2024-03-29T11:47:16Zhttps://uvadoc.uva.es/oai/requestoai:uvadoc.uva.es:10324/428042021-06-23T11:56:22Zcom_10324_1186com_10324_931com_10324_894col_10324_1404
Reconstruction of water ice: the neglected process OH + OH → H2O + O
Redondo Cristóbal, María del Pilar
Pauzat, F.
Ellinger, Y.
Markovits, A.
Astroquímica
Astrochemistry
21 Astronomía y Astrofísica
Producción Científica
Context. Although H2O is the most important molecular material found in the solid state in the interstellar medium, the chemical routes leading to ice through surface reactions are still a matter of discussion. Three reaction pathways proposed in the past are at the heart of current research: hydrogenation of atomic oxygen, molecular oxygen, and ozone. The reaction network finally leads to a small number of processes giving H2O: H + OH, H2 + OH, and H + H2O2. To these processes, OH + OH should be added. It is known to be efficient in atmospheric chemistry and takes the irradiations of the interstellar grains into account that, directly or indirectly, create a number of OH radicals on and in the icy mantles.
Aims. We study the role of the existing ice in its own reconstruction after it is destroyed by the constant irradiation of interstellar grains and focus on the OH + OH reaction in the triplet state.
Methods. We used numerical simulations with a high level of coupled cluster ab initio calculations for small water aggregates and methods relevant to density functional theory for extended systems, including a periodic description in the case of solid water of infinite dimensions.
Results. OH + OH → H2O + O reaction profiles are reported that take the involvement of an increasing number of H2O support molecules into account. It is found that the top of the barrier opposing the reaction gradually decreases with the number of supporting H2O and falls below the level of the reactants for H2O layers or solid water.
Conclusions. In contrast to the gas phase, the reaction is barrierless on water ice. By adding a reconstructed H2O molecule and a free oxygen atom at the surface of the remaining ice, this reaction leaves open the possibility of the ice reconstruction.
2020-10-07T08:48:12Z
2020-10-07T08:48:12Z
2020
info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
https://doi.org/10.1051/0004-6361/202037771
Astronomy and Astrophysics, Volume 638, June 2020, A125
0004-6361
http://uvadoc.uva.es/handle/10324/42804
A125
Astronomy & Astrophysics
638
1432-0746
eng
https://www.aanda.org/articles/aa/abs/2020/06/aa37771-20/aa37771-20.html
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2020 The Authors
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