Degree

Doctor of Philosophy (PhD)

Department

Department of Physics and Astronomy

Document Type

Dissertation

Abstract

Particle-like charge migration (CM) is the coherent, back-and-forth motion of a positively-charged electron hole along the backbone of a molecule following a sudden ionization. CM in small molecules generally occurs on an Angstrom (10-10 m) spatial scale and an attosecond (10-18 s) timescale. I use time-dependent density-functional theory (TDDFT) to simulate CM modes in organic molecules, and to explore all-optical probes of this attosecond electron dynamics using high-harmonic spectroscopy (HHS). By leveraging my results from previous studies of two-center interferences in carbon dichalcogens, in which I separated the harmonic signal into contributions from individual Kohn-Sham orbitals, I first develop high-harmonic sideband spectroscopy (HHSS) as a robust, background-free, and all-optical probe of particle-like CM dynamics. The CM manifests in the high-order harmonic signal as a beat in the time domain and as sidebands in the frequency domain and over several laser cycles. By varying the driving laser wavelength, I am able to extract the characteristic frequency of the relevant CM mode. Then, by exploiting the inherent time-resolution of the high-harmonic generation process (the attochirp), I develop frequency-matched strobo-spectroscopy (FMSS). Here, I vary the delay between the initiation of the CM dynamics and a few-cycle laser pulse in order to track the location of the electron hole along the molecular backbone as a function of time.

Date

4-9-2024

Committee Chair

Mauger, Francois

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