Düsseldorf 2007 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 19: Photoionization
A 19.1: Hauptvortrag
Donnerstag, 22. März 2007, 11:30–12:00, 5M
Photophysics of DNA: Relation between structure and dynamics in isolated clusters — •Thomas Schultz1, Elena Samoylova1, Hans-Hermann Ritze1, Wolfgang Radloff1, Yuliya Rulyk1, and Ingolf Volker Hertel1,2 — 1Max-Born-Institut Berlin, Max-Born-Str. 2A, 12489 Berlin — 2Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin
The photophysics of DNA is governed in part by intrinsic properties of the DNA bases, but also by intermolecular interactions with the local environment. Investigation of the latter is particularly difficult due to the multitude of relevant noncovalent interactions and the intimate relationship between the local structure and the position and shape of excited state potential energy surfaces, which determine the outcome of excited state dynamic processes.
We reduce this complexity by investigating the photophysics in small, isolated molecular clusters, e.g. hydrogen-bound or stacked base pairs and microhydrated bases. Pump-probe photoionization spectroscopy identified ultrafast processes involving bright and dark electronic states, a hydrogen transfer reaction and delocalized excimer states. Most observed processes lead to ultrafast excited state relaxation and help to explain the extraordinary photostability of DNA. Comparison to ab initio calculations offered insight into the importance of particular interactions such as specific hydrogen bonds or the environment polarizability. Small clusters with suitable geometry seem to reproduce processes in real DNA and may extend our detailed understanding of isolated molecules towards complex biological systems.