Düsseldorf 2007 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 13: Photochemistry
MO 13.8: Vortrag
Montag, 19. März 2007, 18:15–18:30, 6B
H-transfer reaction in 2-aminopyridine dimer studied by fs pump-probe spectroscopy — •Elena Samoylova1, Yuliya Rulyk1, Dirk Nolting1, Hans-Hermann Ritze1, Wolfgang Radloff1, Ingolf Volker Hertel2, and Thomas Schultz1 — 1Max Born Institute, Max-Born Str.2A, Berlin, Germany — 2Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, Berlin, Germany
H-bonded intermolecular interactions play a very important role in the biophysics of DNA, determining its structure and dynamics. For the electronically excited states, theory predicted a very fast deactivation mechanism involving H-transfer along the N-H coordinate in DNA base pairs. This mechanism can quench highly reactive excited states and provide the necessary photostability against photoinduced damage for the genetic information. We studied the H-transfer mechanism in 2-aminopyridine dimer, a model system for H-bound Watson-Crick DNA base pairs. Using time-resolved ion and electron spectroscopy we identified a fast deactivation pathway of the excited state (life time is 69 ps at 274 nm). Higher vibrational excitation at 250 nm lead to a slight increase of the life time to 75 ps, and we observed an additional ultrafast (less then 50 fs) deactivation channel. The ultrafast contribution can be explained by the initial wave packet motion along N-H stretching mode carrying part of the population over the H-transfer barrier. The remaining population is caught in the local minimum and decays on the ps time scale.