Search

We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν2 mode spectrum of methane (CH4). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000 cm−1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH4 ν2 CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, Δ J = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH4 chemistry is demonstrated in a laboratory CH4/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O2), carbon dioxide (CO2), and molecular hydrogen (H2), along with CH4. Fundamental physicochemical processes, such as H2 production via CH4 pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH4 v2 CRS thermometry, and we validate it against CO2 CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH4-rich environments, e.g., in plasma reactors for CH4 pyrolysis and H2 production.

We use a Fourier transform spectrometer based on a difference frequency generation optical frequency comb to measure high-resolution, low-pressure, room-temperature spectra of methane in the 1250 - 1380 cm$^{-1}$ range. From these spectra, we retrieve line positions and intensities of 678 lines of two isotopologues: 157 lines from the $^{12}$CH${_4}$ ${\nu}$${_4}$ fundamental band, 131 lines from the $^{13}$CH${_4}$ ${\nu}$${_4}$ fundamental band, as well as 390 lines from two $^{12}$CH${_4}$ hot bands, ${\nu}$${_2}$ + ${\nu}$${_4}$ - ${\nu}$${_2}$ and 2${\nu}$${_4}$ - ${\nu}$${_4}$. For another 165 lines from the $^{12}$CH${_4}$ ${\nu}$${_4}$ fundamental band we retrieve line positions only. The uncertainties of the line positions range from 0.19 to 2.3 MHz, and their median value is reduced by a factor of 18 and 59 compared to the previously available data for the $^{12}$CH${_4}$ fundamental and hot bands, respectively, obtained from conventional FTIR absorption measurements. The new line positions are included in the global models of the spectrum of both methane isotopologues, and the fit residuals are reduced by a factor of 8 compared to previous absorption data, and 20 compared to emission data. The experimental line intensities have relative uncertainties in the range of 1.5 - 7.7%, similar to those in the previously available data; 235 new $^{12}$CH${_4}$ line intensities are included in the global model.

We use comb-based Fourier transform spectroscopy to record high-resolution spectra of 12CH4 and 13CH4 from 1250 to 1380 cm-1. We obtain line positions and intensities of 4 bands with uncertainties of ~450 kHz and ~3%, respectively, which we use to improve a global fit of the effective Hamiltonian.

The infrared absorption of the ν

This paper describes the 2020 release of the GEISA database (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information), developed and maintained at LMD since 1974. GEISA is the reference database for several current or planned Thermal and Short-Wave InfraRed (TIR and SWIR) space missions IASI (Infrared Atmospheric Sounding Interferometer), IASI-NG (IASI New Generation), MicroCarb (Carbon Dioxide Monitoring Mission), Merlin (MEthane Remote sensing LIdar missioN). It is actually a compilation of three databases: the “line parameters database”, the “cross-section sub-database” and the “microphysical and optical properties of atmospheric aerosols sub-database”. The new edition concerns only the line parameters dataset, with significant updates and additions implemented using the best available spectroscopic data. The GEISA-2020 line parameters database involves 58 molecules (145 isotopic species) and contains 6,746,987 entries, in the spectral range from 10−6 to 35877 cm−1. In this version, 23 molecules have been updated (with 10 new isotopic species) and 6 new molecules have been added (HONO, COFCl, CH3F, CH3I, RuO4, H2C3H2 (isomer of C3H4)) corresponding to 15 isotopic species. The compilation can be accessed through the AERIS data and services center for the atmosphere website (https://geisa.aeris-data.fr/), with the development of a powerful graphical tool and convenient searching, filtering, and plotting of data using modern technologies (PostgreSQL database, REST API, VueJS, Plotly). Based on four examples (H2O, O3, O2 and SF6), this paper also shows how the LMD in house validation algorithm SPARTE (Spectroscopic Parameters And Radiative Transfer Evaluation) helps to evaluate, correct, reject or defer the input of new spectroscopic data into GEISA and this, thanks to iterations with researchers from different communities (spectroscopy, radiative transfer).

