| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The main aim in the first year was to understand the process of formation of surface phonons in collisions of a surface with low-energy atoms or ions, and of the decay of the surface phonons. The potential energy surfaces (PES) for the He atom (the HeィイD1+ィエD1 ion) impinging on the Ni (or CU) surface were calculated. The cross section for charge transfer at incident energies E of 10 meV to 1 eV was calculated as a model case and was found to be as large as 10ィイD1-16ィエD1 cmィイD12ィエD1. In the next year, the main objective was the study of the adsorption of molecules on a solid surface and the dissipation of the vibrational excitation energy to the solid. In the molecular collisions at several eV, the translation-vibration interaction and the molecular vibration-surface phonon interaction were the main interactions. There are two kinds of adsorption, "molecular adsorption" in which the molecules do not dissociate, and "dissociative adsorption" in which the molecules dissociate into fragmen
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ts after adsorption. To understand the molecular adsorption mechanism in detail, we used the molecule-surface PES calculated in the first year and the quantum mechanical close-coupling method for the dynamics. The last year was devoted to the study of energy exchange in collisions of HィイD22ィエD2 and OィイD22ィエD2 with Ni, Cu, and Fe surfaces by using a semiclassical simulation method. The parameters we changed are E (0.1-10 eV), rotational-vibrational quantum numbers (v, J), and the surface temperature. The results obtained about the adsorption, energy transfer, and energy dissipation processes are: (I) At E<1 eV, HィイD22ィエD2 in the ground (v, J) state collide with the surface and are adsorbed after hopping on the surface several times. For highly excited (v=5-10, J=10-29) HィイD22ィエD2, they hop more often than for the ground-state HィイD22ィエD2 and can be adsorbed eventually. The energy dissipation occurs after a considerable amount of time after the collision. (ii) At E<1 eV, OィイD22ィエD2 in the ground (v, J) state collide with the surface and are adsorbed after hopping on the surface several times. The number of hopping, however, is less than for HィイD22ィエD2. Some molecules are dissociated depending on their orientation at the time of the collision. The energy dissipation is a slow process in this case too. For surfaces with heavy atoms, the phonon energy sometimes localizes on the surface without dissipation into the second layer or deeper. Less
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