Berlin 2005 – wissenschaftliches Programm

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MO: Molekülphysik

MO 15: Biomolecules II

MO 15.6: Vortrag

Freitag, 4. März 2005, 18:15–18:30, HU 2097

Excited state dynamics of isolated DNA bases and base pairs — •Elena Samoylova, Th. Schultz, W. Radloff, H.-H. Ritze, and I.V. Hertel — Max-Born Institut Berlin, Max-Born-Str. 2A, D-12489 Berlin, Germany

We describe excited state dynamics of adenine_n and thymine_n clusters (n=1,2,3) with femtosecond pump-probe mass and electron spectroscopy. The clusters were excited with 250-272 nm pulses and ionized with 800 nm. The monomers decay to the electronic ground state through the nπ^∗ state with time constants of 1 ps for adenine and 6.5 ps for thymine. A similar relaxation pathway is found in thymine clusters. In contrast to this, time-dependent signals of adenine dimer suggest an additional relaxation channel via the πσ^∗ state that is much faster (< 50 fs). The dynamics of the adenine-thymine heterodimer indicate both relaxation channels described above. Different isomers may contribute to the cluster signals observed in our gas phase experiments. A new experimental approach combining hole burning method with femtosecond time-resolved spectroscopy is suggested to resolve this issue.