Femtosecond symmetry breaking and coherent relaxation of methane cations via x-ray spectroscopy

• 成果类型: Article
• 署名作者: Ridente, Enrico; Hait, Diptarka; Haugen, Eric A.; Ross, Andrew D.; Neumark, Daniel M.; Head-Gordon, Martin; Leone, Stephen R.
• 署名单位: University of California System; University of California Berkeley; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory; University of California System; University of California Berkeley; Stanford University; Stanford University
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-13729
• DOI: 10.1126/science.adg4421
• 发表日期: 2023-05-19
• 页码: 713-717
• 关键词: jahn-teller; photoelectron-spectra; DYNAMICS; molecules; STABILITY; cd2h2+; STATES; water; ch4+

摘要

Understanding the relaxation pathways of photoexcited molecules is essential to gain atomistic-level insight into photochemistry. We performed a time-resolved study of ultrafast molecular symmetry breaking through geometric relaxation (Jahn-Teller distortion) on the methane cation. Attosecond transient absorption spectroscopy with soft x-rays at the carbon K-edge revealed that the distortion occurred within 10 +/- 2 femtoseconds after few-femtosecond strong-field ionization of methane. The distortion activated coherent oscillations in the asymmetric scissoring vibrational mode of the symmetry-broken cation, which were detected in the x-ray signal. These oscillations were damped within 58 +/- 13 femtoseconds because vibrational coherence was lost with the energy redistributing into lower-frequency vibrational modes. This study completely reconstructs the molecular relaxation dynamics of this prototypical example and opens avenues for exploring complex systems.