International audience

This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of the VAMDC e-infrastructure. We analyse the past 10 years of VAMDC development and operation, and assess their impact both on the field of atomic and molecular (A&amp, M) physics itself and on heterogeneous data management in international cooperation. The highly sophisticated VAMDC infrastructure and the related databases developed over this long term make them a perfect resource of sustainable data for future applications in many fields of research. However, we also discuss the current limitations that prevent VAMDC from becoming the main publishing platform and the main source of A&amp, M data for user communities, and present possible solutions under investigation by the consortium. Several user application examples are presented, illustrating the benefits of VAMDC in current research applications, which often need the A&amp, M data from more than one database. Finally, we present our vision for the future of VAMDC.

International audience; We report the current status of our calculated spectroscopic relational databases. They contain line lists for specific molecules, that result from recently published spectroscopic analyses. The two original databases, denoted MeCaSDa (CH 4) and ECaSDa (C 2 H 4), have been greatly improved with the addition of new calculated lines. Then, five new databases, TFMeCaSDa (CF 4), SHeCaSDa (SF 6), GeCaSDa (GeH 4), RuCaSDa (RuO 4) and TFSiCasDa (SiF 4) were deployed based upon the same model. These databases are developed in the framework of the international consortium VAMDC (Virtual Atomic and Molecular Data Centre, http://vamdc.org) and are also part of the Dat@OSU project (http://dataosu.obs-besancon.fr).

International audience; The study and analysis of heavy spherical-top molecules is often not straightforward. The presence of hot bands and of many isotopologues can lead to a high line congestion very difficult for assignment. In this work, using a low-order model we have derived very simple isotopic relations in order to determine initial parameters of the analysis. We also show that an identical approach can be used for XY 4 and XY 6 molecules and all these results are illustrated by the comparison of numerical computations and experiments.

International audience; Sulfur hexafluoride is a powerful greenhouse gas of industrial origin. Remotesensing detection of this heavy species requires a detailed knowledge of its infrared absorption spectra that features many hot bands at room temperature. It is thus necessary to study many of its rovibrational levels which are implied in such hot band transitions. Based on our previous results reporting global fits of many rovibrational bands [M. Faye at al., J. Quant. Spectrosc. Radiat. Transfer 190, 38-47 (2017)], we present here detailed analyses of three combination bands, namely ν 1 + ν 4 , ν 2 + ν 6 and ν 5 + ν 6. The ν 2 + ν 6 combination band has been already investigated some years ago, but the present analysis represents a strong improvement; the two other bands are analyzed in detail for the first time. The results contribute to improve the simulation of hot bands in the strongly absorbing ν 3 and ν 4 regions and they have been used to update the SHeCaSDa database (http://vamdc.icb.cnrs.fr/PHP/shecasda.php).

Silicon tetrafluoride (SiF4) is a trace component of volcanic gases. However, a better knowledge of spectroscopic parameters is needed for this molecule in order to derive accurate concentrations. This motivated FTIR measurements with high-spectral resolution (0.001 cm − 1 ) and an extensive study of its infrared absorption bands, including the fundamentals and overtone and combinations. We present here a detailed analysis and modeling of the strongly absorbing ν3and ν4 fundamental bands, for the three isotopologues in natural abundance: 28SiF4 (92.23 %), 29SiF4 (4.67 %) and 30SiF4 (3.10 %). It includes a global fit with consistent parameter sets for the ground and excited states. In particular, all existing rotational line data have been included. The 2ν4 band of 28SiF4 could also be analyzed in detail. A first fit of the dipole moment derivative for the ν3 band for 28SiF4 has been performed, along with two independent estimates of the integrated band intensity; the results are consistent with literature values, around 690 km/mol. The isotopic dependence of band centers and Coriolis parameters has also been studied. TFSiCaSDa, a new database of cross sections and calculated lines for the ν3 band of SiF4, has been set up.

International audience; We present a modified version of the Judd-Ofelt theory, which describes the intensities of f-f transitions for trivalent lanthanide ions (Ln3+) in solids. In our model, the properties of the dopant are calculated with well-established atomic-structure techniques, while the influence of the crystal-field potential is described by three adjustable parameters. By applying our model to europium (Eu3+), well-known to challenge the standard Judd-Ofelt theory, we are able to give a physical insight into all the transitions within the ground electronic configuration, and also to reproduce quantitatively experimental absorption oscillator strengths. Our model opens the possibility to interpret polarized-light transitions between individual levels of the ion-crystal system.

