The Dynamic Response at the Surface of Simple Metals

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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.