining photolysis-derived isotope effects, such as those believed to explain the sulfur mass-independent fractionation in Archean sedimentary rocks. Here, we report pressure broadening coefficients for natural abundance SO2 in the C ˜ 1 B 2 ← X ˜ 1 A 1 band system at 215 nm. For gas bath pressures up to 750 mbar, we find broadening coefficients of 0.30 ± 0.03 cm−1 atm−1 and 0.40 ± 0.04 cm−1 atm−1 for N2 and CO2, respectively. These broadening coefficients are ∼30% larger than SO2 broadening coefficients previously measured in the B ˜ − X ˜ bands at 308 nm. Because of the highly congested nature of the C ˜ − X ˜ bands, pressure broadening in the early Earth troposphere will cause line profile overlap that will diminish the self-shielding-derived mass-independent isotope fractionation for optically thick SO2 columns. Thus, non-explosive volcanic eruptions may not have left a signature of SO2 self-shielding in the ancient sedimentary rock record.

A broadband absorption spectroscopy diagnostic based on underresolution of the spectral absorption lines is evaluated for the inference of species mole fraction and temperature in combustion systems from spectral fitting. The approach uses spectrally broadband UV light emitting diodes and leverages low resolution, small form factor spectrometers. Through this combination, the method can be used to develop high precision measurement sensors. The challenges of underresolved spectroscopy are explored and addressed using spectral derivative fitting, which is found to generate measurements with high precision and accuracy. The diagnostic is demonstrated with experimental measurements of gas temperature and OH mole fraction in atmospheric air/methane premixed laminar flat flames. Measurements exhibit high precision, good agreement with 1-D flame simulations, and high repeatability. A newly developed model of uncertainty in underresolved spectroscopy is applied to estimate two-dimensional confidence regions for the measurements. The results of the uncertainty analysis indicate that the errors in the outputs of the spectral fitting procedure are correlated. The implications of the correlation between uncertainties for measurement interpretation are discussed.

The very weak absorption spectrum of natural CO2 near 1.74 µm (5702–5879 cm−1) is studied at high sensitivity. The investigated region corresponds to a transparency window of very weak opacity which is of particular interest for Venus. Very weak lines with intensity value as low as 10−30 cm/molecule at 296 K are detected by Cavity Ring Down Spectroscopy. On the basis of the predictions of effective Hamiltonian models, 1135 lines of six carbon dioxide isotopologues - 12C16O2, 13C16O2, 16O12C18O, 16O12C17O, 16O13C18O and 16O13C17O - were rovibrationnally assigned to 26 bands. The accurate spectroscopic parameters of 16 bands are determined from standard band-by-band analysis (typical rms deviations of the line positions are 8 × 10−4 cm−1). These newly observed bands include perturbed bands, weak hot bands and bands of minor isotopologues (in particular 16O12C18O in natural abundance) and provide critical validation tests for the most recent spectroscopic databases. The comparison to the Carbon Dioxide Spectroscopic Databank (CDSD), HITRAN2016 database and recent ab initio line lists is presented. Deficiencies are evidenced for some weak perpendicular bands of the HITRAN2016 list and identified as due to inaccurate CDSD intensities which were preferred to ab initio intensities. While Ames and UCL ab initio intensities are believed to be accurate within a few % for the strong unperturbed bands, the reported measurements allow testing important (>50%) differences between ab initio values of some weak perturbed bands.

The absorption spectra of the mixture of C2H2 and CO2 at different partial pressures of both gases have been recorded at room temperature in the 3 µm region using the Bruker IFS 125 HR FTIR spectrometer. The multispectrum fitting procedure has been applied to these spectra to recover the broadening and shift parameters of the acetylene spectral lines. The CO2 broadening and pressure induced shift coefficients for 119 lines of the ν3 and ν 2 + ( ν 4 + ν 5 ) + 0 bands of acetylene have been derived. The rotational dependence of the values of these coefficients is discussed. The comparison of the obtained coefficients to those published by other authors for the ν1 + ν3 and ( ν 4 + ν 5 ) + 0 bands is performed.