Silicon tetrafluoride (Si F 4 ) 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 ν 3 and ν 4 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 28 Si F 4 , now including the v 1 = 1 and v 2 = 1 states, by adding to the global analysis the newly measured ν 2 , ν 1 − ν 4 , and ν 4 − ν 2 bands near 264, 412, and 125 cm−1, respectively. Nearly 20 000 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, r e ( SiF 4 ) = 1 . 5516985 ( 30 ) A. Some new band intensity estimates allow us to update our Si F 4 calculated spectroscopic database.

Spherical-top tetrahedral species like CH 4 , SiH 4 , CF 4 , …possess no permanent dipole moment. Therefore, probing their pure rotation spectrum is very challenging since only a very weak dipole moment can be induced by centrifugal distortion and/or rovibrational interaction. If some Q branch lines have been recorded thanks to microwave techniques, R branch lines in the THz region have been poorly explored until recently. In previous studies, we have reported the pure rotation THz spectrum of cold and hot band lines of methane recorded at the SOLEIL Synchrotron facility. Here, we present the first recorded THz spectrum of the R branch of CF 4 , a powerful greenhouse gas, in its v 3 = 1 state. This Fourier transform spectrum covers the R ( 20 ) to R ( 37 ) line clusters, in the 20–37 cm −1 spectral range. It was recorded thanks to a 150 m multiple path cell at room temperature. We could estimate the vibration-induced dipole moment value and also include the recorded line positions in a global fit of many CF 4 transitions.

Sulfur hexafluoride is a greenhouse gas with a long lifetime in the atmosphere and an important tracer for air mass circulation atmospheric models. The IR spectrum of this heavy species, however, features many hot bands at room temperature (at which only 30% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v 6 and v 5 = 1 vibrational states. Using a cryogenic long path cell with variable optical path length and temperatures regulated between 168 and 163 K, coupled to Synchrotron Radiation and a high resolution interferometer, Doppler-limited spectra of the very weak ν 3 + ν 5 band near 1450 cm−1 have been recorded. Low temperature was used to limit the presence of hot bands and simplify the rotational structure. The spectrum has been analyzed thanks to the XTDS software package. Combining with the results obtained previously on the weak difference bands in the far infrared region involving the v 5 = 1 states, we are thus able to use the tensorial model to propose a spectroscopic parameter set for modelling the strong ν 3 + ν 5 - ν 5 hot band. The model constitutes a coherent set of molecular parameters and enable spectral simulation for atmospheric sounding. Test simulations at different temperatures and in nitrogen broadened conditions are presented and compared with new experimental cross section data for the absorption region relevant for atmospheric quantification.

The ν 3 band of the 36 SF 6 isotopologue has been recorded in natural abundance (0.02%) at 153 K-temperature with doppler limited resolution, using a Fourier transform spectrometer. For the first time, the high resolution analysis of this band is performed thanks to the Dijon tensorial formalism model. The effective Hamiltonian parameters are determined and the interest of studying rare SF 6 isotopologues is discussed.

Several Doppler-limited rotational transitions of methane induced by centrifugal distortion have been measured with an unprecedented frequency accuracy using a THz photomixing synthesizer based on a frequency comb. Compared to previous synchrotron based FT-Far-IR measurements of Boudon et al. (Ref. [1] ), the accuracy of the line frequency measurements is improved by one order of magnitude; this yields a corresponding increase of two orders of magnitude to the weighting of these transitions in the global fit. The rotational transitions in the ν 4 ← ν 4 hot band are measured for the first time by the broad spectral coverage of the photomixing CW-THz spectrometer providing access up to R(5) transitions at 2.6 THz. The new global fit including the present lines has been used to update the methane line list of the HITRAN database. Some small, but significant variations of the parameter values are observed and are accompanied by a reduction of the 1- σ uncertainties on the rotational ( B 0 ) and centrifugal distortion ( D 0 ) constants.

