High-resolution spectroscopy and analysis of the nu(1)/nu(3) stretching dyad of osmium tetroxide

Import OPTIWOSInternational audienceOsO4 is a heavy tetrahedral molecule that may constitute a benchmark for quantum chemistry calculations. Its favorable spin statistics (due to the zero nuclear spin of oxygen atoms) is such that only A(1) and A(2) rovibrational levels are allowed, leading to a dense, but quite easily resolved spectrum. Most lines are single ones, instead of complex line clusters as in the case of other heavy spherical-tops like SF6, for instance. It is thus possible to fully assign and fit the spectrum and to obtain precise experimental effective molecular parameters. The strong v(3) stretching fundamental has been studied a long time ago as an isolated band [McDowell RS, Radziemski LJ Flicker H, Galbraith HW, Kennedy RC, Nereson NG, et al. Journal of Chemical Physics 1978;88:1513-21; Bobin B, Valentin A. Henry L Journal of Molecular Spectroscopy 1987:122:229-41]. We reinvestigate here this region and perform new assignments and effective Hamiltonian parameter fits for the four main isotopologues ((OsO4)-Os-192, (OsO4)-Os-190, (OsO4)-Os-189, (OsO4)-Os-188), by considering the nu(1)/nu(3) stretching dyad. A new experimental spectrum has been recorded at room temperature, thanks to a Bruker IFS 125 HR interferometer and using a natural abundance OsO4 sample. Assignments and analyses were performed thanks to the SPVIEW and XTDS softwares, respectively [Wenger Ch, Boudon V. Rotger M. Sanzharov M, Champion J-P. Journal of Molecular Spectroscopy 2008;251:102-13]. We provide precise effective Hamiltonian parameters, including band centers and Coriolis interaction parameters. We discuss isotopic shifts and estimate the band centers for the three minor isotopologues ((OsO4)-Os-187, (OsO4)-Os-186, (OsO4)-Os-184). The Q branches of the first two of them are clearly identified in the experimental spectrum

Strong thermal nonequilibrium in hypersonic CO and CH4 probed by CRDS

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High-resolution stimulated Raman spectroscopy and analysis of the n1 band of osmium tetroxide

We present the first high-resolution stimulated Raman study of osmium tetroxide (OsO4). Lines from the n1 totally symmetric stretching fundamental have been assigned. These data together with the infrared assignments of the n3 band previously recorded (M. Louviot et al., J. Quant. Spectrosc. Radiat. Transfer, 2012, 113, 119–127) allowed a refinement of the analysis of the n1/n3 stretching dyad. We found that the n1 band has an unusual positive isotopic shift of approximately 0.32 cm 1 /amu, which gives further evidence that the stretching dyad should be perturbed by a complex nearby bending band polyad. This work is part of a global effort to analyze all fundamental bands of OsO4 to obtain a more precise experimental value of the ground state bond length for this heavy metal-containing molecule. The result could serve as a benchmark for high-level quantum chemistry calculations. Copyright © 2012 John Wiley & Sons, Ltd.D.B.P. and R.Z.M. acknowledge the financial support of the Ministry of Science and Innovation through research grant no. FIS2009-08069.Peer Reviewe

High enthalpy source dedicated to quantitative infrared emission spectroscopy of gas flows at elevated temperatures

International audienceThe 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. © 2019 Author(s)

CH₄,C₂H₄, SF₆ and CF₄ Calculated Spectroscopic Databases for the Virtual Atomic and Molecular Data Centre

<p>Two spectroscopic relational databases, denoted MeCaSDa and ECaSDa, have been implemented for methane and ethene, and included in the VAMDC (Virtual Atomic and Molecular Data Centre, http://portal.vamdc.eu/vamdc portal/home.seam)¹. These databases collect calculated spectroscopic data from the accurate analyses previously performed for the electronic ground state of methane, ethene, and some of their isotopologues: ¹²CH₄, ¹³CH₄, and ¹²C₂H₄². Both infrared absorption and Raman scattering lines are included. The polyad structures are reported and the transitions are precisely described by their energy, their intensity, and the full description of the lower and upper states involved in the transitions.</p> <p>Very recently, we also built on the same model two new databases, named SHeCaSDa and TFMeCaSDa for the SF₆and CF₄ greenhouse gas molecules, respectively.</p> <p>The relational schemas of these four databases are equivalent and optimized to enable the better compromise between data retrieval and compatibility with the XSAMS (XML Schema for Atoms, Molecules, and Solids) format adopted within the VAMDC European project.</p