Fabrice Duvernay - Academia.edu (original) (raw)

Papers by Fabrice Duvernay

La comparaison de spectres ISO de glaces interstellaires dans la region autour de 1700cm-1 avec l... more La comparaison de spectres ISO de glaces interstellaires dans la region autour de 1700cm-1 avec le spectre obtenu en laboratoire, apres irradiation VUV de HNCO et de ses photo-produits dans la glace, conduit a des similitudes telles que nous pouvons envisager la presence de formaldehyde, de formamide (HC(O)NH2) et d'uree (NH2(CO)NH2) dans les glaces interstellaires. L'etude du comportement VUV (Vacuum Ultra-Violet) de l'uree et du formamide a basse temperature en matrice cryogenique et en phase solide permettra donc a la fois d'ameliorer les modeles de chimie interstellaire mais aussi d'ameliorer notre connaissance de la photochimie des amides qui reste jusqu'alors assez mal connue. La photolyse du formamide et de l'uree (R-CO-NH2) en matrice montre l'existence de deux voies predominantes, conduisant a la formation de HNCO + RH et CO + RNH2. Nous avons egalement mis en evidence, pour la premiere fois que ces deux amides via la transition n-π*, se deco...

We present the results of the irradiation of interstellar ice analogs (H 2 O:NH 3 :CH 3 OH) with ... more We present the results of the irradiation of interstellar ice analogs (H 2 O:NH 3 :CH 3 OH) with argon and sulfur energetic ions. The samples were generated and irradiated at 10 K, and were thick enough to ensure the projectiles were implanted in the ice, allowing the sulfur projectiles to become part of the ensuing chemistry. The samples were measured on-site with Fourier Transform Infra-Red (FT-IR) spectroscopy, and the organic residues were analyzed off-site through Very High Resolution Mass Spectrometry (VHRMS). The IR spectra did not reveal any difference between the Ar-irradiated and S-irradiated samples, but the VHRMS allowed to investigate the potential formation of sulfur-bearing organic compounds.

The Astrophysical Journal, 2015

Interstellar ices are submitted to energetic processes (thermal, UV, and cosmic-ray radiations) p... more Interstellar ices are submitted to energetic processes (thermal, UV, and cosmic-ray radiations) producing complex organic molecules. Laboratory experiments aim to reproduce the evolution of interstellar ices to better understand the chemical changes leading to the reaction, formation, and desorption of molecules. In this context, the thermal evolution of an interstellar ice analogue composed of water, carbon dioxide, ammonia, and formaldehyde is investigated. The ice evolution during the warming has been monitored by IR spectroscopy. The formation of hexamethylenetetramine (HMT) and polymethylenimine (PMI) are observed in the organic refractory residue left after ice sublimation. A better understanding of this result is realized with the study of another ice mixture containing methylenimine (a precursor of HMT) with carbon dioxide and ammonia. It appears that carbamic acid, a reaction product of carbon dioxide and ammonia, plays the role of catalyst, allowing the reactions toward HMT and PMI formation. This is the first time that such complex organic molecules (HMT, PMI) are produced from the warming (without VUV photolysis or irradiation with energetic particles) of abundant molecules observed in interstellar ices (H 2 O, NH 3 , CO 2 , H 2 CO). This result strengthens the importance of thermal reactions in the ices' evolution. HMT and PMI, likely components of interstellar ices, should be searched for in the pristine objects of our solar system, such as comets and carbonaceous chondrites.

Monthly Notices of the Royal Astronomical Society, 2015

Among all existing complex organic molecules, glycolaldehyde HOCH 2 CHO and ethylene glycol HOCH ... more Among all existing complex organic molecules, glycolaldehyde HOCH 2 CHO and ethylene glycol HOCH 2 CH 2 OH are two of the largest detected molecules in the interstellar medium. We investigate both experimentally and theoretically the low-temperature reaction pathways leading to glycolaldehyde and ethylene glycol in interstellar grains. Using infrared spectroscopy, mass spectroscopy and quantum calculations, we investigate formation pathways of glycolaldehyde and ethylene glycol based on HCO • and • CH 2 OH radical-radical recombinations. We also show that • CH 2 OH is the main intermediate radical species in the H 2 CO to CH 3 OH hydrogenation processes. We then discuss astrophysical implications of the chemical pathway we propose on the observed gas-phase ethylene glycol and glycolaldehyde.

