A5039621618- Advanced Chemical Physics Studies
- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Spectroscopy and Laser Applications
- Molecular Spectroscopy and Structure
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Quantum, superfluid, helium dynamics
- Catalytic Processes in Materials Science
- Atomic and Molecular Physics
- Catalysis and Oxidation Reactions
- COVID-19 epidemiological studies
- Mass Spectrometry Techniques and Applications
- Gas Dynamics and Kinetic Theory
- Infection Control and Ventilation
- Combustion and Detonation Processes
- Photochemistry and Electron Transfer Studies
- Advanced Combustion Engine Technologies
- Analytical Chemistry and Chromatography
- Planetary Science and Exploration
- Free Radicals and Antioxidants
- COVID-19 impact on air quality
- Atmospheric and Environmental Gas Dynamics
- Rocket and propulsion systems research
- Air Quality and Health Impacts
Université de Rennes
2015-2024
Centre National de la Recherche Scientifique
2015-2024
Institut de Physique de Rennes
2015-2024
Département de Chimie Moléculaire
2015-2019
Générale-Beaulieu Clinic
2016-2018
University of Birmingham
2006-2008
Laboratoire d'Astrophysique de Bordeaux
2008
Laboratoire de Physique des Lasers, Atomes et Molécules
1991-2007
AlbaNova
2004
Western University
1994
This paper is a detailed critical review of the production processes and reactions N, N+, N+2, N++, N++2 relevance to Titan's atmosphere. The includes neutral, ion–molecule, recombination reactions. covers all possible active nitrogen species under atmospheric conditions, specifically N2 (A3Σ+u), N (4S), (2D), (2P), N+ (3P), (1D), N++2, N++ species, survey with N2, H2, D2, CH4, C2H2, C2H4, C2H6, C3H8 deuterated hydrocarbon analogs, as well N++. Production processes, lifetimes, quenching by...
The flowing afterglow technique, coupled with laser induced fluorescence (LIF) and vacuum ultraviolet (vuv) absorption spectroscopy, has been used to determine the fractional H-atom contributions, fH, product distributions for dissociative recombination of a series protonated ions (N2H+, HCO+, HCO+2, N2OH+, OCSH+, H2CN+, H3O+, H3S+, NH+4, CH+5 ) electrons. measurements were made at 300 K in two separate ways laboratories by (i) directly determining number density using vuv spectroscopy Lα...
We report combined studies on the prototypical S(1D2) + H2 insertion reaction. Kinetics and crossed-beam experiments are performed in experimental conditions approaching cold energy regime, yielding absolute rate coefficients down to 5.8 K relative integral cross sections collision energies as low 0.68 meV. They supported by quantum calculations a potential surface treating long-range interactions accurately. All results consistent excitation function behavior is explained terms of...
The predictivity of photochemical models Titan's atmosphere depends strongly on the precision and accuracy reaction rates. For many reactions, large uncertainty results from extrapolation rate laws to low temperatures. A few reactions have been measured directly at temperatures relevant atmosphere. In present study, we observed consequences reduced attributed these reactions. global model was improved, i.e., most species are predicted with lower factors. Nevertheless, high factors still...
The role of HO3 as a temporary reservoir atmospheric OH radicals remains an open question largely because the considerable uncertainty in value dissociation energy HO-O2 bond (D0) or, equivalently, standard enthalpy formation (Delta(f)H;{\overline{);\circ }}$$). Using supersonic flow apparatus, we have observed by means laser-induced fluorescence decay presence O2 at temperatures between 55.7 and 110.8 kelvin (K). Between 87.4 99.8 K, concentration approached nonzero long times, allowing...
In the last years, ultra-low temperature chemical kinetic experiments have demonstrated that some gas-phase reactions are much faster than previously thought. One example is reaction between OH and CH3OH, which has been recently found to be accelerated at low temperatures yielding CH3O as main product. This finding opened question of whether observed in dense core Barnard 1b could formed by CH3OH OH. Several models including this grain-surface processes developed explain abundance CH$_3$O...
The reactivity of methanol (CH3OH) toward the hydroxyl (OH) radical was investigated in temperature range 11.7-177.5 K using CRESU (French acronym for Reaction Kinetics a Uniform Supersonic Flow) technique. In present study, dependence rate coefficient OH + CH3OH reaction, k(T), has been revisited and additional experimental computational data are reported. New kinetic measurements were performed to fill existing gaps (<22 K, 22-42 88-123 K), reporting k(T < 20 K) first time. lowest ever...
We present a joint crossed molecular beam and kinetics investigation combined with electronic structure statistical calculations on the reaction of ground-state cyano radical, CN(X2Σ+), 1,3-butadiene molecule, H2CCHCHCH2(X1Ag), its partially deuterated counterparts, H2CCDCDCH2(X1Ag) D2CCHCHCD2(X1Ag). The studies indicate that proceeds via long-lived C5H6N complex, yielding C5H5N isomer(s) plus atomic hydrogen under single collision conditions as nascent product(s). Experiments 1,3-butadienes...
