Large-amplitude transfer motion of hydrated excess protons mapped by ultrafast 2D IR spectroscopy

• Autores: Fabian Dahms, Benjamin P. Fingerhut, Erik T.J. Nibbering
• Localización: Science, ISSN 0036-8075, Vol. 357, Nº 6250, 2017, págs. 491-495
• Idioma: inglés
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• Resumen

  • Solvation and transport of excess protons in aqueous systems play a fundamental role in acid-base chemistry and biochemical processes. We mapped ultrafast proton excursions along the proton transfer coordinate by means of two-dimensional infrared spectroscopy, both in bulk water and in a Zundel cation (H5O2)+ motif selectively prepared in acetonitrile. Electric fields from the environment and stochastic hydrogen bond motions induce fluctuations of the proton double-minimum potential. Within the lifetime of a particular hydration geometry, the proton explores a multitude of positions on a sub-100-femtosecond time scale. The proton transfer vibration is strongly damped by its 20- to 40-femtosecond population decay. Our results suggest a central role of Zundel-like geometries in aqueous proton solvation and transport.