Infrared Absorption Cross Sections Research Articles

Synchrotron Near-Field Infrared Nanospectroscopy and Nanoimaging of Lithium Fluoride in Solid Electrolyte Interphases in Li-Ion Battery Anodes.

Lithium fluoride (LiF) is a ubiquitous component in the solid electrolyte interphase (SEI) layer in Li-ion batteries. However, its nanoscale structure, morphology, and topology, important factors for understanding LiF and SEI film functionality, including electrode passivity, are often unknown due to limitations in spatial resolution of common characterization techniques. Ultrabroadband near-field synchrotron infrared nanospectroscopy (SINS) enables such detection and mapping of LiF in SEI layers in the far-infrared region down to ca. 322 cm-1 with a nanoscale spatial resolution of ca. 20 nm. The surface sensitivity of SINS and the large infrared absorption cross section of LiF, which can support local surface phonons under certain circumstances, enabled characterization of model LiF samples of varying structure, thickness, surface roughness, and degree of crystallinity, as confirmed by atomic force microscopy, attenuated total reflectance FTIR, SINS, X-ray photoelectron spectroscopy, high-angle annular dark-field, and scanning transmission electron microscopy. Enabled by this approach, LiF within SEI films formed on Cu, Si, and metallic glass Si40Al50Fe10 electrodes was detected and characterized. The nanoscale morphologies and topologies of LiF in these SEI layers were evaluated to gain insights into LiF nucleation, growth, and the resulting nuances in the electrode surface passivity.

Measurements of infrared absorption cross-sections for n-C3F8, c-C4F8, n-C4F10, and n-C5F12 from 298 to 350 K

Perfluoro-n-propane, perfluorocyclobutane, perfluoro-n-butane, and perfluoro-n-pentane are non-ozone-depleting industrial alternatives to chlorofluorocarbons and hydrochlorofluorocarbons. However, these perfluoroalkanes have significant band strength in the atmospheric window from 800 to 1200 cm−1. Coupled with their millennial-scale atmospheric lifetimes, they can lead to significant long-term global warming. Infrared spectra are required to quantify the climate impacts. This work provides a set of high-temperature infrared absorption cross-sections in the range 298–350 K at 0.1 cm−1 resolution from 515 to 1500 cm−1 for each compound. Our cross-sections generally agree with literature measurements except for perfluoro-n-pentane. We use density functional theory to calculate the absorption cross-sections from 0 to 515 cm−1 using the B3LYP functional and several basis sets. The 6-31G(d,p) basis set provides the best results for linear perfluoroalkanes, while the def2-TZVP basis set provides the best results for cyclic perfluoroalkanes. Using experimental cross-sections, we calculate the radiative efficiency and global warming potential for each compound, utilizing the Pinnock curve from Shine and Myhre (2020) and atmospheric lifetimes from Hodnebrog et al. (2020). These quantities are found to be independent of temperature. The average 100-year global warming potential derived from all cross-sections is 9,610±1,260, 10,800±1,420, 10,100±1,330, and 9,380±1,230 for perfluoro-n-propane, perfluorocyclobutane, perfluoro-n-butane, and perfluoro-n-pentane, respectively. Combining the data in this work with our previous measurements reveals that the global warming potential for perfluoroalkanes with an increasing number of CF bonds depends on the ratio of radiative efficiency to molecular weight.

Measurements of perfluoro-n-hexane and perfluoro-2-methylpentane infrared absorption cross-sections from 298 to 350 K

Perfluoro-n-hexane and perfluoro-2-methylpentane are fully fluorinated alkanes used as non-ozone-depleting alternatives to chlorofluorocarbons and hydrochlorofluorocarbons. These compounds are long-lived and potent greenhouse gases due to their strong CF bonds and infrared absorption in the atmospheric window. Infrared absorption cross-sections are required to quantify the climate impact of these compounds via the radiative efficiency and global warming potential. To our knowledge, there are only two experimental measurements for perfluoro-n-hexane, and there are no experimental measurements for perfluoro-2-methylpentane in the infrared. In this work, we provide a set of absorption cross-sections in the range 515–1500 cm−1, at 0.1 cm−1 resolution from 298 to 350 K for each compound. We calculate the absorption cross-section between 0 and 515 cm−1 using density functional theory with various basis sets. The 6-31,G(d,p) basis set with the B3LYP functional is found to provide the best results. Using both measurements and calculations combined, we calculate the radiative efficiency and global warming potential for each compound. No significant temperature dependence was observed in these quantities. The average radiative efficiency derived from all cross-sections is 0.48 ± 0.06 W m−2 ppbv−1 for perfluoro-n-hexane and 0.46 ± 0.06 W m−2 ppbv−1 for perfluoro-2-methylpentane. The average 100-year global warming potential derived from all cross-sections is 9590 ± 1260 for perfluoro-n-hexane and 9220 ± 1210 for perfluoro-2-methylpentane.

