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Laser-Assisted Dynamics on Metallic Surfaces using Ultrafast X-Rays

TitleLaser-Assisted Dynamics on Metallic Surfaces using Ultrafast X-Rays
Publication TypeThesis
Year of Publication2009
AuthorsMiaja-Avila, L
Abstract

Time-resolved photoelectron spectroscopy is a powerful technique for the study of real-time electron dynamics on metallic surfaces. These studies are performed in pump- probe geometries, where a pump pulse excites a dynamic process and a time-delayed probe monitors changes in the system. Furthermore, recent progress in ultrafast lasers and high-harmonic generation has opened up a new area of surface science, where these two light sources are the standard tools for the study of ultrafast surface dynamics. An- other critical discovery that has made it possible to study high-energy and femtosecond time-scale atomic dynamics is the laser-assisted photoelectric effect. However, until 2005 this effect had only been observed in gas-phase atomic systems, limiting its applicability to the study of isolated atoms or molecules.

Using time-resolved photoelectron spectroscopy, this thesis presents work demon- strating that the physics of the laser-assisted photoelectric effect can be expanded to solid-state systems. This result represents the laser-assisted version of the original man- ifestation of the photoelectric effect. This thesis also presents experimental data show- ing that laser-assisted photoemission from surfaces can be distinguished from other laser-surface interaction phenomena, such as hot electron excitation, above-threshold photoemission, and space-charge acceleration.

Additionally, by using surface laser-assisted photoemission and laser-assisted Auger decay, a direct measurement of the lifetime of core-excited states of an atom adsorbed onto a surface is presented. Finally, this research demonstrates that using a dressing laser at longer wavelengths dramatically reduces above-threshold photoemission and space-charge effects while enhancing the surface laser-assisted photoemission signal.