Long-Time Scale Simulations of Tunneling-Assisted Diffusion of Hydrogen on Ice Surfaces at Low Temperature
| Autor: | Hannes Jónsson, Kjartan Thor Wikfeldt, Vilhjálmur Ásgeirsson |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Hydrogen
Chemistry Interstellar cloud Ice Ih chemistry.chemical_element Atmospheric temperature range 01 natural sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Amorphous solid General Energy Chemical physics 0103 physical sciences Amorphous ice Astrophysics::Earth and Planetary Astrophysics Kinetic Monte Carlo Physical and Theoretical Chemistry Atomic physics Diffusion (business) 010306 general physics 010303 astronomy & astrophysics |
| Zdroj: | The Journal of Physical Chemistry C. 121:1648-1657 |
| ISSN: | 1932-7455 1932-7447 |
| DOI: | 10.1021/acs.jpcc.6b10636 |
| Popis: | Hydrogen (H) atom diffusion on dust grain surfaces is the rate-limiting step in many hydrogenation reactions taking place in interstellar clouds. In cold (10–30 K) molecular clouds, the dust grains are coated by amorphous water ice. Therefore, H adatom mobility on ice surfaces is of fundamental importance in this context. We have calculated H atom adsorption and diffusion on both crystalline and amorphous ice surfaces using an analytic interaction potential for H2O–H. Tunneling rates for H atom hops between adsorption sites are explicitly calculated, the kinetic Monte Carlo method is used to simulate long time scale evolution and the diffusion coefficient, D, is evaluated for the temperature range 5–120 K. For ice Ih, we find D = 1.6 × 10–7 cm2/s at 10 K and below that temperature tunneling becomes the dominant diffusion mechanism. On the amorphous ice surface, the mobility of H is much slower than for ice Ih, D = 5.8 × 10–11 cm2/s at 25 K. Below 25 K, the H adatom becomes trapped in the deepest adsorptio... |
| Databáze: | OpenAIRE |
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