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Merino P, Martínez L, Santoro G, Martínez JI, Lauwaet K, Accolla M, Ruiz Del Arbol N, Sánchez-Sánchez C, Martín-Jimenez A, Otero R, Piantek M, Serrate D, Lebrón-Aguilar R, Quintanilla-López JE, Mendez J, De Andres PL, Martín-Gago JA. n-Alkanes formed by methyl-methylene addition as a source of meteoritic aliphatics. Commun Chem 2024; 7:165. [PMID: 39080475 PMCID: PMC11289383 DOI: 10.1038/s42004-024-01248-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 07/18/2024] [Indexed: 08/02/2024] Open
Abstract
Aliphatics prevail in asteroids, comets, meteorites and other bodies in our solar system. They are also found in the interstellar and circumstellar media both in gas-phase and in dust grains. Among aliphatics, linear alkanes (n-CnH2n+2) are known to survive in carbonaceous chondrites in hundreds to thousands of parts per billion, encompassing sequences from CH4 to n-C31H64. Despite being systematically detected, the mechanism responsible for their formation in meteorites has yet to be identified. Based on advanced laboratory astrochemistry simulations, we propose a gas-phase synthesis mechanism for n-alkanes starting from carbon and hydrogen under conditions of temperature and pressure that mimic those found in carbon-rich circumstellar envelopes. We characterize the analogs generated in a customized sputter gas aggregation source using a combination of atomically precise scanning tunneling microscopy, non-contact atomic force microscopy and ex-situ gas chromatography-mass spectrometry. Within the formed carbon nanostructures, we identify the presence of n-alkanes with sizes ranging from n-C8H18 to n-C32H66. Ab-initio calculations of formation free energies, kinetic barriers, and kinetic chemical network modelling lead us to propose a gas-phase growth mechanism for the formation of large n-alkanes based on methyl-methylene addition (MMA). In this process, methylene serves as both a reagent and a catalyst for carbon chain growth. Our study provides evidence of an aliphatic gas-phase synthesis mechanism around evolved stars and provides a potential explanation for its presence in interstellar dust and meteorites.
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Affiliation(s)
- P Merino
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain.
| | - L Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - G Santoro
- Instituto de Estructura de la Materia (IEM), CSIC, Serrano 121, 28006, Madrid, Spain
| | - J I Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - K Lauwaet
- Instituto Madrileño de Estudios Avanzados IMDEA Nanociencia, Madrid, Spain
| | - M Accolla
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
- INAF-Osservatorio Astrofisico di Catania, Via Santa Sofia 78, 95123, Catania, Italy
| | - N Ruiz Del Arbol
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - C Sánchez-Sánchez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - A Martín-Jimenez
- Instituto Madrileño de Estudios Avanzados IMDEA Nanociencia, Madrid, Spain
| | - R Otero
- Instituto Madrileño de Estudios Avanzados IMDEA Nanociencia, Madrid, Spain
- Dep. De Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049, Madrid, Spain
- IFIMAC, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - M Piantek
- Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, 50018, Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018, Zaragoza, Spain
| | - D Serrate
- Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, 50018, Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018, Zaragoza, Spain
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-UNIZAR, 50009, Zaragoza, Spain
| | - R Lebrón-Aguilar
- Instituto de Química-Física "Blas Cabrera" (IQF), CSIC, Serrano, 119, 28006, Madrid, Spain
| | - J E Quintanilla-López
- Instituto de Química-Física "Blas Cabrera" (IQF), CSIC, Serrano, 119, 28006, Madrid, Spain
| | - J Mendez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - P L De Andres
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - J A Martín-Gago
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
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Zamith S, Kassem A, L'Hermite JM, Joblin C. Water Attachment onto Size-Selected Cationic Pyrene Clusters. J Phys Chem A 2022; 126:3696-3707. [PMID: 35670699 DOI: 10.1021/acs.jpca.2c02195] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report measurements of the attachment rates of water molecules onto mass-selected cationic pyrene clusters for size from n = 4 to 13 pyrene units and for different collision energies. Comparison of the attachment rates with the collision rates measured in collision-induced dissociation experiments provides access to the values of the sticking coefficient. The strong dependence of the attachment rates on size and collision energy is rationalized through a model in which we use a Langevin-type collision rate and adjust on experimental data the statistical dissociation rate of the water molecule from the cluster after attachment. This allows us to extrapolate our results to the conditions of isolation and long time scales encountered in astrophysical environments.
