There are two proposed mechanisms through which molecular hydrogen is thought to form at the dust grain surfaces: the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism. One of the problems associated with this project is to determine which (if either) of the two mechanisms is dominant in space. Also, we need to know if the vibrational population of the molecules produced by the two mechanisms is different, since this will affect the theoretical models of the process.
The two mechanisms are described pictorially below:
Eley-Rideal Mechanism
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An atom adsorbs onto the surface. |
Another atom passes by which interacts with the one on the surface. |
A molecule is formed which desorbs. |
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Two atoms adsorb onto the surface. |
They diffuse across the surface and interact when they are close. |
A molecule is formed which desorbs. |