A high-sensitivity absorption spectrum of natural nitrous oxide has been recorded at 10 Torr between 8321 and 8620 cm−1 (1.20 – 1.16 µm). The used cavity ring down spectrometer was referenced to a self-referenced frequency comb providing an accurate frequency scale of the spectra. The predictions of effective operator models were used for the line assignment. All identified bands correspond to the ΔP=14-16 series of transitions, where P= 2V1+V2+4V3 is the polyad number (Vi=1-3 are the vibrational quantum numbers). A total number of 3975 transitions belonging to the 14N216O, 14N15N16O, 15N14N16O,14N218O, and 15N216O isotopologues were measured with estimated accuracy better 1 × 10−3 cm−1 for most of the lines. Compared to the recent analysis of N2O spectra at 1 Torr recorded in the same region (Karlovets et al. JQSRT, 262 (2021) 107508, doi: 10.1016/j.jqsrt.2021.107508), the higher pressure of the recordings and improved quality of the predictions have allowed to: (i) newly assign twenty-two bands, including the 4ν3 band of the 15N216O minor isotopologue, (ii) extend the assignments of previously known bands, (iii) determine the small self-induced pressure shifts of the two strongest bands (less than 10−4 cm−1) by difference of the line positions at 1 and 10 Torr and use them to obtain the zero-pressure value of the line positions, (iv) derive new or improved spectroscopic constants of 69 bands from the standard band-by-band analysis, and (v) analyze six local resonance perturbations affecting three bands, including the identification of a few extra lines due to intensity transfer. Finally, the comparison of the line positions and intensities with their predicted values and with available databases is discussed.

The nature of the water vapour continuum has been of great scientific interest for more than 60 years. Here, water vapour self-continuum absorption spectra are retrieved at temperatures of 398 K and 431 K and at vapour pressures from 1000 to 4155 mbar in the 8800 and 10,600 cm−1 absorption bands using high-resolution FTS measurements. For the observed conditions, the MT_CKD-3.2 model underestimates the observed continuum on average by 1.5–2 times. We use the hypothesis that water dimers contribute to the continuum absorption to simulate the experimentally-retrieved self-continuum absorption spectra, and to explain their characteristic temperature dependence and spectral behaviour. The values of the effective equilibrium constant are derived for the observed temperatures. We find that the dimer-based model fits well to the measured self-continuum from this and previous studies, but requires a higher effective equilibrium constant compared to the modern estimates within the temperature range (268–431 K) and spectral region studied. It is shown that water dimers are likely responsible for up to 50% of the observed continuum within these bands. Possible causes of the incomplete explanation of the continuum are discussed. Extrapolating these measurements to atmospheric temperatures using the dimer-based model, we find that the newly-derived self-continuum reduces calculated surface irradiances by 0.016 W m−2 more than the MT_CKD-3.2 self-continuum in the 8800 cm−1 band for overhead-Sun mid-latitude summer conditions, corresponding to a 12.5% enhancement of the self-continuum radiative effect. The change integrated across the 10,600 cm−1 band is about 1%, but with significant differences spectrally.

Absorption lineshapes for 10 CH4 transitions in the v2 and v4 band were measured at high-resolution in a thermodynamically-controlled optical cell using a quantum cascade laser near 7.16 µm. Linestrength, self-broadening, -narrowing, pressure-shift coefficients and their temperature dependence were recorded over a temperature and pressure range of 290–1050 K and 3–80 kPa, respectively. Voigt, Rautian, speed-dependent Voigt profiles were least-squares fit to the measured absorption spectra to determine the best-fit lineshape parameters. Significant collisional-narrowing and speed-dependent effects were observed but no line mixing behaviour was found in pure CH4 at the experimental conditions. The self-pressure-shift coefficients were found to change signs from negative to positive with increasing temperature and the Frost's formula fit well their temperature dependence for the studied transitions. The measured spectra provided tests of the CH4 line lists near 1397 cm−1 released in HITEMP 2020 and the recorded spectroscopic parameters compared well with the values in the database. Several weak transitions excluded from the HITEMP database were observed at elevated temperatures with the line positions given here. The analyses of uncertainties in all the measured spectroscopic parameters were also demonstrated in this work.