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Affiliation(s)
- Sébastien Zamith
- Laboratoire Collision Agrégats Réactivité (LCAR/IRSAMC), UMR5589, Université de Toulouse III - Paul Sabatier and CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - Ali Kassem
- Laboratoire Collision Agrégats Réactivité (LCAR/IRSAMC), UMR5589, Université de Toulouse III - Paul Sabatier and CNRS, 118 Route de Narbonne, F-31062 Toulouse, France.,Institut de Recherche en Astrophysique et Planétologie (IRAP), UMR5277, Université de Toulouse III - Paul Sabatier, CNRS, CNES, 9 avenue du Colonel Roche, F-31028 Toulouse, France
| | - Jean-Marc L'Hermite
- Laboratoire Collision Agrégats Réactivité (LCAR/IRSAMC), UMR5589, Université de Toulouse III - Paul Sabatier and CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - Christine Joblin
- Institut de Recherche en Astrophysique et Planétologie (IRAP), UMR5277, Université de Toulouse III - Paul Sabatier, CNRS, CNES, 9 avenue du Colonel Roche, F-31028 Toulouse, France
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Cernicharo J, Agúndez M, Cabezas C, Tercero B, Marcelino N, Pardo JR, de Vicente P. Pure hydrocarbon cycles in TMC-1: Discovery of ethynyl cyclopropenylidene, cyclopentadiene and indene. ASTRONOMY AND ASTROPHYSICS 2021; 649:L15. [PMID: 34257463 PMCID: PMC7611194 DOI: 10.1051/0004-6361/202141156] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the detection for the first time in space of three new pure hydrocarbon cycles in TMC-1: c-C3HCCH (ethynyl cyclopropenylidene), c-C5H6 (cyclopentadiene) and c-C9H8 (indene). We derive a column density of 3.1 × 1011 cm-2 for the former cycle and similar values, in the range (1-2) × 1013 cm-2, for the two latter molecules. This means that cyclopentadiene and indene, in spite of their large size, are exceptionally abundant, only a factor of five less abundant than the ubiquitous cyclic hydrocarbon c-C3H2. The high abundance found for these two hydrocarbon cycles, together with the high abundance previously found for the propargyl radical (CH2CCH) and other hydrocarbons like vinyl and allenyl acetylene (Agúndez et al. 2021; Cernicharo et al. 2021a,b), start to allow us to quantify the abundant content of hydrocarbon rings in cold dark clouds and to identify the intermediate species that are probably behind the in situ bottom-up synthesis of aromatic cycles in these environments. While c-C3HCCH is most likely formed through the reaction between the radical CCH and c-C3H2, the high observed abundances of cyclopentadiene and indene are difficult to explain through currently proposed chemical mechanisms. Further studies are needed to identify how are five- and six-membered rings formed under the cold conditions of clouds like TMC-1.
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Affiliation(s)
- J. Cernicharo
- Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/Serrano 121, 28006 Madrid, Spain
| | - M. Agúndez
- Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/Serrano 121, 28006 Madrid, Spain
| | - C. Cabezas
- Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/Serrano 121, 28006 Madrid, Spain
| | - B. Tercero
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
- Observatorio Astronómico Nacional (OAN, IGN), Madrid, Spain
| | - N. Marcelino
- Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/Serrano 121, 28006 Madrid, Spain
| | - J. R. Pardo
- Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/Serrano 121, 28006 Madrid, Spain
| | - P. de Vicente
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
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Peeters E, Mackie C, Candian A, Tielens AGGM. A Spectroscopic View on Cosmic PAH Emission. Acc Chem Res 2021; 54:1921-1933. [PMID: 33780617 DOI: 10.1021/acs.accounts.0c00747] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
ConspectusPolycyclic aromatic hydrocarbon molecules (PAHs) are ubiquitously present at high abundances in the Universe. They are detected through their infrared (IR) fluorescence UV pumped by nearby massive stars. Hence, their infrared emission is used to determine the star formation rate in galaxies, one of the key indicators for understanding the evolution of galaxies. Together with fullerenes, PAHs are the largest molecules found in space. They significantly partake in a variety of physical and chemical processes in space, influencing star and planet formation as well as galaxy evolution.Since the IR features from PAHs originate from chemical bonds involving only nearest neighbor atoms, they have only a weak dependence on the size and structure of the molecule, and it is therefore not possible to identify the individual PAH molecules that make up the cosmic PAH family. This strongly