Infrared and Reflectron Time-of-Flight Mass Spectroscopic Study on the Synthesis of Glycolaldehyde in Methanol (CH3OH) and Methanol-Carbon Monoxide (CH3OH-CO) Ices Exposed to Ionization Radiation (original) (raw)
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Astrophysical Journal, 2007
Binary mixtures of methanol (CH 3 OH ) and carbon monoxide (CO) ices were irradiated at 10 K with energetic electrons to mimic the energy transfer processes that occur in the track of the trajectories of MeV cosmic-ray particles. The formation of glycolaldehyde (HCOCH 2 OH) was established through the appearance of new bands in the infrared spectrum at 1757, 1700, 1690, 1367, 1267, and 1067 cm À1 . A second C 2 H 4 O 2 isomer, methyl formate (HCOOCH 3 ), was also identified by absorptions appearing at 1718, 1159, and 914 cm À1 . Mass spectrometer signals during the warm-up of the ice sample showed sublimation of both the glycolaldehyde and methyl formate; these species were monitored via the C 2 H 4 O 2 + molecular ion at mass-to-charge ratio, m/e, of 60 originating from both glycolaldehyde and the methyl formate isomer. The latter was distinguishable by the presence of a second signal at m/e = 45, i.e., the HCO 2 + ion. Kinetic fits of the column densities of the reactants and products suggest the initial step of the formation process is the cleavage of a CÀH bond in the methanol molecule to generate either the hydroxymethyl (CH 2 OH) or methoxy (CH 3 O) radical plus atomic hydrogen. The hydrogen atom holds excess kinetic energy, allowing it to overcome entrance barriers required; therefore, a hydrogen could add to a CO molecule, generating the formyl radical (HCO). This can recombine with the hydroxymethyl radical to form glycolaldehyde or with the methoxy radical to yield methyl formate. Similar processes are expected to form glycolaldehyde and methyl formate in the interstellar medium on grains and possibly on cometary ices, thus providing alternatives to gas-phase processes for the generation of complex species whose fractional abundances compared with H 2 of typically a few times 10 À9 cannot be accounted for solely by gas-phase chemistry.
Monthly Notices of the Royal Astronomical Society, 2015
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.
Mechanistical Studies on the Irradiation of Methanol in Extraterrestrial Ices
Astrophysical Journal, 2007
Pure ices of amorphous methanol, CH 3 OH(X 1 A 0 ), were irradiated at 11 K by 5 keV electrons at 100 nA for 1 hr. These energetic electrons simulate electronic energy transfer processes that occur as interstellar ices, comets, and icy solar system bodies are subjected to irradiation from MeV ions and secondary electrons produced in this process. The results were analyzed quantitatively via absorption-reflection-absorption Fourier transform infrared ( FTIR) spectroscopy, with the identification of new species aided by high-level electronic structure calculations. The unimolecular decomposition of methanol was found to proceed via the formation of (1) the hydroxymethyl radical, CH 2 OH(X 2 A 00 ), and atomic hydrogen, H( 2 S 1=2 ), (2) the methoxy radical, CH 3 O(X 2 A 0 ), plus atomic hydrogen, (3) formaldehyde, H 2 CO(X 1 A 1 ) plus molecular hydrogen, H 2 (X 1 AE þ g ), and (4) the formation of methane, CH 4 (X 1 A 1 ), together with atomic oxygen, O( 1 D). The accessibility of the last channel indicates that the reverse process, oxygen addition into methane to form methanol, should also be feasible. A kinetic model is presented for the decomposition of methanol into these species, as well as the formyl radical, HCO(X 2 A 0 ), and carbon monoxide, CO(X 1 AE þ ). During the subsequent warming up of the sample, radicals previously generated within the matrix were mobilized and found to recombine to form methyl formate, CH 3 OCHO(X 1 A 0 ), glycolaldehyde, CH 2 OHCHO(X 1 A 0 ), and ethylene glycol, HOCH 2 CH 2 OH(X 1 A). Upper limits for the production of these species by the recombination of neighboring radicals produced during irradiation as well as during the warm-up procedure are presented. The generation of these molecules by irradiation of ices in the solid state and their subsequent sublimation into the gas phase can help explain their high abundances as observed toward hot molecular cores and underlines their importance in astrobiology.
