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Attosecond Light Pulses and Attosecond Electron Dynamics Probed using Angle-Resolved Photoelectron Spectroscopy

TitleAttosecond Light Pulses and Attosecond Electron Dynamics Probed using Angle-Resolved Photoelectron Spectroscopy
Publication TypeThesis
Year of Publication2017
AuthorsChen, C
Academic DepartmentPhysics
DegreePh.D.
Number of Pages269
Date Published2017-06
UniversityUniversity of Colorado
CityBoulder, CO
Abstract

Recent advances in the generation and control of attosecond light pulses have opened up new opportunities for the real-time observation of sub-femtosecond (1 fs = 10-15 s) electron dynamics in gases and solids. Combining attosecond light pulses with angle-resolved photoelectron spectroscopy (atto-ARPES) provides a powerful new technique to study the influence of material band structure on attosecond electron dynamics in materials. Electron dynamics that are only now accessible include the lifetime of far-above-bandgap excited electronic states as well as fundamental electron interactions such as scattering and screening. In addition, the same atto-ARPES technique can also be used to measure the temporal structure of complex coherent light fields. In this thesis, I present four experiments utilizing atto-ARPES to provide new insights into the generation and characterization of attosecond light pulses as well as the attosecond electron dynamics in transition metals. First, I describe a new method to extend attosecond metrology techniques to the reconstruction of circularly polarized attosecond light pulses for the first time. Second, I show that by driving high harmonics with a two-color linearly polarized laser field, quasi-isolated attosecond pulses are generated because the phase-matching window is confined. Third, I present the first measurement of lifetimes for photoelectrons that are born into free-electron-like states compared with those that are excited into unoccupied excited states in the band structure of a material (Ni(111)). The finite excited-state lifetime causes a ≈200 as delay in the emission of photoelectrons. Finally, I describe direct time-domain studies of  electron-electron interactions in transition metals with both simple and complex Fermi surfaces. In particular, I show the influence of electron-electron scattering and screening on the lifetime of photoelectrons.