Surface Electronic Excitation and Elementary Process in Reaction

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Experimental and theoretical methods of the surface atomic and electronic structure studies have been established and applied to various systems. Experimental studies on surface reactions at the thermal equilibrium have slso extensively been carried out. In contrast to these methods, we have tried to develope novel methods for studying surface dynamical phenomena via the electronic excitation and under the non-equlibrium conditions in collaboration with experiment and theory.The photostimulated surface reaction via the valence electron excitation is considered to be effective for elucidating the catalytic activity of metal catalysts, since the high selectivity was observed and the transition state in the elementary reaction is generated by the avoided crossing between the electronically excited and the ground state. Another approach is elementary reaction using non-equilibrium molecular beams such as an oriented molecular beam and spin-polarized atomic beam. From the theoretical standpoint, the complex system concerned with the elctronically excited states and the strong correlation between electrons must be treated. These researches have been developed and discussed in this research project.The lifetime of the intermediate excited state in laser-induced desorption depends on the velocity of desorbed NO molecules from Pt (111), and the potential energy surface at the intermediate excited state has been proposed. The mechanism of photostimulated desorption induced by valence electron excitation has been theoretically studied. Laser-induced decomposition of CH_4 chemisorbed on Pt (111) was found to show a characteristic feature. In the non-equilibrium beam, the spin-polarized atomic beam of Cs has been developed using the laser pump method and the resonance enhanced multiphoton ionization detection of scattered H_2 molecules has been succeded for the study of ortho-para conversion of the o-H_2 beam on the surface.