Theoretical Study for Dynamics of Molecules near Metal Surfaces

为了阐明分子在金属表面的反应性，有必要建立与电子系统的基态能量和激发态能量相对应的势能面(PES)以及激发态的驰豫机制的准确知识。从这个角度出发，对分子在金属表面的反应性进行了理论研究。主要研究结果如下：1.通过对双原子分子在金属表面的散射动力学实验结果和计算结果的比较，阐明了NO/Ag(111)双原子分子的PES随分子轴取向的变化规律。2.在金属表面分子散射的分子内振动激发过程中，电子系统向分子内振动自由度的能量传递起着重要的作用，即非绝热效应。3.C-…分子内振动的瞬时吸收差谱分析阐明了最近用超短脉冲激光在铂(111)面上观察到的更多的氧、振动态与谐振态的偏离以及金属表面激发振动态的驰豫时间。4.提出了一种新的光激发脱附模型，该模型从微观角度考虑了电子体系的自由度和吸附分子的平移运动之间的耦合。通过对模型计算结果与实验结果的比较，验证了新模型的有效性。5.H_2/Cu体系的解离吸附是一种活化过程。旋转激发对解离吸附有两种影响，即转向效应和能量传递效应。前者在低转动能区占主导地位，后者在高能区占优势。结果表明，粘滞几率对转动激发的依赖关系不是单调的。较少

In order to clarify the reactivity of molecules at metal surfaces, it is necessary to build up accurate knowledge of potential energy surfaces (PES) corresponding to the ground state energy and excited state energy of electron system, and relaxation mechanism of excited states. From this view, theoretical study has been done on the reactivity of molecules at metal surfaces. The obtained results are summarized as follows.1.On the basis of comparison between experimental and calculational results for scattering dynamics of diatomic molecules from metal surfaces, the dependence of PES on orientation of molecular axis has been clarfied for NO/Ag (111). 2. In the excitation process of intramolecular vibration in the scattering of molecules from metal surfaces, energy transfer from electron system to intramolecular vibrational degree of freedom, i.e., non-adiabatic effect plays an improtant role. 3. On the analysis of transient absorption difference spectra for intra-molecular vibration of C … More O on Pt (111) observed recently by the use of ultrashort-pulse laser, deviation of vibrational states from harmonicity and relaxation time of excited vibrational states at metal surfaces are clarified. 4. A new model is proposed for photo-stimulated desorption, in which the coupling between degrees of freedom of electron system and translational motion of adsorbates is taken into account from a microscopic viewpoint. On the basis of the comparison between model calculations and the experimental results for desorption probability, the validity of the proposed new model is clarified. 5. Dissociative adsorption in H2/Cu system is a paradigm of activated processes. There are two kinds of effects of rotational excitation on the dissociative adsorption, i.e., steering effect and energy transfer effect. The former is dominant for low rotational energy region and the latter for high energy region. As a result, non-monotonous dependendce of sticking probability on rotational excitation can be observed. Less