Ν3 Band Research Articles

Depolarization Ratio of the ν1 Raman Band of Pure CH4 and Perturbed by N2 and CO2.

In this work, the effect of nitrogen and carbon dioxide on the depolarization ratio of the ν1 band of methane in the pressure range of 0.1–5 MPa is studied. A high-sensitivity single-pass Raman spectrometer was used to obtain accurate results. Moreover, we took into account the overlap of the ν1 band by the ν3 and ν2 + ν4 bands using the simulation of their spectra. The depolarization ratio of the ν1 band in pure methane is within 0–0.001, and the effect of nitrogen and carbon dioxide on this parameter is negligible in the indicated pressure range. The obtained results are useful for correct simulation of the Raman spectrum of methane at different pressures, which is necessary to improve the accuracy of gas analysis methods using Raman spectroscopy.

Multi-spectral investigation of ozone: Part II. Line intensity measurements at one percent accuracy around 5 µm and 10 µm

Ozone line parameters have been retrieved from high-resolution Fourier transform spectra in the 5-µm and 10-µm spectral regions using a H-shaped cell with two parallel paths described in the first paper of the series (Multi-spectral investigation of ozone: Part I. Setup & uncertainty budget). The experimental arrangement allows for quasi simultaneous acquisition of spectra at 5 µm and 10 µm with consistent ozone pressure. A multispectrum fitting procedure has been used to accurately measure line positions and intensities. Special care has been taken to determine the instrument line shape and its effect on line intensities and sources of uncertainties from the assumption of a molecular line profile have been investigated.Line positions and intensities have been retrieved for 497 transitions at 10 µm, mostly (476) from the ν3 band, but also from the ν1 band (18 transitions) and from the ν2+ν3–ν2 hot band (3 transitions). At 5 µm, 319 transitions have been determined, of which 316 belong to the ν1+ν3 and 3 to the 2ν3 bands. Comparisons with previous experiments and calculations as well as with databases are presented, showing systematic discrepancies. The new intensity data at the unprecedented 1% accuracy level unambiguously indicates that atmospheric databases currently suffer from systematic biases up to 4.2% in the ν1+ν3 band and 2.2% in the ν3 band. The present results will help to resolve the long-standing UV-IR discrepancy observed in atmospheric and laboratory ozone studies. Comparisons with yet unpublished measurements and Hamiltonian-type calculations, as well as with recently published ab-initio calculations show an average discrepancy between 0.1% and 1.2% with sub-percent (0.4–0.8%) dispersion. The small scatter of the comparison confirms the sub-percent precision of both, the calculations, and the measurements.

New line positions and effective line intensities of the ν2 band cis-HONO near 1661 cm−1 from quantum cascade laser absorption spectroscopy

High-resolution quantum cascade laser absorption spectrum of cis-HONO of the v2 band has been recorded and analyzed, for the first time, in the mid-infrared region of 1659.2–1662.2 cm−1 (R-branch of the v2 band, N=O stretch). Positions and effective line intensities were determined for about 60 new lines. The absolute absorption frequencies were directly measured during spectral scan using a wavelength meter with an accuracy of ∼0.0017 cm−1. The corresponding simulation spectrum was calculated using the PGOPHER code. The calculated line positions are in a good agreement with the experimentally measured frequencies within the wavelength meter uncertainty. Effective line intensities were determined, with uncertainties of about 17%, by scaling the measured HONO absorption intensities to the previously reported line intensity of a cis-HONO line located in the same spectral region near 1659.85 cm−1.

Line intensity parameters, He-broadening and line shift coefficients in the 2v 2 0 and 3v 2 1 − v 2 1 bands of OCS

Using Fourier transform spectrometer, He-broadening coefficients in the and bands of carbonyl sulfide (16O12C32S) have been measured for the first time in the P- and R-branches. Measurements have been performed at room temperature (295 K) for 200 ro-vibrational lines with rotational quantum number ranging from 1 ≤ J ≤ 64, using a mono-spectrum non-linear least squares fitting of Voigt profiles. The measured values were discussed as a function of the rotational quantum number and compared to previous data. These broadening coefficients were also calculated on the basis of Robert and Bonamy's formalism using an ab-initio potential energy surface (PES). In addition, we have measured pressure shift coefficients for 92 transitions in both bands, these results were compared with those of the 2ν3 band. The line intensities in the and bands were also retrieved using the same spectra. The analysis of these intensities allows us to derive a consistent set of line intensity parameters such as vibrational transition moments, band intensities as well as Herman-Wallis (HW) coefficients.