Monthly Notices of the Royal Astronomical Society, 2015

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The thermal reactivity of a water-dominated cometary ice analog containing H 2 CO and NH 3 is inv... more The thermal reactivity of a water-dominated cometary ice analog containing H 2 CO and NH 3 is investigated by means of Fourier transform infrared spectroscopy, mass spectrometry, and B3LYP calculations. Three products are characterized by these techniques: aminomethanol (NH 2 CH 2 OH), methyleneglycol (HOCH 2 OH), and polyoxymethylene (POM, HO-(CH 2-O) n-H). Their formation strongly depends on the initial NH 3 /H 2 CO ratio. In addition, the influence of the initial ice composition on the thermal stability of POM has also been investigated. It is shown that POM formed during warming of the ices consists of short-chain polymers (i.e., oligomers of formaldehyde HO-(CH 2-O) n-H, n < 5), which are volatile at temperatures higher than 200 K. This suggests that gas-phase detection by the ROSINA instrument on board the Rosetta mission would be the most appropriate method to detect POM. Moreover, the mass spectra presented in this work might help in the interpretation of data that will be recorded by this instrument. Finally, a new scenario to explain the distributed source of formaldehyde observed in comets is discussed.

The Journal of Physical Chemistry A, 2012

We focus on low temperature reactivity from 25 to 300 K, in ice containing acetaldehyde, ammonia,... more We focus on low temperature reactivity from 25 to 300 K, in ice containing acetaldehyde, ammonia, and formic acid. We show that the warming of this ice mixture forms the acetaldehyde ammonia trimer (2,4,6-trimethyl-1,3,5-hexahydrotriazine, C(6)H(15)N(3)) after five steps. The reaction is monitored by FTIR spectroscopy and mass spectrometry. We propose a mechanism for its formation that differs from the one proposed in the liquid phase. The reaction intermediates, α-aminoethanol (from 80 K) and ethanimine (formed at 180 K), have been identified by a mechanistic approach: each step of the reaction has been treated separately. The chemical implications and the astrophysical relevance of the study are also discussed.

The Astrophysical Journal, 2009

Aminomethanol (NH 2 CH 2 OH) is formed at low temperature from the purely thermal reaction of NH ... more Aminomethanol (NH 2 CH 2 OH) is formed at low temperature from the purely thermal reaction of NH 3 and H 2 CO in laboratory interstellar ice analogs. We report for the first time its infrared and mass spectra. We study its reaction and desorption kinetics using Fourier transform infrared spectroscopy and mass spectrometry. Its reaction rate is estimated to be k(T) = 0.05 × exp(−4.5(kJ mol −1)/RT) and its desorption energy to be E des = 58 ± 2 kJ mol −1. NH 2 CH 2 OH can also contribute to the 5-8 μm region of thermally processed ices encountered in many young stellar objects. Gas phase NH 2 CH 2 OH may be present in hot core regions, when the frozen material is desorbed.

Geochimica et Cosmochimica Acta, 2013

ABSTRACT Studying the chemical composition of organic matter in astrophysical environments is an ... more ABSTRACT Studying the chemical composition of organic matter in astrophysical environments is an important means to improve our understanding of its origin and evolution. This organic matter evolves from molecular clouds to protoplanetary disks, and as a final destination, takes part in the formation of many objects of our solar system, such as primitive chondritic material, planetesimals and finally planets. In this contribution, we perform experimental simulations based on the VUV irradiation and warming-up of primitive interstellar ice analogs (CH3OH:NH3:H2O), and characterize, for the first time, the resulting refractory residue, using very high resolution mass spectrometry (VHRMS) with an LTQ-orbitrap-XL instrument. An electrospray source allows ionizing all the molecules having proton donor or acceptor chemical functions, while limiting as much as possible their damages. Thus, this method provides the analysis of the whole ionizable molecules making up the residue. The analysis of the spectra shows that these residues contain a large number of molecules formed of CHNO elements, including macromolecular entities beyond 4000 Da. The average elemental composition of the residue is of H/C = 1.5, N/C = 0.4, O/C = 0.4. These first results are tentatively compared to VHRMS analyses of the soluble organic matter (SOM) present in the Murchison’s meteorite, a primitive chondrite of the CM class. The molecular richness observed can be considered as the “first step” of the complex abiotic organic matter in extraterrestrial media. This initial matter, that may be rather universal, could then evolve toward more processed materials in parent bodies, such as comets and asteroids, materials that are then observed and subsequently analyzed in meteorites found on Earth. In addition to providing some insight on the mixture complexity, VHRMS allows for the search of specific molecules. For instance, hexamethylenetetramine (HMT) and some of its derivatives are identified in these residues. With the possibility to characterize the whole residue as well as some specific molecules, we consider that VHRMS is a powerful analytical tool for the understanding of the chemical evolution of organic matter in astrophysical environments.

Astronomy & Astrophysics, 2011

Context. The study of the chemical reactivity in interstellar ices in astrophysical environments ... more Context. The study of the chemical reactivity in interstellar ices in astrophysical environments is an important tool for understanding the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. The laboratory simulations of the reactivity in ice analogs provide important information for understanding the reactivity in these environments. Here, we used these experimental simulations to trace some formation pathways of two nitriles, acetonitrile and amino acetonitrile, which are two potential precursors of amino acids in astrophysical environments. Aims. The purpose of this work is to present the first experimental approach for the formation of acetonitrile and amino acetonitrile in interstellar-like conditions. Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy and mass spectrometry to study the formation at 20 K of acetonitrile CH 3 CN from VUV irradiation of ethylamine and of amino acetonitrile NH 2 CH 2 CN from VUV irradiation of ammonia: acetonitrile mixture. Isotopic substitutions are used to confirm identifications. Results. We demonstrate that acetonitrile can be formed at 20 K from the VUV irradiation of ethylamine with a yield of 4%. Furthermore, in presence of ammonia, at 20 K and under VUV irradiation, the acetonitrile can lead to the amino acetonitrile formation. These results suggest that acetonitrile and amino acetonitrile can be formed in astrophysical environments that are submitted to VUV irradiations.

