| 研究実績の概要 |
This year, the hydrogen molecule's (H2) rotational state in a nanojunction has been investigated by means of model Hamiltonian calculations. We extended the formulations to account for both the effects of the environment which was represented by a phonon bath and the molecular vibration. The walls of the nanojunction were modeled by an infinite metal surface and the interaction with H2 has been considered using a phenomenological Hamiltonian. Using this simplified model, we derived the orientation-dependent charge exchange and the electronic friction coefficient of the scattering H2. Both charge exchange and electronic friction were found to be highly anisotropic and dependent on the coupling with the environment. We found that the occupation probability after scattering is higher for perpendicular than parallel oriented H2. From the friction coefficient we obtained the average energy dissipated into the excitation of electron-hole in the metal and eventually the sticking probability. Within our chosen parameters, we found that the magnitude of the friction coefficient of H2 oriented perpendicular to the surface is larger than the one oriented parallel. This entails that the former has the larger probability of being adsorbed. Our results have important implications not just in hydrogen storage but also in other fields such as electrocatalysis.
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