Cavity-ring-down spectroscopy of the heavy ozone isotopologue 18O3: Analysis of a high energy band near 95% of the dissociation threshold

The absorption spectrum of the 18O3 isotopologue of ozone was recorded by cavity-ring-down spectroscopy between 7920 and 7985 cm−1 with a routine noise equivalent absorption, αmin, on the order of a few 10−11 cm−1. This permitted to detect and analyze an extremely weak vibrational band assigned as 7ν1+ν3 following predictions from the ab initio potential energy surface reported in J Chem Phys 2013;139:134307. This is the most excited rovibrational band of the 18O3 isotopologue detected so far. In total, 259 ro-vibrational transitions were measured and modeled using an effective Hamiltonian model. The vibrational dipole transition moment parameter of the band deduced from the analysis and the fit to 177 experimental line intensities was evaluated as 2.6 × 10−6 Debye. The absorption coefficient of the recorded pure 18O3 spectrum was found significantly smaller compared to that of the 16O3 in the same range. The set of 171 upper state energies experimentally determined cover the range from 92.6% (at J = 1) to 97% (at J = 26) of the first dissociation threshold D0. The comparison with ab initio predictions for the band origin and ʋ-dependent rotational constants is discussed. An absorption line list containing 477 transitions is provided as Supplementary material for the 7ν1+ν3 band.

N2O–Ar and N2O–Kr: Intermolecular vibrations of N2O–Kr and symmetry breaking of the N2O bending mode in the presence of a rare gas

Rotationally-resolved infrared spectra of N2O–Ar and N2O–Kr are studied in the region of the N2O ν1 vibration (≈2224 cm−1) using a tunable Quantum Cascade laser source to probe a pulsed supersonic jet. The N2O–Kr ν1 fundamental band is re-analyzed, together with previous ν3 band data, using a unified scheme to fit the (small) observed Kr isotope splittings. This scheme is then transferred to analyze the bending combination band of N2O–Kr near 2257 cm−1 where isotope effects are much larger due to stretch-bend interactions. As a result, N2O–Kr intermolecular bend (33.29 cm−1) and stretch (34.48 cm−1) frequencies are directly determined for the first time. Weak spectra are detected for both N2O–Ar and –Kr corresponding to the (ν1, ν2l2, ν3) = (1110) ← (0110) hot band of N2O. Their analysis yields the magnitude of the splitting of the N2O ν2 bending mode into in-plane and out-of-plane components. These splittings are found to be significantly smaller than those observed in the analogous CO2-containing dimers.

High-Resolution spectroscopy and analysis of the fundamental modes of [formula omitted]Si[formula omitted]. Accurate experimental determination of the Si[formula omitted]F bond length

Silicon tetrafluoride (SiF4) is a trace component of volcanic gases and is gaining industrial importance. However, a better knowledge of spectroscopic parameters is needed for this molecule in order to derive accurate concentrations. Following a previous reinvestigation of the ν3 and ν4 fundamentals (Richard et al. 2021), we have undertaken an extensive high-resolution study of its infrared absorption bands. We present here an update of this study. It features the recording of new far-infrared spectra, taking advantage of synchrotron radiation, and a global fit giving a consistent parameter set for the ground and fundamental states of 28SiF4, now including the v1=1 and v2=1 states, by adding to the global analysis the newly measured ν2, ν1−ν4, and ν4−ν2 bands near 264, 412, and 125 cm−1, respectively. Nearly 20000 assigned lines pertaining to seven distinct rovibrational bands were fitted with an excellent accuracy (global standard deviation of 0.296). This allows us to obtain an accurate experimental value for the Si−F bond length, re(SiF4)=1.5516985(30) Å. Some new band intensity estimates allow us to update our SiF4 calculated spectroscopic database.

