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Toumi A, Couturier-Tamburelli I, Chiavassa T, Piétri N. Photolysis of Astrophysically Relevant Acrylonitrile: A Matrix Experimental Study. J Phys Chem A 2014; 118:2453-62. [DOI: 10.1021/jp412481s] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- A. Toumi
- Aix-Marseille Université, CNRS, PIIM, UMR 7345, 13397 Marseille, France
| | | | - T. Chiavassa
- Aix-Marseille Université, CNRS, PIIM, UMR 7345, 13397 Marseille, France
| | - N. Piétri
- Aix-Marseille Université, CNRS, PIIM, UMR 7345, 13397 Marseille, France
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Saidani G, Kalugina Y, Gardez A, Biennier L, Georges R, Lique F. High temperature reaction kinetics of CN(v = 0) with C2H4 and C2H6 and vibrational relaxation of CN(v = 1) with Ar and He. J Chem Phys 2013; 138:124308. [DOI: 10.1063/1.4795206] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Moses JI, Visscher C, Keane TC, Sperier A. On the abundance of non-cometary HCN on Jupiter. Faraday Discuss 2011; 147:103-36; discussion 251-82. [PMID: 21302544 DOI: 10.1039/c003954c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using one-dimensional thermochemical/photochemical kinetics and transport models, we examine the chemistry of nitrogen-bearing species in the Jovian troposphere in an attempt to explain the low observational upper limit for HCN. We track the dominant mechanisms for interconversion of N2-NH3 and HCN-NH3 in the deep, high-temperature troposphere and predict the rate-limiting step for the quenching of HCN at cooler tropospheric altitudes. Consistent with some other investigations that were based solely on time-scale arguments, our models suggest that transport-induced quenching of thermochemically derived HCN leads to very small predicted mole fractions of hydrogen cyanide in Jupiter's upper troposphere. By the same token, photochemical production of HCN is ineffective in Jupiter's troposphere: CH4-NH3 coupling is inhibited by the physical separation of the CH4 photolysis region in the upper stratosphere from the NH3 photolysis and condensation region in the troposphere, and C2H2-NH3 coupling is inhibited by the low tropospheric abundance of C2H2. The upper limits from infrared and submillimetre observations can be used to place constraints on the production of HCN and other species from lightning and thundershock sources.
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Affiliation(s)
- Julianne I Moses
- Space Science Institute, 1602 Old Orchard Ln, Seabrook, TX 77586, USA.
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Gannon KL, Blitz MA, Pilling MJ, Seakins PW, Klippenstein SJ, Harding LB. Kinetics and product branching ratios of the reaction of (1)CH2 with H2 and D2. J Phys Chem A 2008; 112:9575-83. [PMID: 18714945 DOI: 10.1021/jp803038s] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reactions of singlet methylene (a(1)A1 (1)CH2) with hydrogen and deuterium have been studied by experimental and theoretical techniques. The rate coefficients for the removal of singlet methylene with H2 (k1) and D2 (k2) have been measured from 195 to 798 K and are essentially temperature-independent with values of k1 = (10.48 +/- 0.32) x 10(-11) cm(3) molecule(-1) s(-1) and k2 = (5.98 +/- 0.34) x 10(-11) cm(3) molecule(-1) s(-1), where the errors represent 2sigma, giving a ratio of k1/k2 = 1.75 +/- 0.11. In the reaction with H2, singlet methylene can be removed by reaction giving CH3 + H or deactivated to ground-state triplet methylene. Direct measurement of the H atom product showed that the fraction of relaxation decreased from 0.3 at 195 K to essentially zero at 398 K. For the reaction with deuterium, either H or D may be eliminated. Experimentally, the H:D ratio was determined to be 1.8 +/- 0.5 over the range 195-398 K. Theoretically, the reaction kinetics has been predicted with variable reaction coordinate transition state theory and with rigid-body trajectory simulations employing various high-level, ab initio-determined potential energy surfaces. The magnitudes of the calculated rate coefficients are in agreement with experiment, but the calculations show a significant negative temperature dependence that is not observed in the experimental results. The calculated and experimental H to D ratios from the reaction of singlet methylene with D2 are in good agreement, suggesting that the reaction proceeds entirely through the formation of a long-lived methane intermediate with a statistical distribution of energy.