CF4, or tetrafluoromethane, is a chemically inert and strongly absorbing greenhouse gas, mainly of anthropogenic origin. In order to monitor and reduce its atmospheric emissions and concentration, it is thus necessary to obtain an accurate model of its infrared absorption. Such models allow opacity calculations for radiative transfer atmospheric models. In the present work, we perform a global analysis (divided into two distinct fitting schemes) of 17 rovibrational bands of CF4. This gives a reliable model of many of its lower rovibrational levels and allows the calculation of the infrared absorption in the strongly absorbing ν3 region (1283 cm − 1 / 7.8 μm), including the main hot band, namely ν 3 + ν 2 − ν 2 as well as ν 3 + ν 1 − ν 1 ; we could also extrapolate the ν 3 + ν 4 − ν 4 absorption. This represents almost 92% of the absorption at room temperature in this spectral region. A new accurate value of the C–F bond length is evaluated to r e = 1.314860 ( 21 ) A. The present results have been used to update the HITRAN, GEISA and TFMeCaSDa (VAMDC) databases.

Sulfuryl fluoride (SO2F2) is of a fundamental interest due to its nearly tetrahedral symmetry, making it, thereby, an intermediate case between spherical and asymmetric-top molecules. It is also a widely-used insecticide and an atmospheric pollutant. A new high-resolution infrared spectrum of the ( ν 9 , ν 7 , ν 3 ) bending triad of SO2F2 in the 550 cm−1 region has been recorded at 165 K with a spectral resolution of 0.00102 cm−1 at the AILES beamline of the SOLEIL Synchrotron. Analysis has been performed in the O ( 3 ) ⊃ T d ⊃ C 2 v group chain using a specific model and programs based on tensorial formalism, group theory and vibrational extrapolation method. This model is adapted to the case of XY2Z2 asymmetric-top molecules with C 2 v symmetry developed by Rotger et al. (2002). This approach enables studying any rovibrational band or polyad with a systematic development of all rovibrational interactions. A total of 6058 IR lines has been assigned and fitted in position with a global root mean square deviation (RMS) of 0.484 × 10−3 cm−1. This result improves the previous analyses performed by Burger et al. (2002) and Rotger et al. (2006).

The rovibrational spectrum of Deuterobromochlorofluoromethane CDBrClF has been measured with a resolution of better than 0.001 cm−1 at room temperature with the Zurich Bruker IFS spectrometer prototype (ZP 2001) using a globar source, and with the Bruker prototype 2009 interferometer connected to the Swiss Light Source (SLS) synchrotron as a radiation source providing a resolution of 0.0007 cm−1 in the range 600–1100 cm−1. In addition CDBrClF has been measured at low rotational temperature (Trot = 15 K) with our diode laser supersonic jet setup around 748 cm−1 in the ν 5 region (resolution 0.0013 cm−1). The spectra of the two major isotopomers CD 79 Br 35 ClF and CD 81 Br 35 ClF have been analyzed within the ν 5 (CCl-stretch, ν 0 = 748.2998 cm−1 ( CD 79 Br 35 ClF ), ν 0 = 748.1541 cm−1 ( CD 81 Br 35 ClF )), ν 4 (CF-stretch, ν 0 = 1082.8116 cm−1 ( CD 79 Br 35 ClF ), ν 0 = 1082.7963 cm−1 ( CD 81 Br 35 ClF )) and ν 3 (DCF-bend, ν 0 = 918.3715 cm−1 ( CD 79 Br 35 ClF ), ν 0 = 918.0206 cm−1 ( CD 81 Br 35 ClF )) regions. A detailed rovibrational analysis of these bands is presented. A combined analysis of the ν 3 , ν 4 and ν 5 fundamental bands provides accurate rotational and quartic centrifugal distortion constants for the vibrational ground state and for the states ν 3 , ν 4 and ν 5 of CD 79 Br 35 ClF and CD 81 Br 35 ClF . The results are discussed in relation to intramolecular (ro)vibrational redistribution (IVR) and also possible experiments pertaining to the experimental detection of molecular parity violation.

