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Jean-Christophe Loison

Jean-Christophe Loison
CNRS - Bordeaux

CNRS

About

227
Publications
21,165
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Introduction
I am currently a research director at the CNRS (Bordeaux). I work on the photoionization of radicals and on the construction of chemical networks for astrochemistry and planetology.
Additional affiliations
September 2015 - December 2015
Institut des Sciences Moléculaires
Position
  • Research Director
October 1995 - present
Université Bordeaux 1
Position
  • Research Director

Publications

Publications (227)
Preprint
Full-text available
The molecule studied in this work, 2-hydroxyprop-2-enal, is among the candidates to be searched for in the interstellar medium (ISM), as it is a dehydration product of C3 sugars and contains structural motifs typical for some interstellar molecules. The aim of this work is to deepen knowledge about the millimetre-wave spectrum of 2-hydroxyprop-2-en...
Data
3 files are available: - Supplementary_Atm_species: contains the list of all the species and all the reactions used in our chemical scheme. - Supplementary_Key_chem_react: contains tables displaying key chemical reactions for the main species of Triton's atmosphere. Reaction rates of these reactions are also plotted. -Supplementary_Key_uncert_r...
Presentation
Full-text available
This paper has been written in preparation of an ISSI workshop dedicated to the habitability of Titan's subsurface water ocean (Bern, August 21-26, 2022). We present some results concerning the contribution of photochemical models to the knowledge of the various compounds (including organic molecules and aerosols) that could interact with the surfa...
Presentation
Full-text available
In the present working paper, we show some results, obtained with our up-to-date 1D photochemical model, about the photochemical production of H2 and CO in the atmosphere of Titan as a function of time. Beginning with an atmosphere composed of only N2 , Ar and CH4 (with boundary conditions kept constant with time), we find that about 15 billions of...
Preprint
Atomic oxygen in its first excited singlet state, O(1 D), is an important species in the photochemistry of several planetary atmospheres and has been predicted to be a potentially important reactive species on interstellar ices. Here, we report the results of a kinetic study of the reactions of O(1 D) with methanol, CH3OH, and acetonitrile, CH3CN,...
Presentation
Full-text available
In a recent paper, Carrasco et al. 2022 detected two new diazo-ions in an experiment that mimics photochemical processes in Titan's atmosphere. We present original results about the impact of a new species (CH2N2+) on the photochemistry of Titan's atmosphere using our up-to-date 1D-photochemical model.
Article
The (sub-)millimeter wave spectrum of the non-rigid CH 2 OH radical is investigated both experimentally and theoretically. Ab initio calculations are carried out to quantitatively characterize its potential energy surface as a function of the two large amplitude ∠H 1 COH and ∠H 2 COH dihedral angles. It is shown that the radical displays a large am...
Presentation
Full-text available
We have built a new chemical scheme to predict the abundance of HNCO and HCNO in the atmosphere of Titan as a function of altitude from a 1D photochemical model coupling neutrals and ions. The altitude profiles of the two isomers are slightly different. HNCO is more abundant in the ionosphere and HCNO is more abundant in the stratosphere. A first s...
Article
The first measurement of the photoelectron spectrum of the silylidyne free radical, SiH, is reported between 7and 10.5 eV. Two main photoionizing transitions involving the neutral ground state, X ⁺ ¹ Σ ⁺ ← X ² Π, and a ⁺ ³ Π← X ² Π, are assigned using ab initio calculations. The corresponding adiabatic ionization energies are derived,IE ad (X ⁺ ¹ Σ...
Article
Atomic oxygen in its first excited singlet state, O(1D), is an important species in the photochemistry of several planetary atmospheres and has been predicted to be a potentially important reactive species on interstellar ices. Here, we report the results of a kinetic study of the reactions of O(1D) with methanol, CH3OH, and acetonitrile, CH3CN, ov...
Article
Full-text available
We report the mass-selected slow photoelectron spectra of three reactive organophosphorus species, PCH2, and the two isomers, methylenephosphine or phosphaethylene, HPCH2 and methylphosphinidine, P-CH3. All spectra were recorded by double imaging photoelectron-photoion coincidence spectroscopy (i2PEPICO) using synchrotron radiation and all specie...
Preprint
Full-text available
Characterizing the molecular composition of solar-type protostars is useful for improving our understanding of the physico-chemical conditions under which the Sun and its planets formed. In this work, we analyzed the Atacama Large Millimeter/submillimeter Array (ALMA) data of the Protostellar Interferometric Line Survey (PILS), an unbiased spectral...
Article
Full-text available
Characterizing the molecular composition of solar-type protostars is useful for improving our understanding of the physico-chemical conditions under which the Sun and its planets formed. In this work, we analyzed the Atacama Large Millimeter/submillimeter Array (ALMA) data of the Protostellar Interferometric Line Survey (PILS), an unbiased spectral...
Preprint
Full-text available
