Measurements of Energy Partitioning in H2 Formation by Photolysis of Amorphous Water Ice
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Authors
Yabushita, Akihiro
Hama, Tetsuya
Lida, Daisuke
Kawanaka, Noboru
Kawasaki, Masahiro
Watanabe, Naoki
Ashfold, Michael N. R.
Loock, Hans-Peter
Date
2016-03-21
Type
journal article
Language
en
Keyword
Dust , Extinction-ISM , Molecules , Molecular Data , Molecular Processes , Ultraviolet: ISM
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Abstract
We demonstrate experimentally that photodissociation of amorphous solid water at 100 K results in formation of H2 molecules with an ortho/para ratio of gOPR = 3. Two distinct mechanisms can be identified: endothermic abstraction of a hydrogen atom from H2O by a photolytically produced H atom yields vibrationally cold H2 products, whereas exothermic recombination of two H-atom photoproducts yields translationally and internally hot H2. These results are in accord with predictions by molecular dynamics calculations and their astrophysical implications are discussed.
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ISSN
0004-637X