Attosecond X-ray spectroscopy reveals the competing stochastic and ballistic dynamics of a bifurcating Jahn–Teller dissociation
Year: 2025
Type: article
Abstract: A fundamental approach to understanding chemical processes involves two key concepts: reaction paths and vibrational wavepackets. Collecting sufficient observables to experimentally determine these paths still challenges the latest advances in ultrafast science. Simultaneously observing the coherent nature of the wavepacket following them is even more challenging. Here, exploiting the sub-femtosecond time resolution (σ = 1 fs) of attosecond soft-X-ray-absorption spectroscopy, we overcome both of these challenges and observe a Jahn-Teller-mediated chemical reaction in its entirety—from initial symmetry breaking to beyond dissociation. We find that the Jahn-Teller effect in $${{{{{{\rm{SiH}}}}}^{+}_{4}}}$$ immediately bifurcates the reaction into two channels: ballistic dissociation into $${{{{{{\rm{SiH}}}}}^{+}_{3}}}$$ and H in 22.9 ± 0.5 fs in which the vibrational wavepacket is preserved, and—after an induction time of 11 ± 3.4 fs—a stochastic dissociation into $${{{{{{\rm{SiH}}}}}^{+}_{2}}}$$ and H2 with a timescale of 140 ± 19 fs in which the wavepacket dephases. We find that adiabatic ab-initio molecular dynamics simulations correctly reproduce the ballistic channel, but fail with the stochastic channel. These unprecedented insights into an ultrafast Jahn-Teller-mediated chemical reaction establish the unique potential of our experimental scheme for investigating chemical processes, particularly ones containing non-adiabatic dynamics or involving hydrogen atoms, which are notoriously difficult to detect with other methods, such as electron or X-ray diffraction. The Jahn-Teller effect leads to the distortion of molecular structures in electronically degenerate states. Here the authors use attosecond X-ray spectroscopy to follow this process in the silane cation, observing how the distortion splits into one coherent and one stochastic pathway.
Source: Nature Communications
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $6,990
OpenAlex ID: W4412469257