The 5.8 µm absorption bands for nitric acid (H14N16O3): line positions and intensities for the ν2 band at 1709.567 cm−1 and for its first associated hot bands (ν2+ν9−ν9, ν2+ν7−ν7, ν2+ν6−ν6)

This paper is the second of two back-to-back works, whose goal was to generate a more accurate linelist for the 5.8 µm absorption band of HNO3. Here, we report improved line positions and intensities in the ν2 cold band which is the main band in this region. For this, we recorded four high-resolution Fourier transform spectra for the ν2 band, centered at 1709.567 cm−1, under different experimental conditions. Using these spectra, a new extended line position analysis was performed for the ν2 band, leading to more accurate line positions. In parallel, individual line intensities were measured. It appears that, although the ν2 band is mainly of B-type, it also possesses a (very) weak A-type component that cannot be ignored. Overall, the line intensities in this new database are about 8% weaker than those quoted presently in the HITRAN (https://hitran.org/) or GEISA (https://geisa.aeris-data.fr/) databases. Our final linelist for HNO3 at 5.8 µm is provided as a supplement to this paper. It includes lines from the ν2 band together with those of the ν2+ν9−ν9, ν2+ν6−ν6, and ν2+ν7−ν7 associated hot bands that were generated during the first part of this study, described in the companion paper.

High-Resolution Spectra of the ν2 + ν4 (F1,F2) and 2ν4 (F2) Bands of Deuterated Silane 28SiD4

High-Resolution Spectra of the ν2 + ν4 (F1,F2) and 2ν4 (F2) Bands of Deuterated Silane 28SiD4

Measurements and calculations of xenon broadening and shift parameters of water vapour transitions for ν1 + ν2 + ν3 band

The water vapour line broadening and shifting of 72 lines in the ν1 + ν2 + ν3 vibrational band of H2O (in the 8603–8997 cm−1 spectral region) induced by xenon pressure were measured with a Bruker IFS HR FTIR spectrometer. These measurements were performed at room temperature, at a spectral resolution of 0.01 cm−1 and over a wide range of Xe pressure. The broadening and shift coefficients were also calculated using a semi-classical method. The intermolecular potential was taken as the sum of the anisotropic atom–atom potential and the effective vibrationally and rotationally dependent isotropic Lennard–Jones potential.The measured coefficients γ and δ were combined with data from the literature on the ν2, ν1, ν3, 2ν1 + 2ν3, 2ν1 + 2ν2 + ν3, and 3ν1 + ν3 bands, and optimal sets of potential parameters were found that gave the best agreement with the measured broadening coefficients. A strong influence of the imaginary part of the scattering matrix on the calculated values of the γ and δ coefficients was observed. The results were compared with those for He-, Ar-, and Kr-broadenings. The measured broadening coefficients were fitted to empirical expressions. The calculated values of the γ and δ coefficients were compared statistically to the measured values.

Rovibrational analysis of the [formula omitted] and 2[formula omitted][formula omitted] bands of deuterated formaldoxime (CH2NOD) by high-resolution synchrotron FTIR spectroscopy

The high-resolution Fourier transform infrared (FTIR) spectrum of the ν12 band and its hot band 2ν12-ν12 of deuterated formaldoxime (CH2NOD) was recorded at the far-IR beamline of Australian Synchrotron with an unapodized resolution of 0.00096 cm−1 in the 230–350 cm−1 region. A total of 1456 infrared transitions of the ν12 band was fitted using the Watson's A-reduced and S-reduced Hamiltonians in the Ir representation with root-mean-square (rms) deviations of 0.000237 and 0.000262 cm−1 respectively. Furthermore, 483 infrared transitions of the 2ν12-ν12 band were fitted using both A-reduced and S-reduced Hamiltonians in the Ir representation with rms deviation of 0.000186 cm−1. From this rovibrational analysis, the rovibrational constants of the v12 = 1 state up to sextic terms were derived for the first time. The band centers of the ν12 band of CH2NOD were found to be 303.319556(15) and 303.319553(18) cm−1 in the A-reduced and S-reduced Hamiltonians respectively, while band centers of 2ν12-ν12 were 296.620976(67) and 296.620976(67) cm−1 respectively. The rovibrational constants of the ground state of CH2NOD in the A-reduced and S-reduced Hamiltonians were obtained for the first time through the fitting of 608 ground state combination differences (GSCDs) derived from the infrared transitions of the ν12 band, together with 11 previously reported microwave frequencies. The rms deviations of the GSCD fit was 0.000318 and 0.000319 cm−1 in the A-reduced and S-reduced Hamiltonians respectively. Additionally, rotational constants and higher order centrifugal distortion terms of the ground, v12 = 1, and v12 = 2 states of CH2NOD were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set, for comparison with the experimental results. The calculated and experimental rovibrational constants of CH2NOD for the ground, v12 = 1, and v12 = 2 states are in close agreement.