We have measured ammonia line intensities using direct tunable diode laser absorption spectroscopy (dTDLAS) in the 1.5 µm region, and provide new or improved line intensities for 19 absorption lines between 6547 and 6552 cm-1. Our experimental setup was carefully designed to minimize bias and error. Our measured line intensities have at least comparable, or considerably lower uncertainties, and reveal significant differences (up to 40%) compared to literature data. Furthermore, we provide an in-depth quantification and discussion of key sources of uncertainty complying with the guide to the expression of uncertainty in measurement (GUM). Independent NH3 trace amount fraction measurements indicate that our line intensities for the three strongest lines (6548.61, 6548.80 and 6548.92 cm-1) are more accurate than the data listed in the HITRAN database, while our uncertainties are also considerably lower (1, 1 and 3%).

A comprehensive spectroscopic study of the UV–VUV photoabsorption spectrum of nitromethane in the energy region 5.4–11.8 eV (43,500–95,000 cm−1) using synchrotron radiation is presented; the VUV absorption spectrum in the region > 9 eV being reported for the first time. The observed spectral features are assigned to various valence and Rydberg transitions, supported by quantum chemical calculations using the TDDFT method. The 6 eV region is dominated by a broad, intense absorption band peaking at ∼ 6.2 eV assigned to the π-π* valence transition, followed by rich Rydberg series converging to the first four ionization potentials of nitromethane. Theoretical calculations of orbital energies as well as Rydberg series analysis indicate that the third IP is located at 11.95 eV, in contrast to the earlier estimated value of 11.5 eV. Series of bands attributed to vibrational transitions accompanying the 3s (6a″), 3p(6a"), 3s(10a′) and 3s(5a″) Rydberg transitions are observed in the 60,000–73,000 cm−1 region and are tentatively assigned to progressions involving the NO2 in-plane rock and CH3 asymmetric deform modes. The liquid phase IR spectrum is revisited and assigned with the help of DFT calculations. A few new bands are observed and assigned to overtone and combination modes. Theoretically simulated potential energy curves of the first few excited singlet and triplet states with respect to the CN and NO bond lengths are useful in explaining some of the incompletely understood features of the photodissociation dynamics of nitromethane. It is found that direct dissociation in the Franck Condon region is a possible mechanism for the CH3NO + O channel, while singlet-triplet crossings play an important role in CN and NO bond scissions.

Evidence of line mixing has been observed in the infrared spectra of many gaseous species at high densities or in the low absorbing windows between optical transitions. However, up to this point, no study exists of nitric oxide line mixing at pressures above atmosphere or temperatures several hundred degrees above room temperature. In this paper, the absorption spectrum of nitric oxide’s R-branch broadened by N 2 near 5.2 microns is measured with an external cavity quantum cascade laser in a high-pressure, high-temperature optical static cell over a range of temperatures (294 – 802 K) and pressures (5 – 33 atm). An empirically-based, temperature-dependent line mixing model is built by assembling the impact relaxation matrix from fits (energy gap fitting laws) to pressure broadening coefficients that were measured in a previous study. The resulting line mixing model shows significant improvements over a simple superposition of Lorentzian line shapes when compared to the static cell measurements. To further demonstrate the model’s use, the line mixing model is used to infer temperature in high-pressure (10 – 90 atm) shock tube experiments.

A calculated infrared vibration–rotation spectrum of isotopically modified water, H215O, is presented. Oxygen-15 has a half-life of about 2 minutes and H215O may be formed in the atmosphere during thunderstorms as a result of photonuclear processes or when the atmosphere is irradiated by cosmic γ-rays. Variational nuclear motion calculations of vibrational and vibrational-rotational levels up to 25000 cm−1 and up to J = 10 in angular momentum are performed within the framework of the Born-Oppenheimer approximation using an accurate water potential function. The line shape parameters for H215O are estimated. Spectral ranges that are promising for the detection of H215O in the atmosphere are identified and a search for spectral signatures conducted. A spectral feature is tentatively assigned to the 752 (0 1 0) - 643 (0 0 0) line of H215O.