This work describes the theoretical basis and implementation of the measurement of vibrational (Tvib) and rotational (Trot) temperatures in CH4 by fitting spontaneous Raman scattering spectra in the Pentad region. This method could be applied for thermal equilibrium temperature measurements applications, e.g. in combustion, or vibrational-rotational non-equilibrium applications, such as in plasma chemistry. The method of calculating these temperatures is validated against known temperature thermal equilibrium spectra up to 860 K from published data, giving an estimated relative error of 10%. This demonstrates that both the calculated stick spectrum and the algorithm to determine Tvib and Trot for CH4 is robust to 860 K, but we expect it is valid to 1500 K. Additionally, a number of non-equilibrium spectra generated with a pulsed microwave plasma are fitted to find Tvib and Trot, further demonstrating the applicability of this method in fitting non-equilibrium spectra.

International audience; e-PYTHEAS is a multidisciplinary project which combines theoretical and experimental work with exoplanet modelling applications. It sits on the frontier between molecular physics, theoretical chemistry and astrophysics. It aims at enhancing our understanding of the radiative properties of hot gaseous media to allow for improved analysis and interpretation of the large mass of data available on the thousands of exoplanets and exoplanetary systems known to date. Our approach is to use theoretical research validated by laboratory experiments and to then inject it into models of the atmospheres of the giant gaseous planets in the solar system and other planetary systems. This will help to analyse data and address essential questions on the formation and evolution of planetary systems, such as retrieved by ESA's M4 space mission ARIEL. Our consortium of 5 French laboratories and associated partners proposes to improve the existing high-temperature spectroscopy data for several molecular species detected in exoplanets. The provision of infrared (IR) laboratory data of methane, acetylene, ethylene and ethane, between 500 and 2500 K will help to refine thermal profiles and provide information on the gaseous composition, the hazes and their temporal variability. See the project's website: http://e-pytheas.cnrs.fr

New experimental high-resolution Fourier-Tansform infrared spectra of the infrared active fundamental ν2 band of sulfuryl fluoride SO2F2, have been recorded at a temperature of 193 K and at resolution of 0.00102 cm − 1 at the AILES (Advanced Infrared Line Exploited for Spectroscopy) beamline of the SOLEIL (Source Optimisee de Lumiere d’Energie intermediaire du LURE) Synchrotron facility. A detailed analysis has been performed both in line positions and intensities with the C2vTDS (Top Data System) program suite, based on the tensorial formalism developed in Dijon for quasi-spherical top molecules. The effective Hamiltonian was developed up to fourth order. The parameter of the effective dipole moment operator has been determined using the wavefunctions of the effective Hamiltonian operator. 2407 line positions have been measured with global root mean square deviation of about 0.19 × 10 − 3 cm − 1 . Using 71 lines intensities, we estimate the uncertainty on calculated line intensities to 10%. To the extent of our knowledge, this is the first time that an absolute intensity analysis has been carried out for sulfuryl fluoride.

The High Enthalpy Source (HES) is a novel high temperature source developed to measure infrared line-by-line integrated absorption cross sections of flowing gases up to 2000 K. The HES relies on a porous graphite furnace designed to uniformly heat a constant flow of gas. The flow compensates thermal dissociation by renewing continuously the gas sample and eliminating dissociation products. The flowing characteristics have been investigated using computational fluid dynamics simulation confirming good temperature uniformity. The HES has been coupled to a high-resolution Fourier transform spectrometer to record emission spectra of methane at temperatures ranging between 700 and 1400 K. A radiative model has been developed to extract absolute line intensities from the recorded spectra., SCOPUS: ar.j, info:eu-repo/semantics/published

