On the encounter desorption of hydrogen atoms on an ice mantle

At low temperatures (∼10 K), hydrogen atoms can diffuse quickly on grain ice mantles and frequently encounter hydrogen molecules, which cover a notable fraction of grain surface. The desorption energy of H atoms on H 2 substrates is much less than that on water ice. The H atom encounter desorption m...

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Bibliographic Details
Published in:Research in astronomy and astrophysics 2021-03, Vol.21 (2), p.39-120
Main Authors: Chang, Qiang, Zheng, Xu-Li, Zhang, Xia, Quan, Dong-Hui, Lu, Yang, Meng, Qing-Kuan, Li, Xiao-Hu, Chen, Long-Fei
Format: Article
Language:English
Subjects:
Abundance
Chemical bonds
Desorption
Diffusion
Hydrogen
Hydrogen atoms
Ice
Low temperature
Monte Carlo simulation
Substrates
Water ice
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Summary:At low temperatures (∼10 K), hydrogen atoms can diffuse quickly on grain ice mantles and frequently encounter hydrogen molecules, which cover a notable fraction of grain surface. The desorption energy of H atoms on H 2 substrates is much less than that on water ice. The H atom encounter desorption mechanism is adopted to study the enhanced desorption of H atoms on H 2 substrates. Using a small reaction network, we show that the steady-state surface H abundances predicted by the rate equation model that includes H atom encounter desorption agree reasonably well with the results from the more rigorous microscopic Monte Carlo method. For a full gas-grain model, H atom encounter desorption can reduce surface H abundances. Therefore, if a model adopts the encounter desorption of H atoms, it becomes more difficult for hydrogenation products such as methanol to form, but it is easier for C, O and N atoms to bond with each other on grain surfaces.
ISSN:1674-4527
DOI:10.1088/1674-4527/21/2/39