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arXiv · 2212.12875

Femtosecond Symmetry Breaking and Coherent Relaxation of Methane Cations at the Carbon K-Edge

Enrico Ridente·Diptarka Hait·Eric A. Haugen·Andrew D. Ross·Daniel M. Neumark·Martin Head-Gordon·Stephen R. Leone
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Abstract

Understanding the relaxation pathways of photoexcited molecules is essential to gain atomistic level insight into photochemistry. Herein, we perform a time-resolved study of ultrafast molecular symmetry breaking via geometric relaxation (Jahn-Teller distortion) on the methane cation. Attosecond transient absorption spectroscopy with soft X-rays at the carbon K-edge reveals that the distortion occurs within $10\pm 2$ femtoseconds after few-femtosecond strong-field ionization of methane. The distortion activates coherent oscillations in the scissoring vibrational mode of the symmetry broken cation, which are detected in the X-ray signal. These oscillations are damped within $58\pm13$ femtoseconds, as vibrational coherence is lost with the energy redistributing into lower-frequency vibrational modes. This study completely reconstructs the molecular relaxation dynamics of this prototypical example and opens new avenues for exploring complex systems.

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Enrico Ridente, Diptarka Hait, Eric A. Haugen, Andrew D. Ross, Daniel M. Neumark, Martin Head-Gordon, Stephen R. Leone. 2022-12-25. Femtosecond Symmetry Breaking and Coherent Relaxation of Methane Cations at the Carbon K-Edge. https://doi.org/10.1126/science.adg4421

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