First analysis of the ν2+ν7 and ν2+ν9 and ν2+ν6 combination bands of HNO3: evidence of perturbations due to large amplitude OH torsion in the 2191 excited state

This paper is the first of two back-to-back works, whose goal is to update the existing line positions and intensities spectroscopic parameters for the 5.8 µm region of nitric acid in the HITRAN or GEISA spectroscopic databases. This first study is devoted to the generation of first linelists for the ν2+ν9-ν9, ν2+ν7-ν7 and ν2+ν6-ν6 hot bands in the 5.8 µm region, whereas the second study will concern the positions and intensities for the ν2 band centred at 1709.567 cm−1. High-resolution Fourier transform spectra were recorded in the 5.8 µm and in the 4.2–4.6 µm spectral ranges. The identification of the ν2+ν9, ν2+ν7 and ν2+ν6 bands of HNO3 at 2165.0036, 2285.9657 and 2351.216 cm−1, respectively, was performed, and several assignments were confirmed by searching for ν2+ν9-ν9 and ν2+ν7-ν7 transitions within those of ν2 at 5.8 µm. Both ν2+ν6 and ν2+ν9 bands are highly perturbed. Surprisingly, both ν2+ν9 and ν2+ν9-ν9 bands exhibit large amplitude torsional splittings of ∼0.043 cm−1. This is presumed to be due to the existence of an anharmonic resonance that couples together the 2191 energy levels with those of a dark state involving high excitation in the ν9 large amplitude OH torsional mode.

Temperature-dependence exponents for CH3I-N2 line-broadening coefficients

Temperature-dependence exponents of the traditional power law relating line-broadening coefficients at experimental and reference temperatures are deduced for CH3I-N2 lines in the ν6 band from theoretical estimates in the temperature interval 200–400 K recommended for HITRAN. Perfectly linear fits in log-log coordinates indicate that this simple law is sufficient and more advanced models such as the double-power law are not applicable. Calculations are performed by a semi-empirical method employing room-temperature-adjusted model parameters which remain valid for other temperatures. Results are provided for all six sub-branches of the considered band and cover a large range of quantum numbers (0 ≤ J ≤ 70, K ≤ 20) requested typically by spectroscopic databases. In the absence of measurements at not-room temperatures, these data can be extremely useful for atmospheric applications involving methyl iodide, in particular for the terrestrial atmosphere. Given the negligible vibrational dependence of nitrogen-broadened CH3I line widths, the values computed for the ν6 fundamental can be safely used for other parallel and perpendicular bands.

Synthesis and Characterisation of Luminescent [CrIII 2 L(μ-carboxylato)]3+ Complexes with High-Spin S=3 Ground States (L=N6 S2 donor ligand).

The synthesis, structure, magnetic, and photophysical properties of two dinuclear, luminescent, mixed‐ligand [CrIII 2L(O2CR)]3+ complexes (R=CH3 (1), Ph (2)) of a 24‐membered binucleating hexa‐aza‐dithiophenolate macrocycle (L)2− are presented. X‐ray crystallographic analysis reveals an edge‐sharing bioctahedral N3Cr(μ‐SR)2(μ 1,3‐O2CR)CrN3 core structure with μ 1,3‐bridging carboxylate groups. A ferromagnetic superexchange interaction between the electron spins of the Cr3+ ions leads to a high‐spin (S=3) ground state. The coupling constants (J=+24.2(1) cm−1 (1), +34.8(4) cm−1 (2), H=−2JS1S2) are significantly larger than in related bis‐μ‐alkoxido‐μ‐carboxylato structures. DFT calculations performed on both complexes reproduce both the sign and strength of the exchange interactions found experimentally. Frozen methanol‐dichloromethane 1 : 1 solutions of 1 and 2 luminesce at 750 nm when excited into the 4LMCT state on the 4A2 → 2T1 (ν2) bands (λexc=405 nm). The absolute quantum yields (Φ L) for 1 and 2 were found to be strongly temperature dependent. At 77 K in frozen MeOH/CH2Cl2 glasses, Φ L=0.44±0.02 (for 1), Φ L=0.45±0.02 (for 2).