Astronomy & Astrophysics, 2012

Context. Aminoacetonitrile (AAN) has been detected in 2008 in the hot core SgrB2. This molecule i... more Context. Aminoacetonitrile (AAN) has been detected in 2008 in the hot core SgrB2. This molecule is of particular interest because it is a central molecule in the Strecker synthesis of amino acids. This molecule can be formed from methanimine (CH 2 NH), ammonia (NH 3) and hydrogen cyanide (HCN) in astrophysical icy conditions. Nevertheless, few studies exist about its infrared (IR) identification or its astrophysical characterization. Aims. We present in this study a characterization of the pure solid AAN and when it is diluted in water to study the influence of H 2 O on the main IR features of AAN. The reactivity with CO 2 and its photoreactivity are also studied and the main products were characterized. Methods. Fourier transformed infrared (FTIR) spectroscopy of AAN molecular ice was performed in the 10-300 K temperature range. We used temperature-programmed desorption coupled with mass spectrometry detection techniques to evaluate the desorption energy value. The influence of water was studied by quantitative FTIR spectroscopy and the main reaction and photochemical products were identified by FTIR spectroscopy. Results. We determined that in our experimental conditions, the IR limit of AAN detection in the water ice is about 1 × 10 16 molecule cm −2 , which means that the AAN detection is almost impossible within the icy mantle of interstellar grains. The desorption energy of pure solid AAN is of 63.7 kJ mol −1 with ν 0 to 10 28 molecule cm −2 s −1 , which implies that the presence of this molecule in the gas phase is only possible in hot cores. The glycine (Gly) formation from the AAN through the last step of the Strecker synthesis seems to be impossible in astrophysical-like conditions. Furthermore, AAN is photoresistant to vacuum ultraviolet radiation, which emphasizes the fact that AAN can be considered as a Gly reservoir molecule.

Astronomy & Astrophysics, 2011

Context. Studing chemical reactivity in astrophysical environments is an important means for impr... more Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysicallike conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims. We present the first experimental investigation of the formation of aminoacetonitrile NH 2 CH 2 CN from the thermal processing of ices including methanimine (CH 2 NH), ammonia (NH 3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results. We demonstrate that methanimine can react with − CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH + 4 − CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH + 4 − CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH + 4 − CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

Astronomy & Astrophysics, 2011

Aims. We investigate the purely thermal formation of hexamethylenetetramine (HMT, C 6 H 12 N 4) i... more Aims. We investigate the purely thermal formation of hexamethylenetetramine (HMT, C 6 H 12 N 4) in interstellar ice analogs from nonphotolysed ice and compare our results with those for the formation from photolysed ice. Methods. We use Fourier transform-infrared spectroscopy to follow residue formation from VUV irradiation of H 2 CO:NH 3 ice mixture in different concentration ratios. We also report the warming of the H 2 CO:NH 3 :HCOOH ice mixture. Results. We present the characterization of organic residues obtained at 330 K from VUV irradiation of H 2 CO:NH 3 ice mixtures. The organic residues contain compounds related to polyoxomethylene (POM, [-CH 2-O-] n) and HMT (C 6 H 12 N 4). We report, for the first time, the formation of HMT from the warming of an interstellar ice analogs, H 2 CO:NH 3 :HCOOH, without any energetic processing (i.e. photons or particles). New insights into HMT formation mechanism are proposed. These results strengthen the hypothesis that HMT is present in interstellar grains or in comets, where it may be detected with the COSAC instrument of the Rosetta mission.

Astronomy & Astrophysics, 2013

Context. Complex organic molecules are observed in a broad variety of astrophysical objects, but ... more Context. Complex organic molecules are observed in a broad variety of astrophysical objects, but little is known about their formation mechanism. Laboratory simulations on interstellar ice analogues are therefore crucial for understanding the origin of these complex organic molecules. In this context, we focus on the thermal reactivity for the formation of the organic residue obtained after photolysis at 25 K of the interstellar ice analogue (H 2 O:CH 3 OH:NH 3) warmed to 300 K. Aims. We determine the formation mechanism of one major product detected in the organic residue: hexamethylenetetramine (HMT). We compare the warming of the photolysed interstellar ice analogue with the warming of the two non-photolysed specific ice mixtures H 2 CO:NH 3 :HCOOH and CH 2 NH:HCOOH, which are used as references. Using both general and specific approaches, we show the precise role of the UV photons and the thermal processing in the HMT formation. Methods. We used Fourier transform infrared spectroscopy (FTIR) to monitor the chemical changes induced by the heating of the photolysed ice analogue and characterize some important species that will subsequently evolve in the formation of HMT in the residue. Results. We show that the thermal processes play a key role in the HMT formation in photolysed ice analogues heated at 300 K. We identify the stable intermediates in the HMT formation that are formed during the warming: the aminomethanol (NH 2 CH 2 OH) and the protonated ion trimethyletriamine (TMTH + , C 3 H 10 N + 3). We also identify for the first time a new product in the organic residue, the polymethylenimine PMI (-(CH 2-NH) n). Results from this study will be interesting for the analysis of the forthcoming Rosetta mission.