The spectral-line weighted-sum-of-gray-gases (SLW) model is considered as a modern global model, which can be used in predicting the thermal radiation heat transfer within the combustion fields. The past SLW model users have mostly employed the reference approach to calculate the local values of gray gases’ absorption coefficient. This classical reference approach assumes that the absorption spectra of gases at different thermodynamic conditions are scalable with the absorption spectrum of gas at a reference thermodynamic state in the domain. However, this assumption cannot be reasonable in combustion fields, where the gas temperature is very different from the reference temperature. Consequently, the results of SLW model incorporated with the classical reference approach, say the classical SLW method, are highly sensitive to the reference temperature magnitude in non-isothermal combustion fields. To lessen this sensitivity, the current work combines the SLW model with a modified reference approach, which is a particular one among the eight possible reference approach forms reported recently by Solovjov, et al. [DOI: 10.1016/j.jqsrt.2017.01.034, 2017]. The combination is called “modified SLW method”. This work shows that the modified reference approach can provide more accurate total emissivity calculation than the classical reference approach if it is coupled with the SLW method. This would be particularly helpful for more accurate calculation of radiation transfer in highly non-isothermal combustion fields. To approve this, we use both the classical and modified SLW methods and calculate the radiation transfer in such fields. It is shown that the modified SLW method can almost eliminate the sensitivity of achieved results to the chosen reference temperature in treating highly non-isothermal combustion fields.

In order to enhance the solar thermal energy conversion efficiency, we propose to use carbon-gold core-shell nanoparticles dispersed in liquid water. This work demonstrates theoretically that an absorbing carbon (C) core enclosed in a plasmonic gold (Au) nanoshell can enhance the absorption peak while broadening the absorption band; giving rise to a much higher solar absorption than most previously studied core-shell combinations. The exact Mie solution is used to evaluate the absorption efficiency factor of spherical nanoparticles in the wavelength region from 300 nm to 1100 nm as well as the electric field and power dissipation profiles inside the nanoparticles at specified wavelengths (mostly at the localized surface plasmon resonance wavelength). The field enhancement by the localized plasmons at the gold surfaces boosts the absorption of the carbon particle, resulting in a redshift of the absorption peak with increased peak height and bandwidth. In addition to spherical nanoparticles, we use the finite-difference time-domain method to calculate the absorption of cubic core-shell nanoparticles. Even stronger enhancement can be achieved with cubic C-Au core-shell structures due to the localized plasmonic resonances at the sharp edges of the Au shell. The solar absorption efficiency factor can exceed 1.5 in the spherical case and reach 2.3 in the cubic case with a shell thickness of 10 nm. Such broadband absorption enhancement is in great demand for solar thermal applications including steam generation.

Vacuum-ultraviolet (VUV) photoabsorption spectra were recorded of the A 2 Σ + ( v ′ = 0 ) ← X 2 Π ( v ′ ′ = 0 ) , D 2 Σ − ( v ′ = 0 ) ← X 2 Π ( v ′ ′ = 0 ) and D 2 Σ − ( v ′ = 1 ) ← X 2 Π ( v ′ ′ = 0 ) bands of the OH and OD radicals generated in a plasma-discharge source using synchrotron radiation as a background continuum coupled with the VUV Fourier-transform spectrometer on the DESIRS beamline of synchrotron SOLEIL. High-resolution spectra permitted the quantification of transition frequencies, relative f-values, and natural line broadening. The f-values were absolutely calibrated with respect to a previous measurement of A 2 Σ + ( v ′ = 0 ) ← X 2 Π ( v ′ ′ = 0 ) (Wang et al., 1979). Lifetime broadening of the excited D 2 Σ − ( v = 0 ) and D 2 Σ − ( v = 1 ) levels is measured for the first time and compared with previous experimental limits, and implies a lifetime 5 times shorter than a theoretical prediction (van der Loo and Groenenboom, 2005). A local perturbation of the D 2 Σ − ( v = 0 ) level in OH was found.