hampers the interpretation of their astronomical fingerprints. Despite the lack of identification, constraints can be set on the characteristics of the cosmic PAH family thanks to a joint effort of astronomers, physicists, and chemists.This Account presents the spectroscopic properties of the cosmic PAH emission as well as the intrinsic spectroscopic properties of PAHs and astronomical modeling of the PAH evolution required for the interpretation of the cosmic PAH characteristics. We discuss the observed spectral signatures tracing PAH properties such as charge, size, and structure and highlight the related challenges. We discuss the recent success of anharmonic calculations of PAH infrared absorption and emission spectra and outline the path forward. Finally, we illustrate the importance of models on PAH processing for the interpretation of the astronomical data in terms of the charge balance and PAH destruction.Throughout this Account, we emphasize that huge progress is on the horizon on the astronomical front. Indeed, the world is eagerly awaiting the launch of the James Webb Space Telescope (JWST). With its incredible improvement in spatial resolution, combined with its complete spectral coverage of the PAH infrared emission bands at medium spectral resolution and superb sensitivity, the JWST will revolutionize PAH research. Previous observations could only present spectra averaged over regions with vastly different properties, thus greatly confusing their interpretation. The amazing spatial resolution of JWST will disentangle these different regions. This will allow us to quantify precisely how PAHs are modified by the physical conditions of their host environment and thus trace how PAHs evolve across space. However, this will only be achieved when the necessary (and still missing) fundamental properties of PAHs, outlined in this Account, are known. We strongly encourage you to join this effort.
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Affiliation(s)
- Els Peeters
- Department of Physics & Astronomy, University of Western Ontario, London, Ontario, Canada
- Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada
- SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, California 94043, United States
| | - Cameron Mackie
- Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States
| | - Alessandra Candian
- van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Amsterdam, The Netherlands
- Leiden Observatory, Leiden University, Leiden, The Netherlands
| | - Alexander G. G. M. Tielens
- Leiden Observatory, Leiden University, Leiden, The Netherlands
- University of Maryland, College Park, Maryland 20742, United States
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Zhang D, Yang Y, Hu X, Zhen J. Gas phase formation of carbon cluster (fullerenes and graphenes)/prebiotic sugar complexes. Phys Chem Chem Phys 2021; 23:1424-1436. [PMID: 33393943 DOI: 10.1039/d0cp04366d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Among the constituent molecular classes of proteins and nucleic acids, the presence of Ribose and deoxy-Ribose in space remains unclear. Here, we provide experimental evidence of astronomically related sugar derivatives - carbon cluster (fullerenes and graphenes)/prebiotic sugar complexes - and study their formation processes in the gas phase. The results show that, with PAH cations (dicoronylene, DC, C48H20+)/(2-deoxy-d-Ribose, dR, C5H10O4, and dehydrated 2-deoxy-d-Ribose, DedR, C5H8O3) and fullerene cations (C60+)/(dR and DedR) as the initial molecular precursors, two series of graphene-prebiotic sugar cluster cations (graphene/dR and graphene/DedR, e.g., (dR)Cn+ and (DedR)Cn+) and two series of fullerene-prebiotic sugar cluster cations (fullerene/dR and fullerene/DedR, e.g., (dR)(DedR)2Cn+, (DedR)3Cn+, and (dR)2(DedR)Cn+) are formed through an ion-molecule reaction pathway under the influence of a strong radiation field. The structures of the newly formed complexes and the binding energies of these formation reactions are initially theoretically calculated. These laboratory studies attest to the importance of ion-molecule reaction synthesis routes for the chemical complexity in space, demonstrating that the gas phase interstellar materials could directly lead to the formation of large and complex sugar derivatives in a bottom-up growth process. The chemical evolution in space in which single molecules are transformed into complex molecules produces a wide variety of organic compounds (e.g., carbon cluster (fullerenes and graphenes)/prebiotic sugar complexes). For their astrobiological implications, this opens up aromatic based biogenic chemistry that is available to the parent of PAHs or fullerenes in the interstellar environments.