Advances in Space Research, 2013

ABSTRACT Complex organic molecules are widely observed in star-forming regions, although their fo... more ABSTRACT Complex organic molecules are widely observed in star-forming regions, although their formation mechanisms are not well understood. Solid-state chemistry is thought to play an important role, but the solid-state reaction network is poorly known. We provide a list of purely thermal reactions involving electronically stable reactants to complement existing grain chemistry networks. The kinetic parameters of the reactions are given when available. These reactions lead to the formation of complex organic molecules, which were not considered previously. Eventually, these complex molecules are either released into the gas phase or incorporated into the organic residue found in meteorites. Thermal reactions are important because they are not limited by the UV flux or the slow diffusion of the radicals, and because they involve both surface and mantle molecules. Thermal reactions represent an important step in the formation of complex organic molecules that constitute the primitive material of comets and asteroids.

Proceedings of The International Astronomical Union, 2011

Understanding the chemistry of the interstellar medium necessitates the use of gas-grain chemistr... more Understanding the chemistry of the interstellar medium necessitates the use of gas-grain chemistry codes along with extensive databases of gas phase and solid phase reactions. If reaction rates have been measured for various types of gas phase reactions, no experimental kinetic studies are available for determining solid-state thermal reaction rates. Reactions on the grains are acknowledged to play an important

Astronomy & Astrophysics, 2013

Context. Laboratory simulations on interstellar or cometary ice analogues are crucial to understa... more Context. Laboratory simulations on interstellar or cometary ice analogues are crucial to understand the formation of complex organic molecules that are detected in the interstellar medium (ISM). Results from this work give hints on physical and chemical processes occurring in space and can serve as a benchmark for dedicated space missions. Aims. The aim of this work is to consolidate the knowledge of ice evolution during the star formation process by investigating the influence of thermal reactions as a source of molecular complexity in the ISM. In this study, we are interested in the thermal reactivity between two interstellar molecules, formaldehyde (H 2 CO) and methylamine (CH 3 NH 2) in water ice analogues. Methods. We used Fourier transform infrared spectroscopy, mass spectrometry, and B3LYP calculations to investigate the thermal reaction between formaldehyde and methylamine (14 N and 15 N) at low temperature in water ice analogues. Results. We demonstrate that methylamine and formaldehyde quickly react in water ice analogues for astronomically relevant temperatures and form N-methylaminomethanol CH 3 NHCH 2 OH. The measured activation energy of this reaction, 1.1 ± 0.05 kJ mol −1 (1.8 ± 0.08 kJ mol −1 with methylamine 15 N), allows the reaction to proceed in interstellar ices, when the ices are gently warmed, as it occurs in young stellar objects, in photo-dissociation regions, or in comets. Therefore, CH 3 NHCH 2 OH is likely to be found in these objects. This hypothesis is confirmed by numerical simulations that clearly show that the formation of N-methylaminomethanol is likely at low temperature. Isotopic experiments as well as photochemical studies have also been performed to better characterise the ice evolution induced by heat and ultraviolet radiation during star formation. Key words. astrochemistry-molecular processes-methods: laboratory-ISM: molecules Gardner & McNesby (1982) and Ogura et al. (1989) proposed its formation from the UV photolysis of a gaseous mixture containing CH 4 and NH 3. Finally, Herbst (1985) proposed a gas phase methylamine formation from the methylium cation CH + 3 and NH 3. However, solid methylamine has never been detected in ice, so far. This could be due to its low abundance, but also to the difficulty to assign this compound from ices in infrared astronomical spectra. Works on ice analogues containing methylamine suggest that a plausible cause of its nonobservation in interstellar ices is its high reactivity at low temperature (Bossa et al. 2009a). Indeed, from a chemical point of view, CH 3 NH 2 is a better nucleophile and base than ammonia. This molecule can quickly react at low temperature in interstellar ice analogues with acids, such as HNCO, HCN, and HCOOH. In addition, methylamine reacts at low temperature with CO 2 , leading to the formation of methylammonium methylcarbamate (CH 3 NH + 3 CH 3 NHCOO −), which can be isomerised into glycine under UV irradiation (Bossa et al. 2009a). The measured activation barrier for this latter reaction, 3.7 kJ mol −1 , is compatible with low temperature observed in molecular clouds Article published by EDP Sciences