A high resolution absorption spectrum of neutral fluorine(F I) was observed around 800 nm using concentration modulation absorption spectroscopy with a tunable Ti : Sapphire laser. The fluorine atoms were produced by discharging the mixed gases of helium and sulfur hexafluoride (SF 6 ) in a glass tube. Thirty four hyperfine structure ( hfs ) resolved transitions were analyzed to obtain 23 magnetic dipole hfs constants A for 2 p 4 ( 3 P)3 s , 2 p 4 ( 3 P)3 p and 2 p 4 ( 3 P)3 d configurations. The hfs constants in 2 p 4 ( 3 P)3 s and 2 p 4 ( 3 P)3 p configurations were compared with those obtained from experiments and calculations. Fifteen constants in 2 p 4 ( 3 P)3 d configuration were reported - to our knowledge - for the first time.

Pump modulated laser absorption spectroscopy was used to measure five excited state line shapes for electric dipole allowed transitions beginning in the Rb 5 P manifold. Helium was used as the collisional buffer gas, with pressures from 0 to 250 Torr. Center frequency, FWHM, and asymmetry parameters were extracted from the fits and plotted versus pressure to determine rates. Lines terminating in the 5 D manifold had collisional broadening rates, γ , of 49.5–54.6 MHz/Torr, collisional shift rates, δ of less than ± 1.3 MHz/Torr, and asymmetry rates, β 0 , of less than ± 0.08 mrad/Torr. Lines terminating in the 7 2 S 1 / 2 state showed significantly higher rates, with broadening rates of 109.1–111.0 MHz/Torr, shift rates of 11.5–13.3 MHz/Torr, and asymmetry rates of 0.28–0.47 mrad/Torr. These trends qualitatively match numerically computed difference potentials, which also predict large rates for the 7 S lines and smaller rates for the 5 D lines.

As infrared telescopes are finding evidence of methane in hot exoplanet atmospheres, it is becoming increasingly important to have accurate high-temperature methane absorption models. To evaluate and update several spectroscopic databases (HITRAN2016, HITEMP, ExoMol), we collected laboratory spectra of the methane icosad (6770–7570 cm-1) using a 200 MHz (0.0067 cm-1) dual frequency comb spectrometer. The pure methane data span 18 to 300 Torr and 296 to 1000 K. We found good agreement with the HITRAN2016 model spectrum at room temperature, and substantial mismatch between our spectra and all absorption models at elevated temperature. We present several updates to HITRAN2016 to improve agreement with the measured high-temperature spectra. Specifically, we assign 4283 lower-state energies which had previously been given a default value in HITRAN2016 ( E H I T ″ = 999 cm-1), update existing lower-state energies for 92 features, and add 293 new high-temperature features in order to improve HITRAN2016 above 300 K. Additionally, we update the band-wide line positions by ∼ 0.001 cm-1, the self-widths by +7%, and we estimate band-averaged temperature-dependence exponents for self-width (0.85) and self-shift (0.58). These measurements are an important step towards merging empirical and theoretical high-temperature methane databases, with the goal of enabling better understanding of exoplanet atmospheres.

A detailed spectroscopic study on ethyl methyl carbonate, a green solvent, has been carried out by recording vacuum ultraviolet and infrared spectra. The vacuum ultraviolet photoabsorption spectrum is recorded using synchrotron radiation from Photophysics beamline at the Indus-1 synchrotron radiation source at RRCAT, Indore, India in the wavelength region of 7–11.5 eV. Infrared spectra in gas phase as well as matrix isolated case are recorded using an indigenously developed laboratory low temperature experimental facility and a Fourier transform infrared spectrometer in the 500–4000 cm−1 region. Geometry optimization, vibrational frequency analysis of neutral & ionized ethyl methyl carbonate and electronic excited state energy information has been obtained using quantum chemical calculations. The observed ir spectral features could be assigned to the fundamental vibrational modes of the molecule. The vacuum ultraviolet region comprising a broad continuum is assigned to valence transitions having high oscillator strengths and overlying weak bands to ns, np, nd type Rydberg transitions. Potential energy curves of the ground and first few low lying excited states generated provided additional insights into their nature and further interpretation of observed experimental spectra. In this paper we report the first electronic absorption spectrum in 7 to 11.5 eV region, its spectroscopic analysis and identification of vibrational modes in the infrared spectra for ethyl methyl carbonate. Results of quantum chemical simulations carried out to obtain nature of excited states, energies and vibrational frequencies using GAMESS (USA) quantum chemistry code are also reported in this paper.

