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arXiv · 2601.22750

Femtosecond Nonadiabatic Confinement of Molecular Dication Yield

Carlos Marante·Lina Fransén·Alexie Boyer·Vincent Loriot·Franck Lépine·Luca Argenti·Morgane Vacher·Saikat Nandi
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Abstract

Doubly charged molecular cations often carry signatures of electronic correlation and electron-nuclear entanglement present in the parent cation. Here, we produce ethylene dications using a combination of an extreme ultraviolet pump and near-infrared probe pulses, observing a peak in the dication yield at a pump-probe delay of approximately 15 fs. Ab-initio calculations, which explicitly take into account coupled electron-nuclear dynamics induced by the pump and the multiphoton nature of the probe-induced ionization step, reproduced the observed delay in the yield. It originates from resonant enhancement of the multiphoton ionization of the electronically excited ethylene cation as the carbon-carbon double bond expands. However, this effect is tempered by rapid nonadiabatic relaxation of the excited ionic states. Our results suggest a general mechanism whereby ultrafast nonadiabatic relaxation of a molecular ion can compete with its strong-field ionization rate, confining the dication yield to a narrow temporal window of a few femtoseconds.

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Carlos Marante, Lina Fransén, Alexie Boyer, Vincent Loriot, Franck Lépine, Luca Argenti, Morgane Vacher, Saikat Nandi. 2026-01-30. Femtosecond Nonadiabatic Confinement of Molecular Dication Yield. https://doi.org/10.1021/acs.jpclett.5c03271

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