La comparaison de spectres ISO de glaces interstellaires dans la region autour de 1700cm-1 avec l... more La comparaison de spectres ISO de glaces interstellaires dans la region autour de 1700cm-1 avec le spectre obtenu en laboratoire, apres irradiation VUV de HNCO et de ses photo-produits dans la glace, conduit a des similitudes telles que nous pouvons envisager la presence de formaldehyde, de formamide (HC(O)NH2) et d'uree (NH2(CO)NH2) dans les glaces interstellaires. L'etude du comportement VUV (Vacuum Ultra-Violet) de l'uree et du formamide a basse temperature en matrice cryogenique et en phase solide permettra donc a la fois d'ameliorer les modeles de chimie interstellaire mais aussi d'ameliorer notre connaissance de la photochimie des amides qui reste jusqu'alors assez mal connue. La photolyse du formamide et de l'uree (R-CO-NH2) en matrice montre l'existence de deux voies predominantes, conduisant a la formation de HNCO + RH et CO + RNH2. Nous avons egalement mis en evidence, pour la premiere fois que ces deux amides via la transition n-π*, se deco...

We present the results of the irradiation of interstellar ice analogs (H 2 O:NH 3 :CH 3 OH) with ... more We present the results of the irradiation of interstellar ice analogs (H 2 O:NH 3 :CH 3 OH) with argon and sulfur energetic ions. The samples were generated and irradiated at 10 K, and were thick enough to ensure the projectiles were implanted in the ice, allowing the sulfur projectiles to become part of the ensuing chemistry. The samples were measured on-site with Fourier Transform Infra-Red (FT-IR) spectroscopy, and the organic residues were analyzed off-site through Very High Resolution Mass Spectrometry (VHRMS). The IR spectra did not reveal any difference between the Ar-irradiated and S-irradiated samples, but the VHRMS allowed to investigate the potential formation of sulfur-bearing organic compounds.

The Astrophysical Journal, 2015

Interstellar ices are submitted to energetic processes (thermal, UV, and cosmic-ray radiations) p... more Interstellar ices are submitted to energetic processes (thermal, UV, and cosmic-ray radiations) producing complex organic molecules. Laboratory experiments aim to reproduce the evolution of interstellar ices to better understand the chemical changes leading to the reaction, formation, and desorption of molecules. In this context, the thermal evolution of an interstellar ice analogue composed of water, carbon dioxide, ammonia, and formaldehyde is investigated. The ice evolution during the warming has been monitored by IR spectroscopy. The formation of hexamethylenetetramine (HMT) and polymethylenimine (PMI) are observed in the organic refractory residue left after ice sublimation. A better understanding of this result is realized with the study of another ice mixture containing methylenimine (a precursor of HMT) with carbon dioxide and ammonia. It appears that carbamic acid, a reaction product of carbon dioxide and ammonia, plays the role of catalyst, allowing the reactions toward HMT and PMI formation. This is the first time that such complex organic molecules (HMT, PMI) are produced from the warming (without VUV photolysis or irradiation with energetic particles) of abundant molecules observed in interstellar ices (H 2 O, NH 3 , CO 2 , H 2 CO). This result strengthens the importance of thermal reactions in the ices' evolution. HMT and PMI, likely components of interstellar ices, should be searched for in the pristine objects of our solar system, such as comets and carbonaceous chondrites.

Monthly Notices of the Royal Astronomical Society, 2015

Among all existing complex organic molecules, glycolaldehyde HOCH 2 CHO and ethylene glycol HOCH ... more Among all existing complex organic molecules, glycolaldehyde HOCH 2 CHO and ethylene glycol HOCH 2 CH 2 OH are two of the largest detected molecules in the interstellar medium. We investigate both experimentally and theoretically the low-temperature reaction pathways leading to glycolaldehyde and ethylene glycol in interstellar grains. Using infrared spectroscopy, mass spectroscopy and quantum calculations, we investigate formation pathways of glycolaldehyde and ethylene glycol based on HCO • and • CH 2 OH radical-radical recombinations. We also show that • CH 2 OH is the main intermediate radical species in the H 2 CO to CH 3 OH hydrogenation processes. We then discuss astrophysical implications of the chemical pathway we propose on the observed gas-phase ethylene glycol and glycolaldehyde.

Monthly Notices of the Royal Astronomical Society, 2015

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The thermal reactivity of a water-dominated cometary ice analog containing H 2 CO and NH 3 is inv... more The thermal reactivity of a water-dominated cometary ice analog containing H 2 CO and NH 3 is investigated by means of Fourier transform infrared spectroscopy, mass spectrometry, and B3LYP calculations. Three products are characterized by these techniques: aminomethanol (NH 2 CH 2 OH), methyleneglycol (HOCH 2 OH), and polyoxymethylene (POM, HO-(CH 2-O) n-H). Their formation strongly depends on the initial NH 3 /H 2 CO ratio. In addition, the influence of the initial ice composition on the thermal stability of POM has also been investigated. It is shown that POM formed during warming of the ices consists of short-chain polymers (i.e., oligomers of formaldehyde HO-(CH 2-O) n-H, n < 5), which are volatile at temperatures higher than 200 K. This suggests that gas-phase detection by the ROSINA instrument on board the Rosetta mission would be the most appropriate method to detect POM. Moreover, the mass spectra presented in this work might help in the interpretation of data that will be recorded by this instrument. Finally, a new scenario to explain the distributed source of formaldehyde observed in comets is discussed.