Wavelength modulation-direct absorption spectroscopy (WM-DAS) has been used to measure the absorption line shapes of the H 2 O transition at 7299.431 cm − 1 and the CO transition at 4297.705 cm − 1 perturbed by Ar, N 2 and He. The foreign-gas broadening, narrowing and pressure-shift parameters were determined from various lineshape models at pressures from 1 to 100 kPa. The measured N 2 -broadening coefficients are the largest among the three perturbers and the measured N 2 - and Ar-pressure-shift coefficients are both negative while that for He is positive. The nonlinear pressure dependence of the velocity-changing rates for the Galatry and Rautian profiles and the speed-dependent coefficients for Speed-dependent Voigt profile were all observed for the 6 binary systems. The measured velocity-changing rates were all larger than the corresponding dynamic friction coefficients in H 2 O -Ar/ N 2 /He while smaller than those in CO-Ar/ N 2 /He. The narrowing parameters were also retrieved and compared by taking both the Dicke narrowing and speed dependent effects into account. The partially Correlated quadratic Speed-dependent Hard-Collision profile was simulated and fit by the other simplified profiles to further validate the nonlinear behaviour of the narrowing parameters, which is consistent with the measured results.

We report measurements and analysis of the vibrational-rotational absorption spectrum of the Н217О molecule in the visible range from 17000 to 20000 cm−1. Measurements were carried out using an IFS-125M Fourier spectrometer with a resolution of 0.1 cm−1, at a pressure of 24 mbar, a temperature of 25°С, and an optical path length of 24 m. A CREE XPE GRN LED, having its maximal radiation intensity in the region of 520 nm, was used as a source of radiation. The spectra were identified using calculations of the EXOMOL group [Polyansky et al Mon Not R Astron Soc 2017;466:1363–1371]. The least squares fitting method was used to determine the parameters of the Voigt profile: the line centers, intensities, and half-widths. The spectrum analysis produced a line list that contained 159 lines of the Н217О molecule in the studied region and a set of 107 experimental energy lines. We compare the obtained experimental data on the absorption of the Н217О molecule with the calculated data of other authors.

The absorption spectra of carbon dioxide have been recorded in the near infrared region from 10,000 to 10,300 cm -1 , 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 a spectral resolution of 0.03 cm − 1 , room temperature, a path length of 953.6 m and at two pressures of 294 and 523 mbar. The achieved sensitivity (noise equivalent absorption) at the level of k ν =1.38×10 − 10 cm −1 allowed detection of a number of new transitions with the intensity values down to 10 –29 cm/molecule at 296 K. Two bands 60014-00001 and 60015-00001 of 12 C 16 O 2 were detected for the first time. The line positions and intensities of these bands were determined using the Voigt profile as a line shape. The uncertainty of the line position determination was estimated to be about 0.003 cm -1 for the unblended lines with a high value of the signal-to-noise ratio. The uncertainty of the line intensity determination varies from 4% to 40% depending on the strength of the line and the extent of the line overlapping. The measured line intensities of the 60014-00001 and 60015-00001 bands together with those published earlier for the Δ P =15 series of transitions were used to fit the effective dipole moment parameters of this series. Here P =2 V 1 + V 2 +3 V 3 is the polyad number ( V i ( i =1,2,3) are the harmonic oscillators quantum numbers). The fitted parameters reproduce the measured line intensities within their experimental uncertainties. Using the effective Hamiltonian parameters published earlier and the fitted effective dipole moment parameters the line positions and intensities of the 6001 i -00001 ( i =1,2,3,4,5,6,7) bands have been calculated. A comparison of the measured line positions and intensities to those contained in the new version ( huang.seti.org ) AMES line list as well as in the High-T line list are given.