The high resolution infrared spectra of GeH 4 in its natural abundance were recorded with a Bruker IFS125 HR Fourier transform infrared spectrometer at an optical resolution of 0.003 cm − 1 and analyzed in the region of 1400–2000 cm − 1 where the first bending overtone 2 ν 2 , 2 ν 4 and combinational ν 2 + ν 4 bands are located. Ro–vibrational line positions and energies of the 70 GeH 4 species were analysed for the first time and line positions and energies of the 72 GeH 4 and 74 GeH 4 species were improved considerably in comparison with the preceding studies. The numbers of 2316/2406/873/3007/2257 transitions with J max = 21/23/18/22/19 of the 2 ν 2 ( A 1 − and E − type sub–bands), 2 ν 4 ( A 1 − , E − and F 2 − type sub–bands) and ν 2 + ν 4 ( F 1 − and F 2 − type sub–bands) bands of the 70 GeH 4 , 72 GeH 4 , 73 GeH 4 , 74 GeH 4 , and 76 GeH 4 molecules were used in the joint weighted fit of experimentally assigned transitions with the Hamiltonian model which takes the resonance interactions between the seven, ( 0200 , A 1 ) , ( 0200 , E ) , ( 0101 , F 1 ) , ( 0101 , F 2 ) , ( 0002 , A 1 ) , ( 0002 , E ) and ( 0002 , F 2 ) , vibrational states into account. From our preceding studies 5563 hot band transitions were also taken into account. As the result of a joint fit, a set of 129 fitted parameters was obtained which reproduce the initial 16422 experimental (including “hot”) transitions of five isotopologues with the d rms = 3.26 × 10 − 4 cm − 1 . A line strength analysis of the 1697 experimentally recorded transitions of all species was made by the fit of their line shapes with the Hartmann-Tran profile and 13 effective dipole moment parameters were obtained from the weighted fit which reproduce the initial experimental line strengths with the d rms = 3.4 % . Self–broadening coefficients of 993 lines and self–shift coefficients of 674 lines were determined from the multi–spectrum analysis of these lines.

Germane is a tetrahedral molecule found in trace abundance in giant gas planets like Jupiter and Saturn. We have recently provided a database of calculated lines of the stretching fundamental bands in the 2100 cm − 1 region that is of high interest for planetology ( https://vamdc.icb.cnrs.fr/PHP/GeH4.php ). It is now necessary to study many rovibrational levels, including the lowest ones, in order to access the hot bands and thus to improve the model of the spectral region of interest for Jupiter, especially in the framework of the ongoing Juno mission. We present here a complete analysis and modeling of line positions and intensities in the ν 2 / ν 4 bending dyad region near 900 cm − 1 for all five germane isotopologues in natural abundance. Thanks to the high symmetry of the molecule, we use the tensorial formalism and group theory methods developed in the Dijon group, that allows us to provide a set of effective Hamiltonian and dipole parameters. The present study also leads to a refined value of the Ge–H equilibrium bond length of 1.51714(25) A. Finally, new calculated germane lines were derived and injected in the GeCaSDa database.

A new high-resolution infrared spectrum of the ν 2 band of SO2F2 centered at 849.46 cm−1 has been recorded with a resolution of 0.00102 cm−1 at the AILES beamline of SOLEIL Synchrotron facility. More than 1600 lines up to Jmax = 41 have been assigned and fitted in line position using a tensorial formalism adapted to the case of XY2Z2 asymmetric molecules developed as an extension of the usual one used for spherical tops (Rotger et al., 2002). The analysis has been performed in the O ( 3 ) ⊃ T d ⊃ C 2 v group chain, thanks to the C2vTDS program suite (Wenger et al., 2005). This approach allows a systematic development of rovibrational interaction to study any polyad of SO2F2 and makes easier global analysis. Compared to a previous study (Merke et al., 2006), the present fit uses less effective Hamiltonian parameters but we assigned lines up to a lower J value.