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Affiliation(s)
- Deping Zhang
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, China. and School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China
| | - Yuanyuan Yang
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, China. and School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoyi Hu
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, China. and School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China
| | - Junfeng Zhen
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, China. and School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China
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Santoro G, Martínez L, Lauwaet K, Accolla M, Tajuelo-Castilla G, Merino P, Sobrado JM, Peláez RJ, Herrero VJ, Tanarro I, Mayoral ÁL, Agúndez M, Sabbah H, Joblin C, Cernicharo J, Martín-Gago JÁ. The Chemistry of Cosmic Dust Analogues from C, C 2, and C 2H 2 in C-Rich Circumstellar Envelopes. THE ASTROPHYSICAL JOURNAL 2020; 895:97. [PMID: 33154601 PMCID: PMC7116318 DOI: 10.3847/1538-4357/ab9086] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Interstellar carbonaceous dust is mainly formed in the innermost regions of circumstellar envelopes around carbon-rich asymptotic giant branch (AGB) stars. In these highly chemically stratified regions, atomic and diatomic carbon, along with acetylene are the most abundant species after H2 and CO. In a previous study, we addressed the chemistry of carbon (C and C2) with H2 showing that acetylene and aliphatic species form efficiently in the dust formation region of carbon-rich AGBs whereas aromatics do not. Still, acetylene is known to be a key ingredient in the formation of linear polyacetylenic chains, benzene and polycyclic aromatic hydrocarbons (PAHs), as shown by previous experiments. However, these experiments have not considered the chemistry of carbon (C and C2) with C2H2. In this work, by employing a sufficient amount of acetylene, we investigate its gas-phase interaction with atomic and diatomic carbon. We show that the chemistry involved produces linear polyacetylenic chains, benzene and other PAHs, which are observed with high abundances in the early evolutionary phase of planetary nebulae. More importantly, we have found a non-negligible amount of pure and hydrogenated carbon clusters as well as aromatics with aliphatic substitutions, both being a direct consequence of the addition of atomic carbon. The incorporation of alkyl substituents into aromatics can be rationalized by a mechanism involving hydrogen abstraction followed by methyl addition. All the species detected in gas phase are incorporated into the nanometric sized dust analogues, which consist of a complex mixture of sp, sp2 and sp3 hydrocarbons with amorphous morphology.
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Affiliation(s)
- Gonzalo Santoro
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - Lidia Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - Koen Lauwaet
- IMDEA Nanociencia. Ciudad Universitaria de Cantoblanco, 28049 Cantoblanco, Madrid, Spain
| | - Mario Accolla
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - Guillermo Tajuelo-Castilla
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - Pablo Merino
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics. c/ Serrano 123, 28006 Madrid, Spain
| | - Jesús M. Sobrado
- Centro de Astrobiología (CAB. INTA-CSIC). Crta- de Torrejón a Ajalvir km4, 28850, Torrejón de Ardoz, Madrid, Spain
| | - Ramón J. Peláez
- Instituto de Estructura de la Materia (IEM.CSIC). Molecular Physics Department. c/Serrano 123, 28006 Madrid, Spain
| | - Víctor J. Herrero
- Instituto de Estructura de la Materia (IEM.CSIC). Molecular Physics Department. c/Serrano 123, 28006 Madrid, Spain
| | - Isabel Tanarro
- Instituto de Estructura de la Materia (IEM.CSIC). Molecular Physics Department. c/Serrano 123, 28006 Madrid, Spain
| | - Á lvaro Mayoral
- School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Road, Pudong, Shanghai, 201210, Peoples Republic of China
| | - Marcelino Agúndez
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics. c/ Serrano 123, 28006 Madrid, Spain
| | - Hassan Sabbah
- IRAP, Université de Toulouse, CNRS, CNES. 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France
| | - Christine Joblin
- IRAP, Université de Toulouse, CNRS, CNES. 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France
| | - José Cernicharo
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics. c/ Serrano 123, 28006 Madrid, Spain
| | - José Ángel Martín-Gago
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
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Murga MS, Wiebe DS, Vasyunin AI, Varakin VN, Stolyarov AV. Experimental and theoretical studies of photoinduced reactions in the solid phase of the interstellar medium. RUSSIAN CHEMICAL REVIEWS 2020. [DOI: 10.1070/rcr4912] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Campisi D, Candian A. Do defects in PAHs promote catalytic activity in space? Stone-Wales pyrene as a test case. Phys Chem Chem Phys 2020; 22:6738-6748. [PMID: 32167097 DOI: 10.1039/c9cp06523g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using density functional theory (DFT), we studied the formation of Stone-Wales defects in pyrene, as a prototype PAH molecule. In addition, we studied the reactivity of the defective and pristine pyrenes toward hydrogenation, a process that can occur in some regions of the interstellar medium. We found that the formation of the defect requires overcoming energies of the order of 8.4 eV, but the defective structure is stable due to the high reverse reaction barrier (approx. 6 eV). We also found that the presence of the defect decreases the sticking barrier for the first hydrogenation and promotes more stable singly and doubly hydrogenated intermediates with respect to that of the pristine pyrene. Finally, our results show that both Stone-Wales pyrene and pristine pyrenes can lead to the formation of H2 through an extraction mechanism involving H atoms attached on distal carbon atoms with energy barriers below 2 eV.
