Berlin 2005 – wissenschaftliches Programm
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MO: Molekülphysik
MO 15: Biomolecules II
MO 15.7: Vortrag
Freitag, 4. März 2005, 18:30–18:45, HU 2097
Excited state dynamics in the solvated DNA base adenine — •Valoris Reid Smith, E. Samoylova, H. Lippert, H.-H. Ritze, W. Radloff, I.V. Hertel, and Th. Schultz — Max-Born-Institut Berlin, Max-Born Strasse 2a, 12489 Berlin, Germany
The extraordinary robustness of DNA with respect to damage by the harmful UV components of sunlight may have been crucial to the development of life on earth. The structural complexity of DNA hinders an understanding of the underlying photophysical processes. To simplify the analysis, we studied the isolated DNA base adenine, and microsolvated water clusters thereof by femtosecond time resolved spectroscopy and photoelectron photoion coincidence measurements. Two competing relaxation pathways were identified: (a) ππ∗ to nπ∗ internal conversion followed by a picosecond relaxation back to the ground state and (b) ππ∗ to πσ∗ internal conversion followed by ultrafast relaxation to the ground state.
In Adenine-water clusters, the ππ∗ to πσ∗ process dominated the observed reaction dynamics. This was explained by the lowering of the πσ∗ state energy in the water clusters. In the Adenine(H2O)2 cluster, an additional process leads to a yet unidentified state with a very long lifetime.