Ribose and related sugars from ultraviolet irradiation of interstellar ice analogs
Science, 2016
Materials and Methods Preparation of the interstellar pre-cometary ice analogue The experimental setup has already been described in detail elsewhere (30). It consists of a high vacuum chamber (10-7 mbar) in which an infrared (IR) transparent MgF 2 window is cooled down to 78 K. A gas mixture, previously prepared in an independent stainless steel gas line pumped down to about 5.10-6 mbar, is then injected into the chamber where it condenses on the cold MgF 2 substrate to form a thin film of "ices". These ices were, simultaneously to their deposition, irradiated by UV photons for 142 h, using an H 2 discharge lamp providing essentially Lyman-α photons at 122 nm with a tail including an H 2 recombination line at approximately 160 nm and a continuum down to the visible range. In our experiments the ratio of ultraviolet photons to deposited molecules is around 1, meaning approximately 10 eV per deposited molecule to obtain the soluble organic matter sample. The sample was further irradiated, at room temperature, with right-hand circularly polarized synchrotron radiation (CPSR) at 10.2 eV for 2 h at the beamline DESIRS (31) of the SOLEIL synchrotron because we initially intended to induce asymmetric photochemical reactions. At this level of interpretation, no stereochemical effects induced by CPSR could be definitely identified yet in our samples. The entire experiment in terms of deposition rate, ice mixture, and the effect of UV photolysis is constantly monitored by IR spectroscopy which reveals the presence of a few photochemical produced molecules and radicals such as CO, CO 2 , HCO, and H 2 CO, trapped in the ice phase. Photon-molecule interactions are assumed to occur predominantly in the condensed phase but in rare events UV photons may have initiated gas-phase reactions, with the photo-products being subsequently trapped on the ices. For this study, we prepared one mixture composed of H 2 O, 13 CH 3 OH, and NH 3 in relative proportions 10:3.5:1, qualitatively representative of interstellar/pre-cometary ices. Methanol, our only source of carbon, was labelled with 13 C in order to avoid any confusion with potential biological contamination in the handling and analysis processes of the samples. H 2 O (water, liquid) was purified by using a Millipore Direct Q5 system, 13 CH 3 OH (methanol, liquid) was purchased from Aldrich (99.9% purity), and NH 3 (ammonia, gas) from Messer (99.98% purity). The ratios between the components were determined by their partial pressures in the gas line, measured by an absolute pressure gauge (Baratron). The physico-chemical state of the initial sample (temperature and ice composition) is used as a template of pre-accretionary ices and is not fully representative of interstellar conditions. At 78 K, enhanced diffusion of reactants allows for a faster chemical evolution than at 10 K without significantly affecting the nature of the organic residue (32). The organic residue is always extracted after warm-up to room temperature as when considering the chemical composition of meteorites. For the initial molecular ice composition, we observed that CO and CO 2 13 C isotopologues appear during the photochemical process, formed and trapped in the ice and are thus part of the icy molecular chemical reservoir. During the preparation of the samples infrared monitoring is used to control deposition rate and UV efficiency by using the apparition of a weak HCO band and a reasonably strong H 2 CO band, which falls at 1720 cm-1. The 3.4-µm feature, which consists of two subfeatures at 2925 cm-1 (3.42 µm) and 2875 cm-1 (3.48 µm) indicative to the presence of CH 2 OH groups (33), was recorded in our ice
Astrobiology, 2010
More than 50 stable organic molecules have been detected in the interstellar medium (ISM), from ground-based and onboard-satellite astronomical observations, in the gas and solid phases. Some of these organics may be prebiotic compounds that were delivered to early Earth by comets and meteorites and may have triggered the first chemical reactions involved in the origin of life. Ultraviolet irradiation of ices simulating photoprocesses of cold solid matter in astrophysical environments have shown that photochemistry can lead to the formation of amino acids and related compounds. In this work, we experimentally searched for other organic molecules of prebiotic interest, namely, oxidized acid labile compounds. In a setup that simulates conditions relevant to the ISM and Solar System icy bodies such as comets, a condensed CH 3 OH:NH 3 ¼ 1:1 ice mixture was UV irradiated at *80 K. The molecular constituents of the nonvolatile organic residue that remained at room temperature were separated by capillary gas chromatography and identified by mass spectrometry. Urea, glycolic acid, and glycerol were detected in this residue, as well as hydroxyacetamide, glycerolic acid, and glycerol amide. These organics are interesting target molecules to be searched for in space. Finally, tentative mechanisms of formation for these compounds under interstellar=pre-cometary conditions are proposed.
Proceedings of the National Academy of Sciences of the United States of America, 2015
Evolved interstellar ices observed in dense protostellar molecular clouds may arguably be considered as part of precometary materials that will later fall on primitive telluric planets, bringing a wealth of complex organic compounds. In our laboratory, experiments reproducing the photo/thermochemical evolution of these ices are routinely performed. Following previous amino acid identifications in the resulting room temperature organic residues, we have searched for a different family of molecules of potential prebiotic interest. Using multidimensional gas chromatography coupled to time-of-flight mass spectrometry, we have detected 10 aldehydes, including the sugar-related glycolaldehyde and glyceraldehyde--two species considered as key prebiotic intermediates in the first steps toward the synthesis of ribonucleotides in a planetary environment. The presence of ammonia in water and methanol ice mixtures appears essential for the recovery of these aldehydes in the refractory organic r...
