The Spectral Signature of the Coherent Electronic Excitation of Ethylene

Overview

CREOL, University of Central Florida Electronic motion governs all chemical transformations. For example, when a short light pulse excites a molecule, it creates a charge fluctuation that migrates at a speed close to 500,000 mph, impacting molecular reactivity. Observing and controlling this ultrafast motion is extremely challenging. Only the birth of attosecond science (Physics Nobel Prize 2023) could finally open a window on the time -resolved study of electron dynamics at its natural attosecond time scale (1 as = 10-18s). In this work, we investigate two methods to observe this motion in ethylene. First, charge migration results in an oscillating electric dipole that radiates like an antenna and can be detected with optical interferometric schemes. Second, a probe pulse is used to eject a photoelectron, whose direction reflects where the charge is instantaneously localized in the molecule. Theory is needed to interpret these complex experiments. Here, we employ ASTRA, a molecular ionization code, that can simulate the electr onic motion in the presence of light pulses. In the optical scheme, a first pulse induces a coherent excitation of two lowest states of ethylene, while a second pulse probes this coherence by promoting third -harmonic emission from either of the two states, giving rise to an observable interference. The same coherent motion is also studied by photo -ionizing the excited molecule, monitoring how the photoemission direction changes with time. These findings open new ways to control charge -transfer processes in unsaturated molecules, with potential applications to quantum computing and communication, and in photoreceptors, with application in light-harvesting technology. Georgia

Competition history

• JSHS 2024 Category not listed

Resources

• National JSHS abstract book ↗

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