The Journal of Physical Chemistry A, 2012

We focus on low temperature reactivity from 25 to 300 K, in ice containing acetaldehyde, ammonia,... more We focus on low temperature reactivity from 25 to 300 K, in ice containing acetaldehyde, ammonia, and formic acid. We show that the warming of this ice mixture forms the acetaldehyde ammonia trimer (2,4,6-trimethyl-1,3,5-hexahydrotriazine, C(6)H(15)N(3)) after five steps. The reaction is monitored by FTIR spectroscopy and mass spectrometry. We propose a mechanism for its formation that differs from the one proposed in the liquid phase. The reaction intermediates, α-aminoethanol (from 80 K) and ethanimine (formed at 180 K), have been identified by a mechanistic approach: each step of the reaction has been treated separately. The chemical implications and the astrophysical relevance of the study are also discussed.

The Astrophysical Journal, 2009

Aminomethanol (NH 2 CH 2 OH) is formed at low temperature from the purely thermal reaction of NH ... more Aminomethanol (NH 2 CH 2 OH) is formed at low temperature from the purely thermal reaction of NH 3 and H 2 CO in laboratory interstellar ice analogs. We report for the first time its infrared and mass spectra. We study its reaction and desorption kinetics using Fourier transform infrared spectroscopy and mass spectrometry. Its reaction rate is estimated to be k(T) = 0.05 × exp(−4.5(kJ mol −1)/RT) and its desorption energy to be E des = 58 ± 2 kJ mol −1. NH 2 CH 2 OH can also contribute to the 5-8 μm region of thermally processed ices encountered in many young stellar objects. Gas phase NH 2 CH 2 OH may be present in hot core regions, when the frozen material is desorbed.

Geochimica et Cosmochimica Acta, 2013

ABSTRACT Studying the chemical composition of organic matter in astrophysical environments is an ... more ABSTRACT Studying the chemical composition of organic matter in astrophysical environments is an important means to improve our understanding of its origin and evolution. This organic matter evolves from molecular clouds to protoplanetary disks, and as a final destination, takes part in the formation of many objects of our solar system, such as primitive chondritic material, planetesimals and finally planets. In this contribution, we perform experimental simulations based on the VUV irradiation and warming-up of primitive interstellar ice analogs (CH3OH:NH3:H2O), and characterize, for the first time, the resulting refractory residue, using very high resolution mass spectrometry (VHRMS) with an LTQ-orbitrap-XL instrument. An electrospray source allows ionizing all the molecules having proton donor or acceptor chemical functions, while limiting as much as possible their damages. Thus, this method provides the analysis of the whole ionizable molecules making up the residue. The analysis of the spectra shows that these residues contain a large number of molecules formed of CHNO elements, including macromolecular entities beyond 4000 Da. The average elemental composition of the residue is of H/C = 1.5, N/C = 0.4, O/C = 0.4. These first results are tentatively compared to VHRMS analyses of the soluble organic matter (SOM) present in the Murchison’s meteorite, a primitive chondrite of the CM class. The molecular richness observed can be considered as the “first step” of the complex abiotic organic matter in extraterrestrial media. This initial matter, that may be rather universal, could then evolve toward more processed materials in parent bodies, such as comets and asteroids, materials that are then observed and subsequently analyzed in meteorites found on Earth. In addition to providing some insight on the mixture complexity, VHRMS allows for the search of specific molecules. For instance, hexamethylenetetramine (HMT) and some of its derivatives are identified in these residues. With the possibility to characterize the whole residue as well as some specific molecules, we consider that VHRMS is a powerful analytical tool for the understanding of the chemical evolution of organic matter in astrophysical environments.

Astronomy & Astrophysics, 2011

Context. The study of the chemical reactivity in interstellar ices in astrophysical environments ... more Context. The study of the chemical reactivity in interstellar ices in astrophysical environments is an important tool for understanding the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. The laboratory simulations of the reactivity in ice analogs provide important information for understanding the reactivity in these environments. Here, we used these experimental simulations to trace some formation pathways of two nitriles, acetonitrile and amino acetonitrile, which are two potential precursors of amino acids in astrophysical environments. Aims. The purpose of this work is to present the first experimental approach for the formation of acetonitrile and amino acetonitrile in interstellar-like conditions. Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy and mass spectrometry to study the formation at 20 K of acetonitrile CH 3 CN from VUV irradiation of ethylamine and of amino acetonitrile NH 2 CH 2 CN from VUV irradiation of ammonia: acetonitrile mixture. Isotopic substitutions are used to confirm identifications. Results. We demonstrate that acetonitrile can be formed at 20 K from the VUV irradiation of ethylamine with a yield of 4%. Furthermore, in presence of ammonia, at 20 K and under VUV irradiation, the acetonitrile can lead to the amino acetonitrile formation. These results suggest that acetonitrile and amino acetonitrile can be formed in astrophysical environments that are submitted to VUV irradiations.

