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Title: A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules

Authors:
; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1260424
Grant/Contract Number:
FG02-05ER15685
Resource Type:
Journal Article: Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 28; Related Information: CHORUS Timestamp: 2017-06-24 13:53:39; Journal ID: ISSN 0027-8424
Publisher:
Proceedings of the National Academy of Sciences
Country of Publication:
United States
Language:
English

Citation Formats

Abplanalp, Matthew J., Gozem, Samer, Krylov, Anna I., Shingledecker, Christopher N., Herbst, Eric, and Kaiser, Ralf I.. A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules. United States: N. p., 2016. Web. doi:10.1073/pnas.1604426113.
Abplanalp, Matthew J., Gozem, Samer, Krylov, Anna I., Shingledecker, Christopher N., Herbst, Eric, & Kaiser, Ralf I.. A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules. United States. doi:10.1073/pnas.1604426113.
Abplanalp, Matthew J., Gozem, Samer, Krylov, Anna I., Shingledecker, Christopher N., Herbst, Eric, and Kaiser, Ralf I.. 2016. "A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules". United States. doi:10.1073/pnas.1604426113.
@article{osti_1260424,
title = {A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules},
author = {Abplanalp, Matthew J. and Gozem, Samer and Krylov, Anna I. and Shingledecker, Christopher N. and Herbst, Eric and Kaiser, Ralf I.},
abstractNote = {},
doi = {10.1073/pnas.1604426113},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 28,
volume = 113,
place = {United States},
year = 2016,
month = 7
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1073/pnas.1604426113

Citation Metrics:
Cited by: 14works
Citation information provided by
Web of Science

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  • The hunt for complex organic molecules (COMs) is a major concern for understanding the possible role of interstellar chemistry in the synthesis of the molecules that ultimately may be at the origin of life. A comprehensive screening of the 14 species effectively observed under 32 different isomeric forms in the interstellar medium has been done by means of high-level quantum chemical simulations. Confrontation between calculations and observations shows that when several isomers of the same generic formula are identified, it is always the most stable one that is the most abundant. Moreover, the abundance ratio of the most stable isomermore » to the other isomers is directly related to their energy difference. What can be seen as a minimum energy principle is verified in molecular clouds, hot cores/corinos, photodissociation regions, and asymptotic giant branch stars. The few exceptions encountered could be rationalized either by the existence of different routes of formation with no intermediate in common and/or specific depletion on the grains of one isomer with respect to the others.« less
  • 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 ismore » 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{sub 2}O, NH{sub 3}, CO{sub 2}, H{sub 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.« less
  • Smith and Adams have recently proposed that radiative association reactions can proceed rapidly at the low temperatures found in interstellar clouds. We propose radiative association reactions of CH/sub 3//sup +/, CH/sub 3/O/sup +/, CH/sub 3/CO/sup +/, CH/sub 5//sup +/, HCO/sup +/, NO/sup +/, and H/sub 2/CN/sup +/, and several bimolecular reactions of CH/sub 3//sup +/, C/sub 2/H/sub 2//sup +/, and NH/sub 3//sup +/, which, if they occur at the low temperatures of interstellar molecular clouds, can effectively synthesize a large number of the more complex interstellar species including CH/sub 4/, NH/sub 3/, CH/sub 3/OH, CH/sub 2/O, CH/sub 2/CO, CH/sub 3/CHO,more » CH/sub 3/CH/sub 2/OH, CH/sub 3/OCH/sub 3/, CH/sub 3/OOCH, CH/sub 2/,NH, CH/sub 3/NH/sub 2/, CH/sub 3/CN, HCOOH, HNCO, NH/sub 2/CN, CH/sub 3/C/sub 2/H, and HNO. New laboratory data are required in order to verify that these species can be synthesized by the proposed reactions. It appears, however, that gas-phase ion chemistry may indeed be capable of synthesizing the most complex of interstellar molecules.« less
  • A detailed model for the gas-phase chemistry of dense interstellar clouds is presented which includes, for the first time, reactions that both produce and destroy a representative sample of complex molecular species. In the model, which includes 200 species and over 1800 gas-phase reactions, an initial set of atomic and molecular abundances is allowed to evolve under constant physical conditions and in the absence of photodissociations. Our results indicate that, under these conditions, complex molecular species can be produced via gas-phase chemistry at abundances near observed valus but typically at times before steady state is reached and that their abundancesmore » attain a maximum value at times somewhat after the atomic carbon (C I) abundance peaks and begins to decrease. Since the steady-state abundances of most complex molecules are calculated to be significantly lower than observed values, it is concluded that although high gas density, low temperature, and shielding from ultraviolet radiation provide favorable environment for the synthesis of complex molecules, under nonequilibrium conditions significant production of complex molecules occurs only when the C I abundance is high and when the (C)/(CO) ratio is of order unity. The observational implications are discussed. No firm conclusion about cloud lifetimes can be drawn from this model until the time dependence of physical conditions is also treated. Finally, our results are compared with observations in the molecular clouds TMC-1, Orion (ridge), and Sgr B2.« less
  • The possible synthesis of organic molecules by the absorption of galactic cosmic rays in an N2-CH4-H2 Titan model atmosphere has been studied. The cosmic-ray-induced ionization results in peak electron densities of 2000/cu cm, with NH(+), C3H9(+), and C4H9(+) being among the important positive ions. Details of the ion and neutral chemistry relevant to the production of organic molecules are discussed. The potential importance of N(2D) reactions with CH4 and H2 is also demonstrated. Although the integrated production rate of organic matter due to the absorption of the cosmic ray cascade is much less than that by solar ultraviolet radiation, themore » production of nitrogen-bearing organic molecules by cosmic rays may be greater.« less