INVESTIGATING ULTRAFAST EQUILIBRIUM AND NON-EQUILIBRIUM DYNAMICS IN THE CONDENSED PHASE WITH MOLECULAR VIBRATIONS

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Degree type
Doctor of Philosophy (PhD)
Graduate group
Chemistry
Discipline
Chemistry
Subject
2DIR
anion exchange membrane
ion dynamics
physical chemistry
spectroelectrochemistry
vibronic coupling
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2024
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BALL, RANADEB
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Abstract

The vibrational dynamics of small molecules in the condensed phase provide rich information about their structure and interactions with the local microscopic environment. Understanding these interactions on an ultrafast timescale is crucial for predicting their role in chemical processes. Third-order nonlinear spectroscopic techniques such as two-dimensional infrared spectroscopy (2DIR) and polarization dependent mid-IR pump-probe spectroscopy, can map ultrafast vibrational energy relaxation pathways and interaction dynamics of the probe molecules with their local molecular level environment. With pump-probe and 2DIR spectroscopy, I explore the impact of metal ion binding and the impact of electron transfer on the vibrational dynamics of different molecular systems. I find that the vibrational dynamics are sensitive to ion binding and changes associated with electron transfer, and that the net change in the vibrational dynamics across systematically varied series can serve as molecular-level reporters of these chemical processes. In addition to investigating vibrational dynamics of small molecules, I also apply 2DIR to study the dynamics of ion transport in solid polymeric electrolytes to understand how local electric fields, dielectric properties, and water hydrogen bond dynamics influence ionic motion. Combining the experimental results from 2DIR spectroscopy and electrochemical impedance spectroscopy along with computational results we aim to develop design principles to enhance single ion conductivity in sub-nanometer confined ion channels, which has potential applications in electrochemical energy storage. Next, I will discuss the importance of vibronic coupling interactions in the ultrafast vibrational dynamics of a multiconfiguration molecular system, and the ability of 2DIR spectroscopy to probe vibronic interactions. Vibrational dynamics are generally influenced by vibrational mode-mode coupling, intramolecular vibrational energy redistribution, and relaxation to bath modes. By studying a model multiconfiguration system we observe novel dynamics in the 2DIR spectra that arise from vibronic coupling interactions when high-frequency vibrations are excited with mid-infrared pulses. Such IR-induced vibrational control of the low-lying electronic states offers the potential for controlling the ultrafast electronic polarization, advancing our understanding of molecular electronics.

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Anna, Jessica
Date of degree
2024
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