Berlin 2005 – wissenschaftliches Programm
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MO: Molekülphysik
MO 42: Poster II
MO 42.1: Poster
Dienstag, 8. März 2005, 14:00–16:00, Poster HU
Study of the lowest πσ* states in adenine and complexes with adenine — •Hans-Hermann Ritze1, Thomas Schultz1, Wolfgang Radloff1, and Ingolf Volker Hertel1,2 — 1Max-Born-Institut, Max-Born-Str. 2A, D-12489 Berlin, Germany — 2Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
In many aromatic biomolecules after optical excitation of the ππ* state an internal conversion to the dissociative Rydberg-type πσ* state takes place. The photophysics of the DNA base adenine is of special interest because here additionally for an essential nonplanar configuration there exists a smooth energy path from ππ* via nπ* to the ground electronic state dominating in the bare molecule..
We have carried out ab initio calculations at the CASPT2 level to study the two lowest πσ* potential curves in bare adenine including the effect of the zero-point energy. We found that in a polar environment (e.g., adenine-water complexes) the πσ* state is energetically lowered. This effect can explain the experimentally observed considerable reduction of the excitation lifetime down to 100 fs.