Mainz 2017 – scientific programme

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MO: Fachverband Molekülphysik

MO 13: Probing Vibrations

MO 13.1: Invited Talk

Thursday, March 9, 2017, 11:00–11:30, N 6

Ultrafast solvent fluctuations steer the hydrated excess proton in the Zundel cation H₅O₂⁺ — •Fabian Dahms¹, Rene Costard¹, Ehud Pines², Eva Maria Brüning¹, Torsten Siebert¹, Benjamin P. Fingerhut¹, Erik T. J. Nibbering¹, and Thomas Elsaesser¹ — ¹Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Str. 2a, 12489 Berlin, Germany — ²Department of Chemistry, Ben Gurion University of the Negev, P.O.B. 653, Beersheva 84105, Israel

Hydrated protons are a key feature of biochemical systems. Not only do they mediate charge transport in aqueous environments but also play a key role in cell respiration. The Zundel cation represents a prototype species in which a proton is hydrated by two water molecules. By two-color femtosecond pump-probe measurements we were able to dissect the so-called Zundel infrared absorption continuum from the OH stretching and bending vibrations^[1]. In combination with theory, this led to a new picture where ultrafast solvent fluctuations modulate the position of the central H+ atom in the Zundel cation (H₅O₂⁺) causing the extreme broadening of infrared absorption.For the first time we investigate the dynamical behaviour of the O– H⁺–O proton transfer coordinate with femtosecond two-dimensional infrared spectroscopy. First results suggest ultrafast spectral diffusion, frequency shifts and vibrational lifetimes on a sub-100 fs time scale. In combination with results from pump-probe spectroscopy and theory, this gives new insight into vibrational motions of the hydrated proton itself. [1]: Dahms, Fabian, et al., Angew. Chem. Int. Ed. 55 (2016): 10600.