On the Production of Polyols and Hydroxycarboxylic Acids in Interstellar Analogous Ices of Methanol
The Astrophysical Journal, 2020
This laboratory work studied the production of complex organic molecules (COMs) in pure methanol (CH3OH) ices exposed to ionizing radiation in the form of energetic electrons. The chemical evolution of the ices during the electron irradiation at 10 K and subsequent warm-up phase to 300 K was monitored online and in situ via Fourier Transform Infrared (FTIR) spectrometry. Polyols and hydroxycarboxylic acids related absorptions were observed in the infrared spectra of the irradiated ices and residues at room temperature. The residues were analyzed via two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Four polyols and five hydroxycarboxylic acids were detected. All of these compounds except 1,3-propanediol and 1,3-butanediol have been identified in the Murchison and Bell meteorites. The most abundant species, ethylene glycol, has also been found in the ISM. Our findings suggest that other polyols and acids may also be present in methanol-rich starforming regions. The non-detection of higher order sugars, as those found in the ultraviolet (UV) photon processed 13 C-methanol (13 CH3OH):water (H2O):ammonia (NH3) and 13 C-methanol (13 CH3OH):water (H2O) ice mixtures, indicates that the type of radiation source or more likely the prevalent NH3 and/or H2O molecules in the ISM are critical to the abiotic formation of the bio-essential sugars. Experiments are currently being designed to elucidate the roles of each component.
Organic residues from ultraviolet irradiation of interstellar ice analogs
EAS Publications Series, 2012
Interstellar ices are widely observed in the infrared spectra of regions where stars and planetary systems form. Photochemical and thermal evolution of these ices is simulated and studied in our laboratory where the resulting production of complex organic residues is routinely performed. Observations of their variability with slightly different starting chemical conditions can be performed by means of infrared spectroscopy. Organic residues have interesting chemical properties that make them good potential candidates for prebiotic chemistry. Numerous other analytical methods (GC-MS, HPLC, mass spectrometry, etc.) can be combined to refine the knowledge of their chemical composition and structure. We present here some results on the obtained organic residue resulting from subsequent heating and sublimation of the irradiated ices which show the formation of some macromolecular species.
Monthly Notices of the Royal Astronomical Society
Soluble and insoluble organic matter (IOM) is a key feature of primitive carbonaceous chondrites. We observe the formation of organic materials in the photothermochemical treatment of astrophysical ices in the laboratory. Starting from a low vacuum ultraviolet (VUV) irradiation dose on templates of astrophysical ices at 77 K, we obtain first a totally soluble form of organic matter at room temperature. Once this organic residue is formed, irradiating it further in vacuum results in the production of a thin altered dark crust on top of the initial soluble one. The whole residue is studied here by non-destructive methods inducing no alteration of samples, visible microscopy and mid-infrared (micro-)spectroscopy. After water extraction of the soluble part, an insoluble fraction remains on the sample holder which provides a largely different infrared spectrum when compared to the one of the soluble sample. Therefore, from the same VUV and thermal processing of initial simple ices, we produce first a soluble material from which a much larger irradiation dose leads to an insoluble one. Interestingly, this insoluble fraction shows some spectral similarities with natural samples of IOM extracted from two meteorites (Tagish Lake and Murchison), selected as examples of primitive materials. It suggests that the organic molecular diversity observed in meteorites may partly originate from the photo and thermal processing of interstellar/circum-stellar ices at the final stages of molecular cloud evolution towards the build-up of our Solar system.
Journal of Molecular Spectroscopy, 2022
The astrochemistry of CO2 ice analogues has been a topic of intensive investigation due to the prevalence of CO2 throughout the interstellar medium and the Solar System, as well as the possibility of it acting as a carbon feedstock for the synthesis of larger, more complex organic molecules. In order to accurately discern the physico-chemical processes in which CO2 plays a role, it is necessary to have laboratory-generated spectra to compare against observational data acquired by ground-and space-based telescopes. A key factor which is known to influence the appearance of such spectra is temperature, especially when the spectra are acquired in the infrared and ultraviolet. In this present study, we describe the results of a systematic investigation looking into: (i) the influence of thermal annealing on the mid-IR and VUV absorption spectra of pure, unirradiated CO2 astrophysical ice analogues prepared at various temperatures, and (ii) the influence of temperature on the chemical products of electron irradiation of similar ices. Our results indicate that both mid-IR and VUV spectra of pure CO2 ices are sensitive to the structural and chemical changes induced by thermal annealing. Furthermore, using mid-IR spectroscopy, we have successfully identified the production of radiolytic daughter molecules as a result of 1 keV electron irradiation and the influence of temperature over this chemistry. Such results are directly applicable to studies on the chemistry of interstellar ices, comets, and icy lunar objects and may also be useful as reference data for forthcoming observational missions.