Research Progress in Surface-Enhanced Infrared Absorption Spectroscopy: From Performance Optimization, Sensing Applications, to System Integration.

Infrared absorption spectroscopy is an effective tool for the detection and identification of molecules. However, its application is limited by the low infrared absorption cross-section of the molecule, resulting in low sensitivity and a poor signal-to-noise ratio. Surface-Enhanced Infrared Absorption (SEIRA) spectroscopy is a breakthrough technique that exploits the field-enhancing properties of periodic nanostructures to amplify the vibrational signals of trace molecules. The fascinating properties of SEIRA technology have aroused great interest, driving diverse sensing applications. In this review, we first discuss three ways for SEIRA performance optimization, including material selection, sensitivity enhancement, and bandwidth improvement. Subsequently, we discuss the potential applications of SEIRA technology in fields such as biomedicine and environmental monitoring. In recent years, we have ushered in a new era characterized by the Internet of Things, sensor networks, and wearable devices. These new demands spurred the pursuit of miniaturized and consolidated infrared spectroscopy systems and chips. In addition, the rise of machine learning has injected new vitality into SEIRA, bringing smart device design and data analysis to the foreground. The final section of this review explores the anticipated trajectory that SEIRA technology might take, highlighting future trends and possibilities.

Infrared absorption cross sections for propene broadened by N2 (450–1250 cm−1) and by H2 (2680–3220 cm−1)

Propene (C3H6) has been measured in the planetary atmospheres of Earth and Titan, and may be detected in the giant planets by infrared spectroscopy. Propene infrared absorption cross sections have been determined in the 2680–3220 cm−1 and 450–1250 cm−1 regions by high-resolution Fourier transform spectroscopy with H2 and N2, respectively, as broadening gases. Samples of propene were held at 202, 232, 265, 297 K.

Infrared absorption cross section and radiative forcing efficiency features of four hydrofluoropolyethers: Performance of some DFT functionals

The present work aimed to investigate the infrared absorption cross section spectra using a series of eight DFT methods including DSD-PBEP86, B2PLYP, B3LYP, BLYP, G96LYP, M06-L, PBEPBE, and TPSSTPSS with basis sets Def2-TZV and Def2-TZVP. These were assigned to a series of four H-Galdens noted HG-00, HG-10, HG-01, and HG-11. The experimental infrared spectra of these gases provided by Myhre et al. [Atmos. Environ. 33 (1999) 4447] are well reproduced using the method M06-L/Def2-TZVP over the frequency range 0–3200 cm−1. The radiative forcing efficiency, descriptor of climate effect, was estimated using the narrow band model and corrected with a lifetime factor for different computational methods. The double hybrid functionals yield accurate results compared to experiment in the range 0–2500 cm−1 for HG-00, HG-10, and HG-01, and in the range 600–1600 cm−1 for HG-11. The other functionals are in good agreement over the specific frequency ranges.

Absorption cross sections of n-butane, n-pentane, cyclopentane and cyclohexane

The infrared absorption cross sections of pure n-butane, n-pentane, cyclopentane and cyclohexane have been measured in the 3.3 µm region (and 6.8 µm region for cyclopentane) by high resolution Fourier transform spectroscopy. The samples had temperatures of 294 K and 230 K for n-butane, 294 K and 218 K for n-pentane, 296 K and 235 K for cyclopentane, and 294 K and 222 K for cyclohexane. These spectra are important for molecular identification in extraterrestrial environments such as Saturn's moon Titan, giant planets and exoplanets. All spectra are provided as data point files.

Determination of the infrared absorption cross-section of the stretching vibrations of Ge–O bonds in GeOx films

The cross-section of the infrared (IR) absorption of the Ge-O stretching mode in both GeO2 and GeOx films was determined. The GeO2 film was obtained by thermal oxidation of germanium while the GeOx film was obtained by physical vapor deposition. The latter was then annealed at a temperature of 550 °C for 30 min. Both the as-deposited and the annealed films were studied using IR absorption spectroscopy, Raman spectroscopy, ellipsometry and X-ray photoelectron spectroscopy. We found the absorption cross-section is about 2 ÷ 2.6·10–19 cm−2 for the GeO2 films and 0.8·10−19 cm−2 for the GeOx (x ∼ 1.1) film.