Analysis of the High-Resolution Spectrum of Molecules in Doublet Electronic States: Fundamental ν3 Band of Chlorine Dioxide (16O35Cl16O) in the Ground Electronic State X 2B1

Analysis of the High-Resolution Spectrum of Molecules in Doublet Electronic States: Fundamental ν3 Band of Chlorine Dioxide (16O35Cl16O) in the Ground Electronic State X 2B1

Determination of temperature-dependent Fermi resonance in acetonitrile-water binary solution by two-dimensional correlation Raman spectroscopy.

Acetonitrile (AN), as an organic solvent, has a wide range of applications. The C≡N stretching vibration mode (ν2) and the combination mode (ν3 + ν4) are coupled by Fermi resonance (FR). In this work, the phase transition and the interaction mechanism of the 60% AN-water binary solution (AN-Water) were analyzed by calculating FR parameters and two-dimensional correlation Raman spectroscopy (2DCRS). The change in the ν2 band and the base bands ν3 and ν4 caused energy transfer by anharmonic interaction, which led to a change in FR parameters. With a reduced temperature, the energy transfer was caused by microheterogeneity and the energy transfer effect (293-273K), the phase separation (263-233K), and the phase transition of AN (223-173K). The 2DCRS and Gaussian deconvolution provided more information on FR, which revealed the interaction mechanism of the Fermi doublet. The polarity and binding modes of molecules provided a new perspective for analyzing the transmission of electrons and ions in the electrolyte at different temperatures.

The vibrational properties of benzene on an ordered water ice surface

ABSTRACT We present a hybrid CCSD(T) + PBE-D3 approach to calculating the vibrational signatures for gas-phase benzene and benzene adsorbed on an ordered water ice surface. We compare the results of our method against experimentally recorded spectra and calculations performed using PBE-D3-only approaches (harmonic and anharmonic). Calculations use a proton ordered XIh water ice surface consisting of 288 water molecules, and results are compared against experimental spectra recorded for an ASW ice surface. We show the importance of including a water ice surface into spectroscopic calculations, owing to the resulting differences in vibrational modes, frequencies, and intensities of transitions seen in the IR spectrum. The overall intensity pattern shifts from a dominating ν11 band in the gas-phase to several high-intensity carriers for an IR spectrum of adsorbed benzene. When used for adsorbed benzene, the hybrid approach presented here achieves an RMSD for IR active modes of 21 cm−1, compared to 72 cm−1 and 49 cm−1 for the anharmonic and harmonic PBE-D3 approaches, respectively. Our hybrid model for gaseous benzene also achieves the best results when compared to experiment, with an RMSD for IR active modes of 24 cm−1, compared to 55 cm−1 and 31 cm−1 for the anharmonic and harmonic PBE-D3 approaches, respectively. To facilitate assignment, we generate and provide a correspondence graph between the normal modes of the gaseous and adsorbed benzene molecules. Finally, we calculate the frequency shifts, Δν, of adsorbed benzene relative to its gas-phase to highlight the effects of surface interactions on vibrational bands and evaluate the suitability of our chosen dispersion-corrected density functional theory.

