Hannover 2010 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 7: Poster: Femtosecond Spectroscopy

MO 7.17: Poster

Dienstag, 9. März 2010, 16:00–18:30, Lichthof

Electronic Structure and Dynamics of Cytosine — Kyriaki Kosma, •Christian Schröter, Ingolf-Volker Hertel, and Thomas Schultz — Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin

The characterization of the relaxation processes in isolated DNA bases (adenine, thymine, cytosine, and guanine) may help to understand the photostability of DNA upon UV irradiation.

For cytosine three tautomers have been observed in the gas phase: the enol, keto, and keto-imino forms [1]. We studied the electronic structure and dynamics of these tautomers by means of time-resolved mass and photoelectron spectroscopy.

Three ionic transients with lifetimes of femtoseconds to hundreds of picoseconds lifetimes are observed for the biologically relevant keto tautomer and are correlated with broad, unstructured electron bands. The data are assigned to internal conversion and excited-state tautomerization or intersystem crossing. Only two transients with femtosecond and picosecond lifetimes are identified for the enol or keto-imino tautomer and are assigned to internal conversion processes [2].

[1] Brown R. D. et al., J. Am. Chem. Soc. 1989, 111, 2308

[2] Kosma K. et al, J. Am. Chem. Soc. 2009, 131, 16939