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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Origins of life and evolution of the biospheres 27 (1997), S. 23-51 
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We review the formation and evolution of complex circumstellar and interstellar molecules. A number of promising chemical routes are discussed which may lead to the formation of polycyclic aromatic hydrocarbon molecules, fullerenes, and unsaturated hydrocarbon chains in the outflows from stars. Some of the problems with these chemical schemes are pointed out as well. We also review the role of grains in the formation of complex molecules in interstellar molecular clouds. This starts with the formation of simple molecules in an ice grain mantle. UV photolysis and/or thermal polymerization can convert some of these simple molecules into more complex polymeric structures. Some of these species may be released to the gas phase, particularly in the warm regions around newly formed stars. Methanol and formaldehyde seem to play an important role in this drive towards molecular complexity and their chemistry is traced in some detail.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 224 (1995), S. 251-254 
    ISSN: 1572-946X
    Keywords: ISM: molecules ; stars: formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent theoretical work on the chemistry in regions of massive star formation is summarised.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 224 (1995), S. 439-440 
    ISSN: 1572-946X
    Keywords: stars: late-type ; stars: circumstellar matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Some results from studies of the gas-grain chemistry in oxygen-rich circumstellar envelopes (CSEs) are presented.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 224 (1995), S. 441-442 
    ISSN: 1572-946X
    Keywords: ISM: molecules ; solar system: formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study has been undertaken of the gas-grain chemistry of protostellar disks which are sufficiently cool that in the outer regions, where the gas density is less than ∼ 1013 cm−3 and the ionization rate highest, a bimolecular chemistry resembling that of dark clouds can occur. Since the gas-grain collision rate is so high, outgassing mantle molecules effectively determine the gas phase composition at any position in the disk. In contrast to previous work, a detailed gas phase chemistry is considered along with the accretion and desorption of mantle species which is controlled locally by the dust temperature.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 224 (1995), S. 443-444 
    ISSN: 1572-946X
    Keywords: ISM: molecules ; ISM: kinematics and dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The small ion-neutral drift speeds attained in MHD waves lead to a significant increase in the rates of several important ion-molecule reactions. The effect on the deuterium chemistry of dark clouds could allow MHD wave motion to be observed directly. The results of some recent observations to test this theory are outlined.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Earth, moon and planets 89 (2000), S. 221-246 
    ISSN: 1573-0794
    Keywords: Comet C/1995 O1 Hale–Bopp ; comets ; laboratory studies ; physico-chemsitry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Until cometary matter can be studied in-situ or cometary samples are brought back to Earth for analysis, theoretical models and laboratory studies remain a crucial tool for revealing the nature of cometary matter. Constraints on the nature of the primordial material available for incorporation into comets and other solar system material comes from analysis of data from space-based and ground-based observatories. The structure of the nuclear ice component, which may have coexisting amorphous/crystalline phases and include clathrates and other trapped guest molecules, strongly influences the cometary outgassing properties. This paper reviews laboratory work on ice and carbon aceous compounds and discusses their significance for cometary chemistry. Special emphasis will be given to studies on the thermal processing of ices and their implications for the structure changes and subsequent release of volatiles. We also describe the preliminary results of a model of nuclear outgassing, and discuss how such model scan be used to infer the chemical structure of the nuclearices. Furthermore, we confront cometary data with the analysis of carbonaceous meteorites. Recent laboratory results on volatile compounds and the macro molecular structure of carbonaceous meteorites allow us to investigate the link of small bodies in the Solar System. Until ROSETTA will land on comet Wirtanen and study directly the nuclear composition, laboratory measurements of ice and refractory analogs will — together with the analysis of meteorites —significantly improve our knowledge on the origin and structure ofcomets.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2010-12-27
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 8
    Publication Date: 2011-01-12
    Description: Polycyclic aromatic hydrocarbons and related species have been suggested to play a key role in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest building block—the aromatic benzene molecule—has remained elusive for decades. Here we demonstrate in crossed molecular beam experiments combined with electronic structure and statistical calculations that benzene (C6H6) can be synthesized via the barrierless, exoergic reaction of the ethynyl radical and 1,3-butadiene, C2H + H2CCHCHCH2 → C6H6 + H, under single collision conditions. This reaction portrays the simplest representative of a reaction class in which aromatic molecules with a benzene core can be formed from acyclic precursors via barrierless reactions of ethynyl radicals with substituted 1,3-butadiene molecules. Unique gas-grain astrochemical models imply that this low-temperature route controls the synthesis of the very first aromatic ring from acyclic precursors in cold molecular clouds, such as in the Taurus Molecular Cloud. Rapid, subsequent barrierless reactions of benzene with ethynyl radicals can lead to naphthalene-like structures thus effectively propagating the ethynyl-radical mediated formation of aromatic molecules in the interstellar medium.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2017-07-29
    Description: Recent simulations have indicated that vinyl cyanide is the best candidate molecule for the formation of cell membranes/vesicle structures in Titan’s hydrocarbon-rich lakes and seas. Although the existence of vinyl cyanide (C 2 H 3 CN) on Titan was previously inferred using Cassini mass spectrometry, a definitive detection has been lacking until now. We report the first spectroscopic detection of vinyl cyanide in Titan’s atmosphere, obtained using archival data from the Atacama Large Millimeter/submillimeter Array (ALMA), collected from February to May 2014. We detect the three strongest rotational lines of C 2 H 3 CN in the frequency range of 230 to 232 GHz, each with 〉4 confidence. Radiative transfer modeling suggests that most of the C 2 H 3 CN emission originates at altitudes of 200 km, in agreement with recent photochemical models. The vertical column densities implied by our best-fitting models lie in the range of 3.7 x 10 13 to 1.4 x 10 14 cm –2 . The corresponding production rate of vinyl cyanide and its saturation mole fraction imply the availability of sufficient dissolved material to form ~10 7 cell membranes/cm 3 in Titan’s sea Ligeia Mare.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 10
    Publication Date: 2005-03-22
    Print ISSN: 0004-6361
    Electronic ISSN: 1432-0746
    Topics: Physics
    Published by EDP Sciences
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