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Author Kobayashi, Hitomi ♦ Kawakita, Hideyo ♦ Hidaka, Hiroshi ♦ Hama, Tetsuya ♦ Watanabe, Naoki ♦ Lamberts, Thanja ♦ Kästner, Johannes
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY ♦ ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ ADSORPTION ♦ AMORPHOUS STATE ♦ CARBON MONOXIDE ♦ DEUTERATION ♦ HYDROCARBONS ♦ HYDROGENATION ♦ ICE ♦ MOLECULES ♦ SIMULATION ♦ SPACE ♦ TEMPERATURE RANGE 0013-0065 K ♦ TUNNEL EFFECT
Abstract We quantitatively investigated the hydrogen addition reactions of acetylene (C{sub 2}H{sub 2}) and ethylene (C{sub 2}H{sub 4}) on amorphous solid water (ASW) at 10 and 20 K relevant to the formation of ethane (C{sub 2}H{sub 6}) on interstellar icy grains. We found that the ASW surface enhances the reaction rates for C{sub 2}H{sub 2} and C{sub 2}H{sub 4} by approximately a factor of 2 compared to those on the pure-solid C{sub 2}H{sub 2} and C{sub 2}H{sub 4} at 10 K, probably due to an increase in the sticking coefficient and adsorption energy of the H atoms on ASW. In contrast to the previous proposal that the hydrogenation rate of C{sub 2}H{sub 4} is orders of magnitude larger than that of C{sub 2}H{sub 2}, the present results show that the difference in hydrogenation rates of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} is only within a factor of 3 on both the surfaces of pure solids and ASW. In addition, we found the small kinetic isotope effect for hydrogenation/deuteration of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} at 10 K, despite the requirement of quantum tunneling. At 20 K, the reaction rate of deuteration becomes even larger than that of hydrogenation. These unusual isotope effects might originate from a slightly larger number density of D atoms than H atoms on ASW at 20 K. The hydrogenation of C{sub 2}H{sub 2} is four times faster than CO hydrogenation and can produce C{sub 2}H{sub 6} efficiently through C{sub 2}H{sub 4} even in the environment of a dark molecular cloud.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2017-03-10
Publisher Place United States
Journal Astrophysical Journal
Volume Number 837
Issue Number 2


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