Stuttgart 2012 – scientific programme

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MO: Fachverband Molekülphysik

MO 17: Femtosecond Spectroscopy IV

MO 17.5: Talk

Thursday, March 15, 2012, 11:45–12:00, V38.03

Ultrafast Electronic Deactivation Dynamics of the Rare Natural Nucleobases Xanthine and Hypoxanthine — •Katharina Röttger and Friedrich Temps — Institute of Physical Chemistry, Christian-Albrechts-University Kiel, Olshausenstr. 40, D 24098 Kiel, Germany

Investigations of the photophysical behaviour of rare DNA and RNA bases provide insight into the correlation between structural properties of the nucleobases and their radiationless decay pathways after UV excitation. Here, we report on the first femtosecond time-resolved transient absorption measurements of the rare RNA nucleotide xanthosine monophosphate in buffered aqueous solution at different pH values and on the rare natural RNA base hypoxanthine. Measurements were performed with a transient absorption setup which allows for a highly sensitive, simultaneous detection of broadband absorption spectra (300-700 nm) and single-colour absorption in the deep UV range. The excited-state dynamics of xanthosine monophosphate (XMP) have been found to depend strongly on the excitation wavelength. It was possible to distinguish the dynamics of two close lying ππ* states which are most likely connected via a conical intersection. The direct observation of the consecutive population of these states is quite rare in the case of the nucleobases. The dynamics of hypoxanthine were found to be similar to those of guanine. The results are discussed in comparison with recently published computational studies on possible relaxation channels.