Abstract The chemical kinetics of neutral–neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry complex organic molecules in interstellar medium ( T ∼ 10–100 K). Scarce kinetic information currently available for these kinds < 200 K. In this work, we use Cinétique de Réaction en Ecoulement Supersonique Uniforme (CRESU; Reaction Kinetics Uniform Supersonic Flow) technique to measure first time rate coefficients k...
Rate constants were determined for the reactions of CH(X2Π,ν=0) with H2 and D2 relaxation CH(X2Π,ν=1) by D2. The method, employing pulsed laser photolysis to generate CH radicals laser-induced fluorescence observe their rate removal, was implemented between 744 86 K in heated cryogenically cooled cells from 295 13 a Cinétique de Réaction en Ecoulement Supersonique Uniforme (CRESU) apparatus. reaction CH(ν=0) 584 those removal CH(ν=1) 23 K. These show no dependence on total pressure mild...
A new flowing afterglow apparatus that utilizes a Langmuir probe/mass spectrometer to monitor both electron and ion decay in hydrogen plasma has been used measure the dissociative recombination rate coefficient of H+3 at two different temperatures. At 300 K 1.5×10−7 cm3 s−1 was found for ions with low degree vibrational excitation (v≤2). The ground state H+3(v=0) measured as 1.1×10−7 650 K. discussion is given states light slow deexcitation rates states. model presented.
The gas phase chemistry of neutral-neutral reactions interest in the interstellar medium (ISM) is poorly understood. rate coefficients (kOH) for majority hydroxyl (OH) radicals with oxygenated species are unknown at temperatures ISM. In this study, we present first determination kOH HC(O)OCH3 between 22.4 ± 1.4 and 64.2 1.7 K. CRESU (French acronym Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics a Uniform Supersonic Flow) technique was used to create chemical...
Combined experimental/theoretical studies demonstrate that the reaction between cyano radicals and methylamine is an efficient formation route of interstellar cyanamide.
The rate coefficient for the dissociative recombination of HCO+ has been measured using a new flowing afterglow technique which employs movable Langmuir probe to measure electron density and mass spectrometer ion density, both as function distance along flow. A value 2.2×10−7 cm3 s−1 found at 300 K. An analysis excitation state ions indicates that more than 93% are in v=0 while rest have ∼0.1 eV internal energy. discussion recent theoretical controversy concerning this is given.
The kinetics of reactions C2(a(3)Pi(u)) and C2(X(1)Sigma(g)(+)) with various hydrocarbons (CH4, C2H2, C2H4, C2H6, C3H8) have been studied in a uniform supersonic flow expansion over the temperature range 24-300 K. Rate coefficients obtained by using pulsed laser photolysis-laser induced fluorescence technique, where both radicals were produced at same time but detected separately. reactivity triplet state was found to be significantly lower than that singlet ground for all reactants whole...
The reaction between sulfur atoms in the first electronically excited state, S((1)D), and ethene (C(2)H(4)) has been investigated a complementary fashion (a) crossed-beam dynamic experiments with mass spectrometric detection time-of-flight (TOF) analysis at two collision energies (37.0 45.0 kJ mol(-1)), (b) low temperature kinetics ranging from 298 K down to 23 K, (c) electronic structure calculations of stationary points product energetics on C(2)H(4)S singlet triplet potential energy...
The kinetics of the reactions linear butadiynyl radical, C4H (CCCCH), with a variety unsaturated hydrocarbons have been studied over temperature range 39–300 K using CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme, or reaction in uniform supersonic flow) apparatus combined pulsed laser photolysis–laser induced fluorescence technique. rate coefficients for all are found to be excess 10−10 cm3 molecule−1 s−1 entire range. They can fitted following expressions (valid from 39...
A detailed description of a new pulsed supersonic uniform gas expansion system is presented together with the experimental validation setup by applying CRESU (French acronym for Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flow) technique to gas-phase reaction OH radicals 1-butene at ca. 23 K and 0.63 millibars helium (carrier gas). The carrier flow, containing negligible mixing ratios OH-precursor 1-butene, expanded from high pressure...
Gas-phase reactions in the interstellar medium (ISM) are a source of molecules this environment. The knowledge rate coefficient for neutral-neutral as function temperature, k(T), is essential to improve astrochemical models. In work, we have experimentally measured k(T) reaction between OH radical and acetaldehyde, both present many sources ISM. Laser techniques coupled CRESU system were used perform kinetic measurements. obtained modified Arrhenius equation k(T = 11.7-177.5 K) (1.2 ± 0.2) ×...