Infrared absorption cross sections, and oscillator strengths of interstitial and substitutional double donors in silicon

Infrared absorption cross sections and corresponding oscillator strengths of several intracenter transitions of double donors in silicon, interstitial magnesium (Mg; group IIA) and substitutional chalcogens (Ch = S; Se; group VI), were determined for impurity densities in the ranges $1\ifmmode\times\else\texttimes\fi{}{10}^{14}--1.6\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.16em}{0ex}}\mathrm{atoms}/\mathrm{c}{\mathrm{m}}^{3}$ for Mg and $2\ifmmode\times\else\texttimes\fi{}{10}^{13}--2\ifmmode\times\else\texttimes\fi{}{10}^{16}\phantom{\rule{0.16em}{0ex}}\mathrm{atoms}/\mathrm{c}{\mathrm{m}}^{3}$ for chalcogens. The concentrations of electrically active atomic and diatomic donor centers were derived from the Hall effect measurements. The experimental integrated cross sections were obtained from low-temperature impurity absorption spectra. The oscillator strengths of related donor transitions were derived and compared with those for shallow single donors in silicon, both determined experimentally and predicted theoretically. The transitions of oscillator strengths of double donors follow the decreasing trend with decreasing radius of donor ground states and increasing an impurity binding energy.

Reshaping plasmonic resonances using epsilon-near-zero materials for enhanced infrared vibrational spectroscopy

Surface-enhanced infrared absorption (SEIRA) spectroscopy is a powerful technique for a label-free identification of molecular species. The low infrared absorption cross sections of molecules are made up for the huge electromagnetic field enhancement provided by the resonant excitation of collective electron oscillations in metallic nanoantennas. Since these surface plasmons are localized at the nanometer scale, a minute amount of materials is detected leading to a weak SEIRA signal. The design of actual plasmonics detectors is a trade-off between the detection of very small volumes of molecules and the signal to noise ratio level. We demonstrate that an epsilon-near-zero (ENZ) material combined with nano-slits lifts this constraint and provides both extreme enhancement factor up to 107 and highly contrasted SEIRA signal for an extremely low amount of material of interest. These results are explained by the modification of the electromagnetic field of the gap plasmon mode sustained by the slits in the presence of the ENZ material. We propose to implement this concept with a semiconductor whose doping level engineering provides a versatile way to scan the whole molecules' fingerprint frequency range.

The HITRAN2020 molecular spectroscopic database

The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years).All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules.The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition.

Gas-phase IR cross-sections and single crystal structures data for atmospheric relevant nitrocatechols

The gas-phase IR absorption cross sections for 3-nitrocatechol, 5-methyl-3-nitrocatechol, 4-nitrocatechol and 4-methyl-5-nitrocatechol were evaluated using the ESC-Q-UAIC (the environmental simulation chamber made of quartz from the “Alexandru Ioan Cuza” University of Iasi, Romania) photoreactor facilities. Specific infrared absorptions and integrated band intensities in the range of 650–4000 cm−1 were investigated by long path gas-phase FT-IR technique. Two different addition methods (solid and liquid transfer methods) of nitrocatechols into the reactor were employed in these investigations. All investigated nitrocatechols were synthesized and characterized by X-ray diffraction spectroscopy techniques beside traditional nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy in order to evaluate their structure-properties relationship in gas and solid phase. This study reports for the first time the gas-phase infrared cross sections and the X-ray diffraction analysis for (methyl) nitrocatechols.

Comment on erratum to “Infrared absorption cross sections of isobutane with hydrogen and nitrogen as broadening gases J Quant Spectrosc Radiat Transf 227 (2019) 226-229”, J Quant Spectrosc Radiat Transf 242 (2020) 106771

• PNNL infrared absorption cross sections for isobutane are correct. • A recent erratum casting doubt on the PNNL data is incorrect. • Corrected isobutane cross sections are provided.

Absorption cross sections in the CH stretching region for propene broadened by helium and nitrogen

Propene infrared absorption cross-sections are important for quantitative analysis of atmospheric spectra. Propene has been observed in Titan's atmosphere and may be detected in the atmospheres of giant planets. Infrared absorption cross-sections of propene (C3H6) have been measured in the 2680–3220 cm−1 region by high-resolution Fourier transform spectroscopy. Samples of propene were held at 202, 232, 265, 295 K with helium and nitrogen broadening gas pressures of 10, 30, 100 Torr. The cross section files are available for download.

New infrared absorption cross sections of difluoromethane (HFC-32) for atmospheric remote sensing

Difluoromethane (CH2F2; HFC-32), a hydrofluorocarbon (HFC) used as a refrigerant in air conditioning and heat pump systems, is currently being phased out under the terms of the Montreal Protocol (Kigali Amendment). In order to monitor its concentration profiles using infrared-sounding instruments, for example the Atmospheric Chemistry Experiment – Fourier transform spectrometer (ACE-FTS), accurate laboratory spectroscopic data are required. This work describes new high-resolution infrared absorption cross sections of difluoromethane / dry synthetic air over the spectral range 850–1335 cm−1, derived from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26-cm-pathlength cell. Spectra were recorded at resolutions between 0.009 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD = maximum optical path difference) over a range of temperatures and pressures (7.6–760 Torr and 188–297 K). The new absorption cross sections in this work improve upon those currently available in HITRAN for remote sensing.

