The Dynamic Response at the Surface of Simple Metals

本研究的目的是测量（并随后解释）简单金属表面的电子和原子对时变扰动的动态响应。理解表面的动力响应无疑是表面科学中最具挑战性的基本问题之一，因为它需要一个表面激励模式的定量图像。另一方面，表面的动态响应与表面的许多物理和化学性质密切相关，如能量传递（激发态和粘着系数的寿命），范德华力，光产率，线性和非线性光学性质，以及表面等离子体色散。光电发射、非弹性电子散射和非线性光学将用于测量表面电子的线性和非线性响应。动量分解非弹性电子散射将被用来确定表面声子色散。通过研究激发光谱从单个吸收的碱金属原子到薄膜、再到厚膜的演变，以及使用碱金属簇源的簇大小的函数，研究降低问题维数对动力学响应的影响。碱团簇动力学响应的研究是本课题研究的新方向。

The objective of this research is to measure (and subsequently explain) the dynamic response of the electrons and atoms at the surface of a simple metal to a time varying disturbance. Understanding the dynamical response of a surface is surely one of the most challenging fundamental problems in surface science, since it requires a quantitative picture of excitation modes at a surface. On the other hand, the dynamic response of the surface is intimately related to many physical and chemical properties of the surface, such as energy transfer (lifetimes of excited states and sticking coefficients), van der Waals forces, photoyield, both linear and nonlinear optical properties, as well as surface plasmon dispersion. Photoemission, inelastic electron scattering and nonlinear optics will be used to measure both the linear and nonlinear response of the elctrons at the surface. Momentum resolved inelastic electron scatteirng will be utilized to determine the surface phonon dispersion. The effect on the dynamical response due to reducing the dimensionality of the problem will be investigated by studying the evolution of the excitation spectra from a single absorbed alkali atom, to thin films, to thick films, as well as a function of cluster size using an alkali metal cluster source. The investigation of dynamical response in alkali clusters is a new direction for this research program.