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Affiliation(s)
- Dario Campisi
- Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands.
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Foschino S, Berné O, Joblin C. Learning mid-IR emission spectra of polycyclic aromatic hydrocarbon populations from observations. ASTRONOMY AND ASTROPHYSICS 2019; 632:A84. [PMID: 33154596 PMCID: PMC7116302 DOI: 10.1051/0004-6361/201935085] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
CONTEXT The James Webb Space Telescope (JWST) will deliver an unprecedented quantity of high-quality spectral data over the 0.6-28 μm range. It will combine sensitivity, spectral resolution, and spatial resolution. Specific tools are required to provide efficient scientific analysis of such large data sets. AIMS Our aim is to illustrate the potential of unsupervised learning methods to get insights into chemical variations in the populations that carry the aromatic infrared bands (AIBs), more specifically polycyclic aromatic hydrocarbon (PAH) species and carbonaceous very small grains (VSGs). METHODS We present a method based on linear fitting and blind signal separation for extracting representative spectra for a spectral data set. The method is fast and robust, which ensures its applicability to JWST spectral cubes. We tested this method on a sample of ISO-SWS data, which resemble most closely the JWST spectra in terms of spectral resolution and coverage. RESULTS Four representative spectra were extracted. Their main characteristics appear consistent with previous studies with populations dominated by cationic PAHs, neutral PAHs, evaporating VSGs, and large ionized PAHs, known as the PAH x population. In addition, the 3 μm range, which is considered here for the first time in a blind signal separation (BSS) method, reveals the presence of aliphatics connected to neutral PAHs. Each representative spectrum is found to carry second-order spectral signatures (e.g., small bands), which are connected with the underlying chemical diversity of populations. However, the precise attribution of theses signatures remains limited by the combined small size and heterogeneity of the sample of astronomical spectra available in this study. CONCLUSIONS The upcoming JWST data will allow us to overcome this limitation. The large data sets of hyperspectral images provided by JWST analysed with the proposed method, which is fast and robust, will open promising perspectives for our understanding of the chemical evolution of the AIB carriers.
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Affiliation(s)
- S Foschino
- Institut de Recherche en Astrophysique et Planetologie, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France, 9 Av. du colonel Roche, 31028 Toulouse Cedex 04, France
| | - O Berné
- Institut de Recherche en Astrophysique et Planetologie, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France, 9 Av. du colonel Roche, 31028 Toulouse Cedex 04, France
| | - C Joblin
- Institut de Recherche en Astrophysique et Planetologie, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France, 9 Av. du colonel Roche, 31028 Toulouse Cedex 04, France
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Affiliation(s)
- Christine Joblin
- Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse (UPS), CNRS, 31028 Toulouse Cedex 4, France.
