Spectroscopie de Fourier a haute resolution d'especes instables diatomiques entre 2,5 et 25 micrometres. Contribution theorique et experimentale a la determination de la fonction moment dipolaire. Application a SH et OH

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 81171 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

The Vibrational Spectra of VinylPhosphine Revisited: Infrared and Theoretical Studies from CCSD(T) and DFT Anharmonic Potential

International audienceOn the grounds of CCSD(T) and DFT anharmonic potential and the use of a variational method, the vibrational spectra of vinylphosphine and one of its isopotomer are calculated and the IR spectra in the gas phase revisited between 600 and 6300 cm−1. The agreement between calculated and observed frequencies is fairly good for all fundamentals. These joint experimental and theoretical analyses allow us to assign (very) weak combinations and overtones bands observed in the regions revisited

Instrumentation for Fourier transform incoherent broadband cavity enhanced absorption spectroscopy of astrophysical anions

National audienc

High resolution spectroscopy of jet-cooled ionic species for atmospheric and astrophysical interest

Oral presentation :3M Nantes Doctoral School Day 2019 - At the heart of the matter:National audienc

Flow dynamics of a pulsed planar expansion

International audiencePlasma expansion sources are popular in molecular spectroscopy and in astrochemistry because they generate cold radicals and ions in detectable amounts. The dynamics of a planar flow generated by a pulsed discharge slit nozzle (PDN) have been numerically investigated for a variety of carrier gases seeded with various molecular species. The determination of the bulk flow characteristics is key to a comprehensive modeling of the plasma that is produced in PDN sources. It is found that the flow is established and stabilized within 75 and 25 μs when Ar and He are used as carrier gases, respectively. The residence time in the inter-electrode active region is found to be considerably shorter with He than with Ar gas carrier. The detection signal observed upon injection of astrochemical species such as polycylic aromatic hydrocarbons (PAHs) in moderate amounts in the carrier gas exhibits a non linear relation with the initial PAH concentration in the reservoir which is governed by the temperature. The local temperature along the flow axis can be predicted from the initial conditions using the isentropic equation. However, the local pressure and density behavior diverge significantly from an isentropic flow. Finally, implications for the characteristics of the plasma expansion are discussed to help design future laboratory simulations

Finding the signature of astrophysical anions using Fourier-transform incoherent broad-band cavity enhanced absorption spectroscopy (IBB-CEAS)

International audienc

Vibrational Spectra of Cyclopentadienylphosphine: Infrared and Theoretical Studies from DFT Anharmonic Potentials

International audienceBoth experimental and theoretical infrared investigations of cyclopentadienylphosphine (CpP) are reported. The infrared spectra (3500−500 cm-1) in the gas phase have been recorded at 0.5 cm-1 resolution. Infrared absorptions bands of the two lowest stable conformers were observed and assigned. Average integrated intensities of isolated and overlapping vibrational bands were also determined experimentally. The vibrational frequencies of the CpP system and its P-dideuterated isotopologue have been calculated by means of density functional theory. The Becke exchange functional and Lee−Yang−Parr correlation functional method with a combination of the two basis sets, namely 6-31+G(d,p) and the correlation-consistent triple-ζ cc-pVTZ set of Dunning, were used. Hybrid B3LYP/B3LYP//cc-pVTZ/6-31+G(d,p) anharmonic frequencies of the fundamental, overtone, and combination transitions were calculated in the 3500−200 cm-1 area with the use of a variational approach, implemented in the P_Anhar_v1.1 code, to assign the experimental data for each conformer

Anharmonic treatment of vibrational resonance polyads--the diborane: a critical case for numerical methods

International audienceBased on accurate computational results, the IR spectra of diborane B2H6 and its deuterated derivative B2D6 were experimentally revisited to reconsider or complete their band assignments. A pure, variational approach, developed in both mechanical and electrical anharmonicities, was applied to study the diborane molecule for which many uncertainties remain in the spectral IR assignment. This work, together with all the experiments on this system over recent decades, shows the difficulty of interpreting the spectral data, making it a "benchmark" ideal for testing the mathematical approaches for the implementation of vibrational codes

Computational fluid dynamic simulation of the supersonic CO2 flow during champagne cork popping

International audienceBehind the iconic "pop! " accompanying the uncorking of a champagne bottle hides a gas flow of surprising complexity. Its modeling is made delicate by its supersonic nature, its interaction with the cork stopper, the eminently unsteady character of the flow escaping from the bottle, and the continuous change of the geometry of the computational flow domain due to the displacement of the cork. Computational fluid dynamics (CFD) simulations revealed the formation, evolution, and dissipation of shock wave patterns during the first millisecond following champagne cork popping. A first crown-shaped shock wave pattern develops radially, which is then followed by the formation of a detached shock wave, or bow shock, induced by the presence of the cork in the axial path of the supersonic gas flow. Moreover, the good agreement between the position of the bow shock previously observed through high-speed imaging and that determined through CFD simulations argues in favor of the numerical method used to describe the ejection of the gas mixture expelled from the bottleneck immediately after the cork popping process. Published under an exclusive license by AIP Publishing

Line shape in a free-jet hypersonic expansion investigated by cavity ring-down spectroscopy and computational fluid dynamics

International audienceExperiments are carried out for spectroscopic studies using hypersonic jet of carbon monoxide seeded in argon as a carrier gas. Probing of this jet using cavity ring-down spectroscopy revealed a double peak structure for various absorption lines. Flow field simulation using computational fluid dynamics is used to understand the shape of such lines integrated over line of sight. Absorption contribution from warmer non-isentropic part of the jet, owing to its transverse velocity variation, is found responsible for those line shapes