A study of the vibration-rotation absorption spectrum of the D2O molecule in the range 10100–10800 cm-1 has been performed. The spectrum was recorded using a Fourier Transform Spectrometer with the spectral resolution of 0.05 cm-1 coupled to the multi-pass White-type cell providing an optical path length of 24 m. A light-emitting diode was used as the radiation source, giving a high brightness that resulted in an S/N ratio of measurements of about 104. The rovibrational assignment of more than 920 lines was carried out, and the parameters of the spectral lines (i.e. centers, intensity and half-width) were determined by least-squares fitting of the Voigt contour parameters to the experimental data. A total of 530 rotational energy levels belonging to nine vibrational states (301), (103), (400), (221), (122), (320), (004), (023) and (042) and with maximum rotational quantum numbers J=16 and Ka=9 was determined. 101 energy levels were derived from the experiment for the first time.

Lorentz half-width coefficients and their temperature dependence exponents for CO2 broadening in the fundamental bands of HDO are important for reliable and accurate interpretation of Mars and Venus atmospheric data and to determine D/H. Uncertainties in the temperature dependences of the CO2-broadened half-width coefficients lead to large errors in the retrieved mixing ratios and hence in HDO column abundances. In this high-resolution FTIR laboratory study, we report first measurements of the temperature dependences of half-width coefficients for HDO transitions in the ν1 and 2ν2 bands broadened by CO2. Accurate line positions, intensities, CO2-broadened width and pressure shift coefficients, their temperature dependences, collisional line mixing coefficients for HDO-CO2 system and quadratic speed dependence parameters have been retrieved for a large number of transitions in the ν1 band. Room-temperature self-broadened half-width coefficients, self-shift coefficients, and collisional line-mixing coefficients for HDO-HDO system were also measured for the same number of ν1 transitions. Positions and intensities were measured for nearly 60 transitions in the weaker 2ν2 band along with a few room-temperature measurements of CO2- and self-broadening and pressure-shift coefficients. These results were obtained from simultaneous nonlinear least squares fittings of ten high-resolution absorption spectra recorded with the Bruker IFS-125HR FTS at JPL and two coolable sample cells. Modified Complex Robert-Bonamy (MCRB) formalism was applied to compute both types of broadening and pressure shift coefficients, and the temperature dependences of the CO2- and self-broadening parameters. Present measurements are compared with the MCRB calculations and other theoretical values reported in the literature.

Absorption cross-sections of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) were derived from Fourier transform infrared spectra recorded from 530 to 3400 cm − 1 with a resolution of 0.1 cm − 1 over a temperature range of 300–362 K. These results were compared to previously published experimental measurements made at room temperature and to a theoretical spectrum from density functional theory (DFT) calculations. Good agreement is found between the experimentally derived results, DFT calculations, and previously published data. The only temperature dependence observed was in the amplitude of some of the absorption peaks due to the changing ratio of the stable conformations of HFIP. This temperature dependence does not result in a significant trend in integrated band strength as a function of temperature. The average value for integrated band strength is found to be (2.649 ± 0.065)x10 − 16 cm molecule − 1 for HFIP over the spectral range of 595 to 3010 cm − 1 . Radiative efficiency (RE) and the global warming potential (GWP) for HFIP were also derived. A RE of 0.293 ± 0.059 Wm − 2 ppbv − 1 is derived, which leads to a GWP100 of 188 in the range of 530 to 3000 cm − 1 . The DFT calculation is linearly adjusted to match the experimental spectrum. Using this adjusted DFT spectrum to expand the range below 530 to 0 cm − 1 , increases the RE to 0.317 ± 0.063 Wm − 2 ppbv − 1 and the GWP100 to 203.