Astronomy & Astrophysics, 2012

Context. Aminoacetonitrile (AAN) has been detected in 2008 in the hot core SgrB2. This molecule i... more Context. Aminoacetonitrile (AAN) has been detected in 2008 in the hot core SgrB2. This molecule is of particular interest because it is a central molecule in the Strecker synthesis of amino acids. This molecule can be formed from methanimine (CH 2 NH), ammonia (NH 3) and hydrogen cyanide (HCN) in astrophysical icy conditions. Nevertheless, few studies exist about its infrared (IR) identification or its astrophysical characterization. Aims. We present in this study a characterization of the pure solid AAN and when it is diluted in water to study the influence of H 2 O on the main IR features of AAN. The reactivity with CO 2 and its photoreactivity are also studied and the main products were characterized. Methods. Fourier transformed infrared (FTIR) spectroscopy of AAN molecular ice was performed in the 10-300 K temperature range. We used temperature-programmed desorption coupled with mass spectrometry detection techniques to evaluate the desorption energy value. The influence of water was studied by quantitative FTIR spectroscopy and the main reaction and photochemical products were identified by FTIR spectroscopy. Results. We determined that in our experimental conditions, the IR limit of AAN detection in the water ice is about 1 × 10 16 molecule cm −2 , which means that the AAN detection is almost impossible within the icy mantle of interstellar grains. The desorption energy of pure solid AAN is of 63.7 kJ mol −1 with ν 0 to 10 28 molecule cm −2 s −1 , which implies that the presence of this molecule in the gas phase is only possible in hot cores. The glycine (Gly) formation from the AAN through the last step of the Strecker synthesis seems to be impossible in astrophysical-like conditions. Furthermore, AAN is photoresistant to vacuum ultraviolet radiation, which emphasizes the fact that AAN can be considered as a Gly reservoir molecule.

Astronomy & Astrophysics, 2011

Context. Studing chemical reactivity in astrophysical environments is an important means for impr... more Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysicallike conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims. We present the first experimental investigation of the formation of aminoacetonitrile NH 2 CH 2 CN from the thermal processing of ices including methanimine (CH 2 NH), ammonia (NH 3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results. We demonstrate that methanimine can react with − CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH + 4 − CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH + 4 − CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH + 4 − CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

Astronomy & Astrophysics, 2011

Aims. We investigate the purely thermal formation of hexamethylenetetramine (HMT, C 6 H 12 N 4) i... more Aims. We investigate the purely thermal formation of hexamethylenetetramine (HMT, C 6 H 12 N 4) in interstellar ice analogs from nonphotolysed ice and compare our results with those for the formation from photolysed ice. Methods. We use Fourier transform-infrared spectroscopy to follow residue formation from VUV irradiation of H 2 CO:NH 3 ice mixture in different concentration ratios. We also report the warming of the H 2 CO:NH 3 :HCOOH ice mixture. Results. We present the characterization of organic residues obtained at 330 K from VUV irradiation of H 2 CO:NH 3 ice mixtures. The organic residues contain compounds related to polyoxomethylene (POM, [-CH 2-O-] n) and HMT (C 6 H 12 N 4). We report, for the first time, the formation of HMT from the warming of an interstellar ice analogs, H 2 CO:NH 3 :HCOOH, without any energetic processing (i.e. photons or particles). New insights into HMT formation mechanism are proposed. These results strengthen the hypothesis that HMT is present in interstellar grains or in comets, where it may be detected with the COSAC instrument of the Rosetta mission.

Astronomy & Astrophysics, 2013

Context. Complex organic molecules are observed in a broad variety of astrophysical objects, but ... more Context. Complex organic molecules are observed in a broad variety of astrophysical objects, but little is known about their formation mechanism. Laboratory simulations on interstellar ice analogues are therefore crucial for understanding the origin of these complex organic molecules. In this context, we focus on the thermal reactivity for the formation of the organic residue obtained after photolysis at 25 K of the interstellar ice analogue (H 2 O:CH 3 OH:NH 3) warmed to 300 K. Aims. We determine the formation mechanism of one major product detected in the organic residue: hexamethylenetetramine (HMT). We compare the warming of the photolysed interstellar ice analogue with the warming of the two non-photolysed specific ice mixtures H 2 CO:NH 3 :HCOOH and CH 2 NH:HCOOH, which are used as references. Using both general and specific approaches, we show the precise role of the UV photons and the thermal processing in the HMT formation. Methods. We used Fourier transform infrared spectroscopy (FTIR) to monitor the chemical changes induced by the heating of the photolysed ice analogue and characterize some important species that will subsequently evolve in the formation of HMT in the residue. Results. We show that the thermal processes play a key role in the HMT formation in photolysed ice analogues heated at 300 K. We identify the stable intermediates in the HMT formation that are formed during the warming: the aminomethanol (NH 2 CH 2 OH) and the protonated ion trimethyletriamine (TMTH + , C 3 H 10 N + 3). We also identify for the first time a new product in the organic residue, the polymethylenimine PMI (-(CH 2-NH) n). Results from this study will be interesting for the analysis of the forthcoming Rosetta mission.