The reaction between atomic carbon in its ground electronic state, C(3P), and nitrous oxide, N2O, has been studied below room temperature due to its potential importance for astrochemistry, with both species considered to be present at high abundance levels in a range of interstellar environments. On the experimental side, we measured rate constant...
Article
Full-text available
VUV photoionization dynamics of the S2 molecule were re-investigated from threshold up to 15.0 eV, using synchrotron radiation coupled with double imaging photoelectron/photoion coincidence featuring high resolution capabilities. We measured the first threshold photoelectron spectrum of S2 achieving higher resolution than previous literature to der...
Preprint
Full-text available
Under cold conditions in dense cores, gas-phase molecules and atoms are depleted from the gas-phase to the surface of interstellar grains. Considering the time scales and physical conditions within these cores, a portion of these molecules has to be brought back into the gas-phase to explain their observation by milimeter telescopes. We tested the...
Article
Full-text available
Context. Under cold conditions in dense cores, gas-phase molecules and atoms are depleted from the gas-phase to the surface of interstellar grains. Considering the time scales and physical conditions within these cores, a portion of these molecules has to be brought back into the gas-phase to explain their observation by milimeter telescopes. Aims....
Conference Paper
Full-text available
Determination of accurate ionization and appearance energies are always crucial for any reactive intermediate as it permits to derive accurate binding energies and standard heats of formation. Moreover, photoelectron spectra (PES) give valuable information regarding the nature of bonding, threshold for dissociative photoionization and cationic stru...
Article
Full-text available
Observational data of Titan's atmosphere composition, gathered in particular by the Cassini mission, allow accessing latitudinal, longitudinal and temporal variations of the altitudinal profiles of several species. While 1D models are a powerful tool to gain insight into the chemistry occurring in Titan's atmosphere, they cannot capture the four-di...
Article
Full-text available
The NH2 radical is a key component in many astrophysical environments, both in its neutral and cationic forms, being involved in the formation of complex N-bearing species. To gain insight into the photochemical processes into which it operates and to model accurately the ensuing chemical networks, the knowledge of its photoionization efficiency is...
Preprint
Full-text available
Rate constants have been measured for the C(3P) + CH3CN reaction between 50 K and 296 K using a continuous-flow supersonic reactor. C(3P) atoms were created by the in-situ pulsed laser photolysis of CBr4 at 266 nm, while the kinetics of C(3P) atom loss were followed by direct vacuum ultra-violet laser induced fluorescence at 115.8 nm. Secondary mea...
Preprint
Full-text available
Aims: Interstellar molecules form early in the evolutionary sequence of interstellar material that eventually forms stars and planets. To understand this evolutionary sequence, it is important to characterize the chemical composition of its first steps. Methods: In this paper, we present the result of a 2 and 3 mm survey of five cold clumps identif...
Preprint
Full-text available
Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30m Large Program designed to estimate the S, C, N, and O depletions and gas ionization degree, X(e-), in a set of star-forming filaments of Taurus, Perseus and Orion. Our immediate goal is to build up a complete database of molecular abundances that can serve as an observational...
Article
Full-text available
Aims. Interstellar molecules form early in the evolutionary sequence of interstellar material that eventually forms stars and planets. To understand this evolutionary sequence, it is important to characterize the chemical composition of its first steps. Methods. In this paper, we present the result of a 2 and 3 mm survey of five cold clumps identif...
Presentation
Full-text available
The chemistry that occurs in the ionosphere of Titan is very active. Ionospheric composition is mainly driven by coupled ion-neutral chemistry and molecular diffusion. Although ion diffusion and ion escape are expected to occur, these processes are not usually included in pho-tochemical models. In the present study, we introduce ambipolar diffusion...
Article
Context. Carbon monosulphide (CS) is among the most abundant gas-phase S-bearing molecules in cold dark molecular clouds. It is easily observable with several transitions in the millimeter wavelength range, and has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. However, chemical model...
Preprint
Full-text available
CS is among the most abundant gas-phase S-bearing molecules in cold dark molecular clouds. It is easily observable with several transitions in the millimeter wavelength range, and has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. Chemical models fail to account for the observed CS ab...
Article
The rates of numerous activated reactions between neutral species increase at low temperatures through quantum mechanical tunneling of light hydrogen atoms. Although tunneling processes involving molecules or heavy atoms are well known in the condensed phase, analogous gas-phase processes have never been demonstrated experimentally. Here, we studie...
Preprint
