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Title: THERMAL REACTIONS OF OXYGEN ATOMS WITH ALKENES AT LOW TEMPERATURES ON INTERSTELLAR DUST

Laboratory experiments show that the thermal heterogeneous reactions of oxygen atoms may contribute to the synthesis of epoxides in interstellar clouds. The data set also indicates that the contribution of these pathways to epoxide formation, in comparison to non-thermal routes, is likely to be strongly temperature dependent. Our results indicate that an increased abundance of epoxides, relative to the corresponding aldehydes, could be an observational signature of a significant contribution to molecular oxidation via thermal O atom reactions with alkenes. Specifically surface science experiments show that both C{sub 2}H{sub 4}O and C{sub 3}H{sub 6}O are readily formed from reactions of ethene and propene molecules with thermalized oxygen atoms at temperatures in the range of 12-90 K. It is clear from our experiments that these reactions, on a graphite surface, proceed with significantly reduced reaction barriers compared with those operating in the gas phase. For both the C{sub 2}H{sub 4} + O and the C{sub 3}H{sub 6} + O reactions, the surface reaction barriers we determine are reduced by approximately an order of magnitude compared with the barriers in the gas phase. The modeling of our experimental results, which determines these reaction barriers, also extracts desorption energies and rate coefficients formore » the title reactions. Our results clearly show that the major product from the O + C{sub 2}H{sub 4} reaction is ethylene oxide, an epoxide.« less
Authors:
;  [1]
  1. Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)
Publication Date:
OSTI Identifier:
21612676
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 741; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/741/2/121; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ACETALDEHYDE; ACETONE; ASTROPHYSICS; DESORPTION; DUSTS; EPOXIDES; ETHYLENE; GRAPHITE; INTERSTELLAR GRAINS; INTERSTELLAR SPACE; OXIDATION; OXIDES; OXYGEN; PROPYLENE; TEMPERATURE DEPENDENCE ALDEHYDES; ALKENES; CARBON; CHALCOGENIDES; CHEMICAL REACTIONS; ELEMENTS; HYDROCARBONS; KETONES; MINERALS; NONMETALS; ORGANIC COMPOUNDS; ORGANIC OXYGEN COMPOUNDS; OXYGEN COMPOUNDS; PARTICLES; PHYSICS; SORPTION; SPACE