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Affiliation(s)
- K L Gannon
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
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Osamura Y, Petrie S. NCCN and NCCCCN Formation in Titan's Atmosphere: 1. Competing Reactions of Precursor HCCN (3A‘ ‘) with H (2S) and CH3(2A‘). J Phys Chem A 2004. [DOI: 10.1021/jp037817+] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Wilson EH. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003je002181] [Citation(s) in RCA: 285] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Choi N, Blitz M, McKee K, Pilling M, Seakins P. H atom branching ratios from the reactions of CN radicals with C2H2 and C2H4. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2003.11.100] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Thorn, RP, Payne, WA, Chillier XDF, Stief LJ, Nesbitt FL, Tardy DC. Rate constant and RRKM product study for the reaction between CH3 and C2H3 at T = 298 K. INT J CHEM KINET 2000. [DOI: 10.1002/(sici)1097-4601(2000)32:5<304::aid-kin6>3.0.co;2-j] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Nesbitt FL, Thorn RP, Payne WA, Tardy DC. Absolute Rate Constant and Product Branching Fractions for the Reaction between F and C2H4 at T = 202−298 K. J Phys Chem A 1999. [DOI: 10.1021/jp9901747] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fred L. Nesbitt
- Department of Natural Sciences, Coppin State College, Baltimore, Maryland 21216
| | - R. Peyton Thorn
- Laboratory for Extraterrestrial Physics, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771
| | - Walter A. Payne
- Laboratory for Extraterrestrial Physics, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771
| | - D. C. Tardy
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242
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Hoobler RJ, Leone SR. Rate coefficients for reactions of ethynyl radical (C2H) with HCN and CH3CN: Implications for the formation of complex nitriles on Titan. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/97je02526] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Clarke DW, Ferris JP. Titan haze: structure and properties of cyanoacetylene and cyanoacetylene-acetylene photopolymers. ICARUS 1997; 127:158-172. [PMID: 11541127 DOI: 10.1006/icar.1996.5667] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The structure and morphological properties of polymers produced photochemically from the UV irradiation of cyanoacetylene and cyanoacetylene mixtures have been examined to evaluate their possible contribution to the haze layers found on Titan. A structural analysis of these polymers may contribute to our understanding of the data returned from the Huygens probe of the Cassini mission that will pass through the atmosphere of Titan in the year 2004. Infrared analysis, elemental analysis, and thermal methods (thermogravimetric analysis, thermolysis, pyrolysis) were used to examine structures of polycyanoacetylenes produced by irradiation of the gas phase HC3N at 185 and 254 nm. The resulting brown to black polymer, which exists as small particles, is believed to be a branched chain of conjugated carbon-carbon double bonds, which, on exposure to heat, cyclizes to form a graphitic structure. Similar methods of analysis were used to show that when HC3N is photolyzed in the presence of Titan's other atmospheric constituents (CH4, C2H6, C2H2, and CO), a copolymer is formed in which the added gases are incorporated as substituents on the polymer chain. Of special significance is the copolymer of HC3N and acetylene (C2H2). Even in experiments where C2H2 was absorbing nearly all of the incident photons, the ratio of C2H2 to HC3N found in the resulting polymer was only 2:1. Scanning electron microscopy was used to visually examine the polymer particles. While pure polyacetylene particles are amorphous spheres roughly 1 micrometer in diameter, polycyanoacetylenes appear to be strands of rough, solid particles slightly smaller in size. The copolymer of HC3N and C2H2 exhibits characteristics of both pure polymers. This is particularly important as pure polyacetylenes do not match the optical constants measured for Titan's atmospheric hazes. The copolymers produced by the incorporation of other minor atmospheric constituents, like HC3N, into the polyacetylenes are expected to have optical constants more comparable to those of the Titan haze.