In this study, we report the first experimental measurements of spectral line shape parameters (self- and air-broadened Lorentz half-widths, pressure-shifts, and line mixing (via off-diagonal relaxation matrix elements) coefficients and their temperature dependences, where appropriate) for transitions in the 2ν 3 Q branch manifolds, Q(11)–Q(1) of methane ( 12 CH 4 ), in the 5996.5–6007-cm −1 region. The analysis included 23 high-resolution, high signal-to-noise laboratory absorption spectra recorded with the Bruker IFS-125HR Fourier transform spectrometer (FTS) at JPL. The experimental data were obtained using 12 C-enriched 12 CH 4 and dilute mixtures of 12 CH 4 in dry air in the 130–296 K range using a room-temperature long path absorption cell and, two custom-built coolable cells. In the analysis, an interactive multispectrum fitting software was employed where all the 23 spectra (11 self-broadened and 12 air-broadened) were fit simultaneously. By carefully applying reasonable constraints to the parameters for severely blended lines, we were able to determine a self-consistent set of broadening, shift and line mixing (relaxation matrix coefficients) parameters for CH 4 –CH 4 and CH 4 –air collisions. In the majority of cases, a quadratic speed dependence parameter common for all transitions in each Q( J ) manifold was determined. However, temperature dependences of the Q branch line mixing parameter could not be determined from the present data. Since no other experimental line shape measurements have been reported for this Q-branch, the present results are compared to available values in the HITRAN2012 database.

In this paper, we present the high resolution analysis of the weak ν 2 + ν 4 - ν 5 band of SF6 around 735 cm−1. The spectra were recorded on the AILES Beamline at the SOLEIL Synchrotron facility using a cryogenic multipass cell coupled to a Bruker 125HR spectrometer with a maximum resolution of 0.00102 cm−1. For this band, we worked with 4 mbar of SF6 at a temperature of 223 ± 2 K. The optical path length was fixed to 141 m and the spectrum recorded with 0.001 cm−1 of resolution. A new, cold spectrum of the ν 2 + ν 4 band was also collected at 153 K, 15-m path length, and 0.0015 cm−1 resolution. The analysis was performed by using the Dijon group XTDS and SPVIEW software, based on tensorial formalism. We achieved correct simulation and line position assignments of the ν 2 + ν 4 - ν 5 band, by gathering ν 2 + ν 4 data and ν 5 Raman data. We could assign 3553 transition for ν 2 + ν 4 - ν 5 with a standard deviation of 1.292 × 10 - 3 cm−1. This analysis also helped improve the v2 = v4 = 1 level and the v5 = 1 fundamental level v2 = v4 = 1.

High-resolution stimulated Raman spectra of13C2H4 in the regions of the ν2 and ν3 Raman active modes have been recorded at two temperatures (145 and 296 K) based on the quasi continuous-wave (cw) stimulated Raman spectrometer at Instituto de Estructura de la Materia IEM-CSIC in Madrid. A tensorial formalism adapted to X2Y4 planar asymmetric tops with D2h symmetry (developed in Dijon) and a program suite called D2hTDS (now part of the XTDS/SPVIEW spectroscopic software) were proposed to analyze and calculate the high-resolution spectra. A total of 103 and 51 lines corresponding to ν2 and ν3 Raman active modes have been assigned and fitted in wavenumber with a global root mean square deviation of 0.54 × 10−3 and 0.36 × 10−3 cm−1, respectively. Due to the fact that the Raman scattering effect is weak, we did not perform in this contribution the line intensities analysis. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, we report the vibration-rotation energy levels of methane (12CH4) calculated using the latest version of the global effective Hamiltonian developed in Dijon [B. AMYAY et al.. J. Chem. Phys., 148, 134–306 (2018)]. 238,429 vibration-rotation energy levels are calculated rotationally up to J = 50 and vibrationally up to the Tetradecad ( ≈ 6200 cm − 1 ). The corresponding wavefunctions mixings are also investigated in this work. The knowledge of both energy levels and wavefunctions mixings are essential for simulating high-resolution spectra of methane of astrophysical and atmospheric interests. An evidence of distinct regular and oscillatory contributions, is observed in the number of vibration-rotation levels of methane. This can be fully understood using the generating functions presented by Sadovskii and Zhilinskii [J. Chem. Phys. 103, 10–520 (1995)].

International audience; The experiment SPIRALES coupling a tunable infrared laser to a pulsed supersonic free jet has allowed us to reinvestigate the high-resolution absorption spectroscopy of the SF 6 dimer in the ν3 mode region under various experimental conditions: In addition to the SF 6 dimer spectrum so far reported, we demonstrate the existence of two new spectral features : i) one assigned to a second conformer of this species, characterized by a larger interatomic distance as well as ii) a complex (SF 6) 2-He.