"Symmetry Breaking Wavepacket Motion and Absence of Deuterium Isotope Effect in Ultrafast Excited State Proton Transfer"S. Lochbrunner, K. Stock, C. Schriever, and E. Riedle
Femtochemistry and Femtobiology: Ultrafast Events in Molecular Science, M. M. Martin and J. T. Hynes, eds. (Elsevier, Amsterdam, 2004), 193 - 196
The double proton transfer of [2,2'-Bipyridyl]-3,3'-diol is investigated by UV-visible pump-probe spectroscopy with 30 fs time resolution. We find characteristic wavepacket motions for both the concerted double proton transfer and the sequential proton transfer that occur in parallel. The coherent excitation of an optically inactive, antisymmetric bending vibration is observed demonstrating that the reactive process itself and not only the optical excitation drives the vibrational motions. We show by the absence of a deuterium isotope effect that the ESIPT dynamics is entirely determined by the skeletal modes and that it should not be described by tunneling of the proton.
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