Effects of sintering temperature on microstructure, initial permeability and electric behaviour of Ni-Mn-Zn ferrites

The effects of sintering temperature on microstructure, initial permeability, and electrical behaviour of Ni0.5-xMnxZn0.5Fe2O4 (0.0 < x < 0.5) prepared using the precursor combustion method have been investigated. X-ray diffraction analysis confirmed the single phase cubic spinel structure of Ni0.5-xMnxZn0.5Fe2O4 (0.0 < x < 0.4) compositions sintered at 1100 °C. The Mn2+ substituent preferentially occupies tetrahedral sites as indicated by the Rietveld analysis and the increase in the IR absorption frequency of ν1 band with increasing Mn substitution. The SEM measurements have revealed homogeneous microstructures of the ferrites with narrow grain size distribution in the range 0.93μm–1.86 μm. Mössbauer spectra exhibit a superposition of two Zeeman sextets for the compositions x ≤ 0.2, a superposition of two Zeeman sextets, and a paramagnetic doublet for the compositions, x = 0.3 and 0.4, and one sextet and single quadrupole doublet for a composition, x = 0.5. The activation energy in the range 0.258 eV–0.612 eV suggests a polaron hopping type conduction mechanism in all the sintered ferrites. The dielectric constant in the range 0.057–55.21 and lower dielectric loss (10−2) imply better stoichiometry and homogeneity. The initial permeability increases at lower Mn substitution (x = 0.2) and exhibits a decrease as the Mn substitution increases. The dc resistivity, dielectric constant, and initial permeability values suggest the suitability of these ferrites for high frequency device applications.

Beryl crystal chemistry and trace elements: Indicators of pegmatite development and fractionation (Damara Belt, Namibia)

The study reveals the relationships between crystal-chemical and genetic properties of beryl from several rare-element granitic pegmatites of the LCT family from the Damara Belt, Namibia. Based on their chemical compositions, the studied beryl samples can be divided into two groups. Beryl from the first group (the Engelbrecht's and Etusis pegmatites) is poor in Fe, Mg and Mn; however, slightly enriched in Zn and alkali elements (Na > Li, Rb, Cs). The samples from the second group (Kuduberge and Tsaobismund) are slightly enriched in Fe and Mg, in which they are mostly charge-balanced by Na, while other octahedral and channel constituents are negligible. The affinity of the first group of beryl to the dominant tetrahedral substitution is manifested in cell dimensions and the c/a ratio. Based on Raman and infrared spectroscopy, the Kuduberge and Tsaobismund samples have a very similar position and intensity of water FTIR bands, indicating the presence of both water types in the channels. The Englebrecht's sample is similar, however, the Etusis sample exhibits a shift of H2O II ν1 band, which could be attributed to a smaller Na content and strong dominance of doubly coordinating water. Our results indicate preferential occupancy of Na in the octahedral Na + (Fe,Mg)2+ = + Al substitution, which is typical for beryl from less fractionated pegmatites (Kuduberge and Tsaobismund), however, Na can also be a part of the complex tetrahedral substitution found in Englebrecht's beryl. Higher concentrations of Mn, Sc and Ti indicate a less fractionated genetic environment due to their affinity to Mg and Fe2+, whereas Cs, Rb and Zn prefer tetrahedral substitution, which is typical in highly evolved pegmatites.

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

This paper describes the updates of the line positions and intensities for the carbon dioxide transitions in the 2020 edition of the HITRAN spectroscopic database. The new line list for all 12 naturally abundant isotopologues of carbon dioxide replaces the previous one from the HITRAN2016 edition. This update is primarily motivated by several issues related to deficient HITRAN2016 line positions and intensities that have been identified from laboratory and atmospheric spectra. Critical validation tests for the spectroscopic data were carried out to find problems caused by inaccuracies in CO2 line parameters. New sources of data were selected for the bands that were deemed problematic in the HITRAN2016 edition. Extra care was taken to retain the consistency in the data sources within the bands. The comparisons with the existing theoretical and semi-empirical databases (including ExoMol, NASA Ames, and CDSD-296) and with available experimental works were carried out. The HITRAN2020 database has been extended by including additional CO2 bands above 8000 cm−1, and magnetic dipole lines of CO2 were introduced in HITRAN for the first time by including the ν2+ν3 band in the 3.3-µm region. Although the main topic of this article is line positions and intensities, for consistency a recent algorithm for the line-shape parameters proposed in Hashemi et al. JQSRT (2020) was reapplied (after minor revisions) to the line list.