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Affiliation(s)
- D W Clarke
- Department of Chemistry, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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Lara LM, Lellouch E, López-Moreno JJ, Rodrigo R. Vertical distribution of Titan's atmospheric neutral constituents. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/96je02036] [Citation(s) in RCA: 261] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Thorn RP, Payne WA, Stief LJ, Tardy DC. Rate Constant and Product Branching for the Vinyl Radical Self Reaction at T = 298 K. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960825o] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. P. Thorn
- Laboratory for Extraterrestrial Physics, Code 691, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771
| | - W. A. Payne
- Laboratory for Extraterrestrial Physics, Code 691, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771
| | - L. J. Stief
- Laboratory for Extraterrestrial Physics, Code 691, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771
| | - D. C. Tardy
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242
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Clarke DW, Ferris JP. Mechanism of cyanoacetylene photochemistry at 185 and 254 nm. JOURNAL OF GEOPHYSICAL RESEARCH 1996; 101:7575-84. [PMID: 11539381 DOI: 10.1029/95je03649] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The role of cyanoacetylene (HC3N) in the atmospheric photochemistry of Titan and its relevance to polymer formation are discussed. Investigation of the relative light absorption of HC3N, acetylene (C2H2), and diacetylene (C4H2) revealed that HC3N is an important absorber of UV light in the 205- to 225-nanometer wavelength region in Titan's polar regions. Laboratory studies established that photolysis of C2H2 initiates the polymerization of HC3N even though the HC3N is not absorbing the UV light. Quantum yield measurements establish that HC3N is 2-5 times as reactive as C2H2 for polymer formation. Photolysis of HC3N with 185-nanometer light in the presence of N2, H2, Ar, or CF4 results in a decrease in the yield of 1,3,5-tricyanobenzene (1,3,5-tcb), while photolysis in the presence of CH4, C2H6, or n-C4H10 results in an increase in 1,3,5-tcb. The rate of loss of HC3N is increased by all gases except H2, where it is unchanged. It was not possible to detect 1,3,5-tcb as a photoproduct when the partial pressure of HC3N was decreased to 1 torr. Photolysis of HC3N with 254-nanometer light in the presence of H2 or N2 results in the formation of 1,2,4-tcb, while photolysis in the presence of CH4, C2H6, or n-C4H10 results in the formation of increasing amounts of 1,3,5-tcb. Mechanisms for the formation of polymers are presented.
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Affiliation(s)
- D W Clarke
- Department of Chemistry, Rensselaer Polytechnic Institute, Troy, New York, USA
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Krasnopolsky VA, Cruikshank DP. Photochemistry of Triton's atmosphere and ionosphere. JOURNAL OF GEOPHYSICAL RESEARCH 1995; 100:21271-86. [PMID: 11541126 DOI: 10.1029/95je01904] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The photochemistry of 32 neutral and 21 ion species in Triton's atmosphere is considered. Parent species N2, CH4, and CO (with a mixing ratio of 3 x 10(-4) in our basic model) sublime from the ice with rates of 40, 208, and 0.3 g/cm2/b.y., respectively. Chemistry below 50 km is driven mostly by photolysis of methane by the solar and interstellar medium Lyman-alpha photons, producing hydrocarbons C2H4, C2H6, and C2H2 which form haze particles with precipitation rates of 135, 28, and 1.3 g/cm2/b.y., respectively. Some processes are discussed which increase the production of HCN (by an order of magnitude to a value of 29 g/cm2/b.y.) and involve indirect photolysis of N2 by neutrals. Reanalysis of the measured methane profiles gives an eddy diffusion coefficient K = 4 x 10(3) cm2/s above the tropopause and a more accurate methane number density near the surface, (3.1 +/- 0.8) x 10(11) cm-3. Chemistry above 200 km is driven by the solar EUV radiation (lambda < 1000 angstroms) and by precipitation of magnetospheric electrons with a total energy input of 10(8) W (based on thermal balance calculations). The most abundant photochemical species are N, H2, H, O, and C. They escape with the total rates of 7.7 x 10(24) s-1, 4.5 x 10(25) s-1, 2.4 x 10(25) s-1, 4.4 x 10(22) s-1, and 1.1 x 10(24) s-1, respectively. Atomic species are transported to a region of 50-200 km and drive the chemistry there. Ionospheric chemistry explains the formation of an E region at 150-240 km with HCO+ as a major ion, and of an F region above 240 km with a peak at 320 km and C+ as a major ion. The ionosphere above 500 km consists of almost equal densities of C+ and N+ ions. The model profiles agree with the measured atomic nitrogen and electron density profiles. A number of other models with varying rate coefficients of some reactions, differing properties of the haze particles (chemically passive or active), etc., were developed. These models show that there are four basic unknown values which have strong impacts on the composition and structure of the atmosphere and ionosphere. These values and their plausible ranges are the CO mixing ratio fco = 10(-4)-10(-3), the magnetospheric electron energy input (1 +/- 0.5) x 10(8) W, the rate coefficient of charge-exchange reaction N2(+) + C k = 10(-11)-10(-10) cm3/s, and the ion escape velocity Vi approximately equal to 150 cm/s.
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Affiliation(s)
- V A Krasnopolsky
- National Research Council/NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
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