Advances in Space Research, 2013

ABSTRACT Complex organic molecules are widely observed in star-forming regions, although their fo... more ABSTRACT Complex organic molecules are widely observed in star-forming regions, although their formation mechanisms are not well understood. Solid-state chemistry is thought to play an important role, but the solid-state reaction network is poorly known. We provide a list of purely thermal reactions involving electronically stable reactants to complement existing grain chemistry networks. The kinetic parameters of the reactions are given when available. These reactions lead to the formation of complex organic molecules, which were not considered previously. Eventually, these complex molecules are either released into the gas phase or incorporated into the organic residue found in meteorites. Thermal reactions are important because they are not limited by the UV flux or the slow diffusion of the radicals, and because they involve both surface and mantle molecules. Thermal reactions represent an important step in the formation of complex organic molecules that constitute the primitive material of comets and asteroids.

Proceedings of The International Astronomical Union, 2011

Understanding the chemistry of the interstellar medium necessitates the use of gas-grain chemistr... more Understanding the chemistry of the interstellar medium necessitates the use of gas-grain chemistry codes along with extensive databases of gas phase and solid phase reactions. If reaction rates have been measured for various types of gas phase reactions, no experimental kinetic studies are available for determining solid-state thermal reaction rates. Reactions on the grains are acknowledged to play an important

Astronomy & Astrophysics, 2013

Context. Laboratory simulations on interstellar or cometary ice analogues are crucial to understa... more Context. Laboratory simulations on interstellar or cometary ice analogues are crucial to understand the formation of complex organic molecules that are detected in the interstellar medium (ISM). Results from this work give hints on physical and chemical processes occurring in space and can serve as a benchmark for dedicated space missions. Aims. The aim of this work is to consolidate the knowledge of ice evolution during the star formation process by investigating the influence of thermal reactions as a source of molecular complexity in the ISM. In this study, we are interested in the thermal reactivity between two interstellar molecules, formaldehyde (H 2 CO) and methylamine (CH 3 NH 2) in water ice analogues. Methods. We used Fourier transform infrared spectroscopy, mass spectrometry, and B3LYP calculations to investigate the thermal reaction between formaldehyde and methylamine (14 N and 15 N) at low temperature in water ice analogues. Results. We demonstrate that methylamine and formaldehyde quickly react in water ice analogues for astronomically relevant temperatures and form N-methylaminomethanol CH 3 NHCH 2 OH. The measured activation energy of this reaction, 1.1 ± 0.05 kJ mol −1 (1.8 ± 0.08 kJ mol −1 with methylamine 15 N), allows the reaction to proceed in interstellar ices, when the ices are gently warmed, as it occurs in young stellar objects, in photo-dissociation regions, or in comets. Therefore, CH 3 NHCH 2 OH is likely to be found in these objects. This hypothesis is confirmed by numerical simulations that clearly show that the formation of N-methylaminomethanol is likely at low temperature. Isotopic experiments as well as photochemical studies have also been performed to better characterise the ice evolution induced by heat and ultraviolet radiation during star formation. Key words. astrochemistry-molecular processes-methods: laboratory-ISM: molecules Gardner & McNesby (1982) and Ogura et al. (1989) proposed its formation from the UV photolysis of a gaseous mixture containing CH 4 and NH 3. Finally, Herbst (1985) proposed a gas phase methylamine formation from the methylium cation CH + 3 and NH 3. However, solid methylamine has never been detected in ice, so far. This could be due to its low abundance, but also to the difficulty to assign this compound from ices in infrared astronomical spectra. Works on ice analogues containing methylamine suggest that a plausible cause of its nonobservation in interstellar ices is its high reactivity at low temperature (Bossa et al. 2009a). Indeed, from a chemical point of view, CH 3 NH 2 is a better nucleophile and base than ammonia. This molecule can quickly react at low temperature in interstellar ice analogues with acids, such as HNCO, HCN, and HCOOH. In addition, methylamine reacts at low temperature with CO 2 , leading to the formation of methylammonium methylcarbamate (CH 3 NH + 3 CH 3 NHCOO −), which can be isomerised into glycine under UV irradiation (Bossa et al. 2009a). The measured activation barrier for this latter reaction, 3.7 kJ mol −1 , is compatible with low temperature observed in molecular clouds Article published by EDP Sciences