Full-text available
Nitrogen-bearing molecules display variable isotopic fractionation levels in different astronomical environments such as in the interstellar medium or in the Solar System. Models of interstellar chemistry are unable to induce nitrogen fraction in cold molecular clouds as exchange reactions for 15N are mostly inefficient. Here, we developed a new ga...
Preprint
Full-text available
The rates of numerous activated reactions between neutral species increase at low temperatures through quantum mechanical tunneling of light hydrogen atoms. Although tunneling processes involving molecules or heavy atoms are well known in the condensed phase, analogous gas-phase processes have never been demonstrated experimentally. Here, we studie...
Article
The two isomers of propylperoxy radical 1-C 3 H 7 O 2 and 2-C 3 H 7 O 2 , together with their rotamers, are individually identified and assigned.
Preprint
Full-text available
Neptune remains a mysterious world that deserves further exploration and is a high-priority objective for a future planetary mission in order to better understand the formation and evolution of ice giant planets. We have developed a coupled ion-neutral 1D photochemical model of Neptune's atmosphere to study the origin and evolution of the hydrocarb...
Preprint
Full-text available
Electronically excited nitrogen atoms N(2D) are important species in the photochemistry of N2 based planetary atmospheres such as Titan. Despite this, few N(2D) reactions have been studied over the appropriate low temperature range. During the present work, rate constants were measured for the N(2D) + ethene (C2H4) reaction using a supersonic flow...
Article
Full-text available
Context. The hydroxymethyl radical (CH 2 OH) is one of two structural isomers, together with the methoxy radical (CH 3 O), that can be produced by abstraction of a hydrogen atom from methanol (CH 3 OH). In the interstellar medium (ISM), both CH 2 OH and CH 3 O are suspected to be intermediate species in many chemical reactions, including those of f...
Article
We present a combined experimental and theoretical study of the threshold photoelectron spectroscopy of the vinyl radical encompassing the first triplet excited state of the vinyl cation. The radicals were produced in a flow-tube reactor by hydrogen abstraction of C2H4 and CH4 using fluorine atoms generated in a microwave discharge. Vinyl was ionis...
Article
We report a synchrotron radiation vacuum ultraviolet photoionization study of the hydroperoxyl radical (HO2), a key reaction intermediatein combustion and atmospheric chemistry as well as astrochemistry, using double imaging photoelectron photoion coincidence spectroscopy.The HO2radical is formed in a microwave discharge flow tube reactor through a...
Article
Carbon containing molecules in cold molecular clouds show various levels of isotopic fractionation through multiple observations. To understand such effects, we have developed a new gas-grain chemical model with updated 13C fractionation reactions (also including the corresponding reactions for 15 N, 18O, and 34S). For chemical ages typical of dens...
Preprint
Full-text available
Measuring isotopic ratios is a sensitive technique used to obtain information on stellar nucleosynthesis and chemical evolution. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50km/s Cloud and several l.o.s. clouds towards Sgr B2(N). Towards...
Article
Full-text available
Context. Measuring isotopic ratios is a sensitive technique used to obtain information on stellar nucleosynthesis and chemical evolution. Aims. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50 km s ⁻¹ Cloud and several line-of-sight clouds t...
Preprint
Full-text available
Carbon containing molecules in cold molecular clouds show various levels of isotopic fractionation through multiple observations. To understand such effects, we have developed a new gas-grain chemical model with updated 13C fractionation reactions (also including the corresponding reactions for 15N, 18O and 34S). For chemical ages typical of dense...
Article
The vacuum-ultraviolet threshold photoelectron spectrum of methyl isocyanate CH3NCO has been recorded from 10.4 eV to 12 eV using synchrotron radiation and a coincidence technique allowing for a mass-discrimination of the photoelectron signal. A significant improvement is achieved over previous investigations as this experimental setup leads to a m...
Article
We present here a synchrotron radiation vacuum ultraviolet photoionization study of the simplest alkoxy radical, CH3O, a key reaction intermediate in atmospheric and combustion chemistry. A microwave discharge fast flow tube connected to a molecular beam sampling system is employed as a chemical reactor to initiate reactions and generate radicals....
Article
Context. Complex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (C 2 H 3 CHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. Aims. This study aims to search for the presence of C 2 H 3 CHO and other three-carbo...
Article
Full-text available
Context. Complex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (C 2 H 3 CHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. Aims. This study aims to search for the presence of C 2 H 3 CHO and other three-carbo...
Preprint
Complex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (C$_2$H$_3$CHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. This study aims to search for the presence of C$_2$H$_3$CHO and other three-carbon species s...