Stuttgart 2012 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 17: Femtosecond Spectroscopy IV

MO 17.6: Vortrag

Donnerstag, 15. März 2012, 12:00–12:15, V38.03

Ultrafast dynamics of NH stretch vibrations in adenosine-thymidine base pairs in chloroform solution — •Christian Greve1, Benjamin Koeppe1, Henk Fidder1, Nicholas Preketes3, Erik T. J. Nibbering1, Shaul Mukamel3, Friedrich Temps2, and Thomas Elsaesser11Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, 12489 Berlin, Germany — 2Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, 24098 Kiel, Germany — 3Department of Chemistry, University of California, Irvine, USA

The nucleobases adenine (A) and thymine (T), building blocks in native DNA and RNA, readily form hydrogen bonded complexes both in the gas phase and in solution. To gather key insight into these hydrogen bonding interactions, we perform femtosecond IR-pump-IR-probe and polarization-resolved 2D-IR photon echo spectroscopy of the N-H stretching bands of AT base pairs in chloroform solution which are located between 3100 and 3500 cm−1. Vibrational population dynamics of hydrogen bonded stretch transitions occur on a subpicosecond time scale. Cross peaks in the 2D-IR spectra, monitored as a function of waiting time, show the connectivities in the N-H stretching manifold. The polarization dependence of the cross peaks indicate that the hydrogen-bonded and the free N-H stretching dipole moments in these AT base pairs have a well-defined relative orientation. Our experimental results are combined with quantum chemical calculations to allow for N-H stretching mode assignments of the Watson-Crick and Hoogsteen base pair structural motifs present in solution.

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