Infrared absorption cross sections for hot isobutane in the CH stretching region

Spectra of pure isobutane were recorded at high temperature in the C-H stretching region (2750-3050 cm−1) with a high resolution Fourier transform spectrometer. Isobutane absorption cross sections were determined for six temperatures from 295 K to 739 K. These data may be useful for simulations of hot Jupiter exoplanets and brown dwarfs. Integrated cross sections were compared with adjusted cross section data from the Pacific Northwest National Laboratory (PNNL) database.

New infrared absorption cross sections for the infrared limb sounding of carbon tetrafluoride (CF4)

Carbon tetrafluoride (CF4), also known as tetrafluoromethane and sometimes CFC-14, has a natural lithospheric source, however the enhanced modern-day concentrations relative to this natural source have arisen from leaks into the atmosphere by industry, most significantly related to the production of aluminium and semiconductors. A potent greenhouse gas, with one of the longest atmospheric lifetimes of 50,000 years, the abundance of carbon tetrafluoride is steadily increasing in the atmosphere. In order to monitor its concentration profiles using infrared sounders, accurate laboratory spectroscopic data are required. This work describes new high-resolution infrared absorption cross sections of pure and air-broadened carbon tetrafluoride over the spectral range 1190–1336 cm−1, derived from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26-cm-pathlength cell. Spectra were recorded at resolutions between 0.0018 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD = maximum optical path difference) over a range of atmospherically relevant temperatures (190 – 296 K) and pressures (up to 760 Torr). These new absorption cross sections improve upon those previously used for remote sensing, and will provide a more accurate basis for retrievals in the future.

New infrared absorption cross sections for the infrared limb sounding of sulfur hexafluoride (SF6)

Sulfur hexafluoride (SF6), widely used in industry for electrical insulation, is a potent greenhouse gas with a steadily increasing atmospheric abundance. In order to monitor its concentration profiles using infrared sounders, accurate laboratory spectroscopic data are required. This work describes new high-resolution infrared absorption cross sections of pure and air-broadened sulfur hexafluoride over the spectral range 780 – 1100 cm−1, derived from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26-cm-pathlength cell. Spectra were recorded at resolutions between 0.002 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD = maximum optical path difference) over a range of atmospherically relevant temperatures (189 – 294 K) and pressures (up to 751 Torr). These new absorption cross sections improve upon those previously used for remote sensing, and will provide a more accurate basis for retrievals in the future.

Radiative efficiency and global warming potential of the hydrofluoroether HFE-356mec3 (CH3OCF2CHFCF3) from experimental and theoretical infrared absorption cross-sections

Experimental absorption cross-section spectra of HFE-356mec3 (CH3OCF2CHFCF3) have been acquired at three temperatures and at a resolution of 0.1 cm−1 over the spectral range 550–3500 cm−1. The results have been completed with theoretical calculations using density functional theory and ab initio methods at different levels of theory. A lifetime-corrected radiative efficiency of 0.31 Wm−2ppb−1 was obtained, leading to a 100-year time horizon global warming potential of 260 using an atmospheric lifetime of 2.5 years.

High-resolution cavity ring-down spectroscopy of the ν1 + ν6 combination band of methanol at 2.0 μm.

Reported here are portions of the infrared absorption cross section for methanol (CH3OH), as measured by frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) at wavelengths near λ = 2.0 µm. High-resolution spectra of two gravimetric mixtures of CH3OH-in-air with nominal mole fractions of 202.2 µmol/mol and 45.89 µmol/mol, respectively, were recorded at pressures between 0.8 kPa and 102 kPa and at a temperature of 298 K. Covering the experimental wavenumber range of 4990 cm-1 to 5010 cm-1 in increments of 0.0067 cm-1 and with an instrument linewidth of 30 kHz, we observed an evolution in the CH3OH spectrum from resolved absorption lines at a low pressure (0.833 kPa) to a pseudocontinuum of absorption at a near-atmospheric pressure (101.575 kPa). An analysis of resolvable features at the lowest recorded pressure yielded a minimum intramolecular vibrational energy redistribution (IVR) lifetime for the OH-stretch (ν1) plus OH-bend (ν6) combination of τIVR ≥ 232 ps-long compared to other methanol overtones and combinations. Consequently, we show that high-resolution FS-CRDS of this relatively weak CH3OH combination band provided an additional avenue by which to study the intramolecular dynamics of this simplest organic molecule with hindered internal rotation.