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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 69: Focus: Fundamentals of molecular liquids, ionic liquids and mixtures II
CPP 69.8: Vortrag
Mittwoch, 18. März 2020, 17:30–17:45, ZEU 222
Barrier-crossing infrared spectral signatures of proton-transfer dynamics in the H5O2+ cation — •Florian N. Brünig and Roland R. Netz — Institut für theoretische Physik, Freie Universität Berlin
The direct intermediate of the excess-proton transfer in water is the H5O2+ or Zundel cation, the simplest system for which the excess proton performs a barrier crossing, separating two meta-stable configurations, namely the association to either one of the two water molecules. Several recent 2D infrared spectroscopy studies identify a low-barrier double-well potential for this proton transfer between two water molecules in the bulk phase [1,2], which was confirmed in simulations and associated with continuum bands [3]. We now developed a general theory to predict the spectral signature of barrier-crossing processes and applied it to trajectories obtained from ab-initio molecular-dynamics simulations of the H5O2+ cation thus capturing non-linearities and line shapes. We find three distinct contributions: the quasi-harmonic motion around the most probable configurations, which can be understood by normal-mode analysis, the fast transition-path contribution over the barrier and a low-frequency tail.
[1] Elsaesser, T. et. al. (2017) Science, 357, 491-495.
[2] Tokmakoff, A. et. al. (2018) Nature Chemistry, 10, 932-937
[3] Netz, R. R. et. al. (2018) Nature Communications, 9, 311