Quantum Dynamics of Abstraction in H(g)+H(a)/Cu(111) : Direct (Eley-Rideal) and Indirect (Hot-Atom) Processes

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We investigate and discuss the dynamics of H abstraction from Cu(111) by performing quantum dynamics calculations. We introduce a new theoretical approach that considers both quantum mechanically direct (the impinging H directly abstracts an adsorbed H) and indirect (the impinging H diffuses across the surface before it abstracts an adsorbed H) processes for H abstraction, and investigate how the coverage of adsorbed H on Cu(111) affects the vibrational and surface-parallel translational energy distribution of product H_2. We expect that the H abstraction dynamics would depend on the coverage, because the shape of the corrugation depends on the coverage. Our results, for the case when the kinetic energy of the incident H E_t=0.1eV, confirm this expectation. The mean vibrational energies of product HI decrease with-decreasing coverage. On the other hand, the mean surface-parallel translation energies of product H_2 increase with decreasing coverage. These results indicate that for the low coverage case, H abstraction occurs mainly through the indirect process, where the vibrational excitation of product Ha is suppressed, and the excitation for the surface-parallel translational motion of product HT is enhanced, as compared with those for the high coverage case, where the H abstraction can occur through both direct and indirect processes.
社団法人日本物理学会の論文
2002-01-15