Surface Electronic Excitation and Elementary Process in Reaction

表面原子和电子结构研究的实验和理论方法已经建立并应用于各种系统。热平衡下的表面反应的实验研究也已广泛开展。与这些方法相比，我们试图发展新的方法来研究表面动力学现象，通过电子激发和非平衡条件下的实验和理论合作，通过价电子激发的光刺激表面反应被认为是有效的解释金属催化剂的催化活性，因为观察到高选择性，并且通过避免电子激发态和基态之间的交叉而产生基元反应中的过渡态。另一种方法是使用非平衡分子束如定向分子束和自旋极化原子束的基元反应。从理论上讲，必须处理与电子激发态和电子间强关联有关的复杂系统。本课题对这些研究进行了深入的探讨，提出了NO分子在Pt（111）表面的脱附速率对激光诱导脱附中间激发态寿命的影响，并给出了中间激发态的势能面。本文从理论上研究了价电子激发引起的光刺激脱附机理。研究发现，CH_4在Pt（111）表面上的激光诱导分解具有明显的特征。在非平衡束流中，利用激光抽运的方法产生了Cs原子的自旋极化束流，并成功地对散射H_2分子进行了共振增强多光子电离探测，用于研究o-H_2束流在表面上的邻-对位转换。

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.