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Date of Award
The recent years have seen a lot of progress in the state-of-the-art of tools and techniques utilized in probing electron dynamics of small molecules, surfaces, and large chemical systems. These tools and techniques have also been widely used to study many interesting phenomena, as well as determining important physical parameters like the carrier envelope phase (CEP) of ultrashort pulses. Most of these studies have broad applications in fields like atmospheric and interstellar chemistry, combustion chemistry, and biology. 3D momentum imaging remains one of the most versatile and major technique employed in most of these studies. This dissertation highlights a recent application involving the use of 3D momentum imaging in probing electronic dynamics of surfaces in a study where an event driven camera (Tpx3Cam) and a high-speed digitizer were used to detect the 2D positions of electrons and TOF information (∼30 ps) respectively, for each event at a rate approaching 1 Mhits/sec.
In the few-cycle pulse regime, the waveform of the electric field of laser pulses changes drastically with change in CEP. Making the measurement of this important parameter very crucial in many relevant fields. Although there are a myriad of techniques available to measure the CEP of ultrashort pulses, one common technical issue associated with most of these techniques is the difficulty in measuring the absolute CEPs directly. Here in this work, we developed a novel in-situ technique based on angular which directly measure the absolute CEPs of few-cycle elliptically polarized laser pulses. The estimated precision of this single-shot measurements was 0.19 radians. This newly developed technique was used to accurately measure the absolute CEPs of few-cycle linearly polarized laser pulses in a strong field ionization of Ar. A comparison between experimental and theory results on absolute phase resolved strong field ionization suggests that TDSE and SAE without the inclusion of core polarization is not sufficient for accurately modeling of strong field ionization processes even in noble gas atoms. This result will provide a clear benchmark for future theoretical models in strong field ionization processes involving multielectron species.
Debrah, Duke Asante, "Absolute Phase Resolved Strong Field Ionization Probed By 3d Momentum Imaging" (2022). Wayne State University Dissertations. 3594.