| | - José Cernicharo
- Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Molecular Astrophysics Group, Cantoblanco, 28049 Madrid, Spain
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Near-infrared to Mid-infrared Observations of Galaxy Mergers: NGC 2782 and NGC 7727. ACTA ACUST UNITED AC 2018. [DOI: 10.3847/1538-4357/aaa004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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12
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Wakelam V, Bron E, Cazaux S, Dulieu F, Gry C, Guillard P, Habart E, Hornekær L, Morisset S, Nyman G, Pirronello V, Price SD, Valdivia V, Vidali G, Watanabe N. H 2 formation on interstellar dust grains: The viewpoints of theory, experiments, models and observations. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.molap.2017.11.001] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Bujarrabal V, Castro-Carrizo A, Alcolea J, Santander-García M, Van Winckel H, Sánchez Contreras C. Further ALMA observations and detailed modeling of the Red Rectangle. ASTRONOMY AND ASTROPHYSICS 2016; 593:A92. [PMID: 28003685 PMCID: PMC5166967 DOI: 10.1051/0004-6361/201628546] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
AIMS We aim to study the rotating and expanding gas in the Red Rectangle, which is a well known object that recently left the asymptotic giant branch (AGB) phase. We analyze the properties of both components and the relation between them. Rotating disks have been very elusive in post-AGB nebulae, in which gas is almost always found to be in expansion. METHODS We present new high-quality ALMA observations of C17O J=6-5 and H13CN J=4-3 line emission and results from a new reduction of already published 13CO J=3-2 data. A detailed model fitting of all the molecular line data, including previous maps and single-dish observations of lines of CO, CII, and CI, was performed using a sophisticated code that includes an accurate nonlocal treatment of radiative transfer in 2D. These observations (of low- and high-opacity lines requiring various degrees of excitation) and the corresponding modeling allowed us to deepen the analysis of the nebular properties. We also stress the uncertainties, particularly in the determination of the boundaries of the CO-rich gas and some properties of the outflow. RESULTS We confirm the presence of a rotating equatorial disk and an outflow, which is mainly formed of gas leaving the disk. The mass of the disk is ~ 0.01 M⊙, and that of the CO-rich outflow is around ten times smaller. High temperatures of ≳ 100 K are derived for most components. From comparison of the mass values, we roughly estimate the lifetime of the rotating disk, which is found to be of about 10000 yr. Taking data of a few other post-AGB composite nebulae into account, we find that the lifetimes of disks around post-AGB stars typically range between 5000 and more than 20000 yr. The angular momentum of the disk is found to be high, ~ 9 M⊙ AU km s-1, which is comparable to that of the stellar system at present. Our observations of H13CN show a particularly wide velocity dispersion and indicate that this molecule is only abundant in the inner Keplerian disk, at ≲ 60 AU from the stellar system. We suggest that HCN is formed in a dense photodissociation region (PDR) due to the UV excess known to be produced by the stellar system, following chemical mechanisms that are well established for interstellar medium PDRs and disks orbiting young stars. We further suggest that this UV excess could lead to an efficient formation and excitation of PAHs and other C-bearing macromolecules, whose emission is very intense in the optical counterpart.
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Affiliation(s)
- V Bujarrabal
- Observatorio Astronómico Nacional (OAN-IGN), Apartado 112, E-28803 Alcalá de Henares, Spain
| | - A Castro-Carrizo
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406, Saint Martin d'Hères, France
| | - J Alcolea
- Observatorio Astronómico Nacional (OAN-IGN), C/ Alfonso XII, 3, E-28014 Madrid, Spain
| | - M Santander-García
- Observatorio Astronómico Nacional (OAN-IGN), C/ Alfonso XII, 3, E-28014 Madrid, Spain; Instituto de Ciencia de Materiales de Madrid (CSIC). Calle Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - H Van Winckel
- Instituut voor Sterrenkunde, K.U.Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
| | - C Sánchez Contreras
- Centro de Astrobiología (CSIC-INTA), ESAC Campus, E-28691 Villanueva de la Cañada, Madrid, Spain
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The sequence to hydrogenate coronene cations: A journey guided by magic numbers. Sci Rep 2016; 6:19835. [PMID: 26821925 PMCID: PMC4731771 DOI: 10.1038/srep19835] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 11/27/2015] [Indexed: 11/09/2022] Open
Abstract
The understanding of hydrogen attachment to carbonaceous surfaces is essential to a wide variety of research fields and technologies such as hydrogen storage for transportation, precise localization of hydrogen in electronic devices and the formation of cosmic H2. For coronene cations as prototypical Polycyclic Aromatic Hydrocarbon (PAH) molecules, the existence of magic numbers upon hydrogenation was uncovered experimentally. Quantum chemistry calculations show that hydrogenation follows a site-specific sequence leading to the appearance of cations having 5, 11, or 17 hydrogen atoms attached, exactly the magic numbers found in the experiments. For these closed-shell cations, further hydrogenation requires appreciable structural changes associated with a high transition barrier. Controlling specific hydrogenation pathways would provide the possibility to tune the location of hydrogen attachment and the stability of the system. The sequence to hydrogenate PAHs, leading to PAHs with magic numbers of H atoms attached, provides clues to understand that carbon in space is mostly aromatic and partially aliphatic in PAHs. PAH hydrogenation is fundamental to assess the contribution of PAHs to the formation of cosmic H2.
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