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Access Type
WSU Access
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Chemistry
First Advisor
Wen Li
Abstract
All chemical, biological, and physical reactions are driven by the correlated motions of electrons and their interaction with their parent ions. Probing and capturing the dynamics of the correlations of electrons and ions will reveal the details of the fundamental mechanism at which certain reactions occur which tends to be difficult to probe in the world of traditional chemistry. This will also provide chemists with deeper insights on how to control and optimize chemical reactions. However, the dynamics of electrons and ions happen at an ultrashort timescale within the femtosecond and attosecond time range. Several techniques have been developed in the past to capture these dynamics in their natural timescale and one of such techniques is the 3D velocity map imaging.This thesis describes in detail the development, implementation, and validation of the 3D velocity map imaging technique for the imaging of the momentum distribution of electrons and ions produced from the strong field ionization of atoms and molecules using an ultrafast laser system. An all-optical imaging technique that employs the use of a fast scintillator screen and a SiPMT was implemented for the 3D imaging of electrons. With this technique, we were able to detect two electrons in coincidence with the shortest possible deadtime of ~0.48ns. We also developed a new two-camera imaging system which serves as an alternative and cost-effective method for performing 3D momentum imaging of particles without the need for specialized timing equipment. This new technique can detect and resolve two ions with different masses and can achieve a temporal resolution of 2 ns when detecting photoelectrons. It can also be operated at a higher count which makes it a suitable approach to perform covariance imaging experiments. While the 3D momentum imaging technique is a powerful tool for probing electron and ion dynamics, the carrier-envelope phase (CEP) is also an important parameter to consider when probing electron dynamics using few-cycle laser pulses. Previously, the Li group has developed a way for directly measuring the CEP using the attoclock (angular streaking) technique. In this thesis, we demonstrate for the first time how we can exploit the CEP effect to measure the deflection angle of electrons for circularly polarized light using the phase-resolved attoclock technique. With this technique, we were able to investigate the nonadiabatic motion of electrons under the tunneling barrier and the effect of the coulomb potential on the deflection angle of the electron. Our result reveals that the coulomb potential dominates the dynamic motion of the electrons while nonadiabaticity and tunneling delay plays a minor role.
Recommended Citation
Orunesajo, Emmanuel, "Ultrafast Imaging Of Electrons And Ions In Strong-Field Ionization Using Few-Cycle Laser Pulses" (2024). Wayne State University Dissertations. 4104.
https://digitalcommons.wayne.edu/oa_dissertations/4104