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MO: Fachverband Molekülphysik

MO 9: Femtosecond Spectroscopy I

MO 9.3: Vortrag

Mittwoch, 11. März 2020, 11:30–11:45, f102

Ultrafast photo-ion probing of the relaxation processes of 2-Thiouracil. — •Matthew Scott Robinson, Mario Niebuhr, and Markus Gühr — Universität Potsdam, Institut für Physik und Astronomie, Karl-Liebknecht-Straße 24/25, 14476 Potsdam-Golm, Germany

We study the ultrafast relaxation process of 2-thiouracil after UV photo-excitation with the use of multi-photon pump-probe time-of-flight mass spectroscopy, supported by synchrotron-based single-photon vacuum ultraviolet (VUV) photo-ionization studies performed at the Swiss Light Source.

Here we show that most of the observable dynamics are completed 1 ps after excitation, and identify that the parent is primarily produced through 2-photon processes (when using 266 nm photons), whilst all fragments are 3-photon dependent. In addition, through the use of pump and probe beams with different powers we are able to determine if fragments are produced through [1+2] processes or [2+1] processes.

The VUV studies also suggest that the substitution of one of the oxygen atoms of uracil with sulfur to produce 2-thiouracil, introduces a new fragmentation route for the pyrimidine ring, with either CO or HCNH being ejected to produce a 100 amu fragment; the equivalent fragment in uracil (84 amu) is not observed in similar studies. [1]

1. H.W. Jochims, M. Schwell, H. Baumgärtel, and S. Leach, Chem. Phys. 314, 263 (2005).