Hannover 2016 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 20: Femtosecond Spectroscopy 4

MO 20.7: Vortrag

Freitag, 4. März 2016, 12:30–12:45, f102

Photocleavage of coumarin dimers studied by UV ultrafast transient absorption spectroscopy — •Man Jiang, Tiago Buckup, and Markus Motzkus — Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität, D- 69120 Heidelberg, Germany

The photoinduced cleavage of a coumarin dimer into its two monomers is a promising mechanism for laser controlled medical applications, like the release of pharmaceutical drugs for on-demand in-vivo treatment. In order to understand the underlying dynamics of the cleavage reaction in detail and develop strategies for an increase of the reaction efficiency, UV transient absorption spectroscopy was applied to a typical coumarin dimer, 2-methylallylcarboxy-dicoumarin (linker 2). Linker 2 has an intact lactone ring structure and leads to a symmetric cleavage yielding the sole monomer product. Exciting the dimer with ultrashort pulses at 280 nm with 30 fs pulse duration, we were able to explore the precise time-scale of coumarin monomers formation and to determine the quantum yield of the dimer splitting. A branched kinetic model was developed which describes the formation of monomer and relaxation dynamics to the ground state with the corresponding rate constants. The branching ratio between the two pathways is about 1:2. Furthermore, the dependence of the dynamics of the cleavage reaction on the dimer side group substitution will be discussed.