Wed, 12.01.2022  |  14:00
virtual, via Zoom link
MBI Colloquium

Time-resolved x-ray probing of the photorelaxation in thiouracil

Prof. Dr. Markus Gühr | Universität Potsdam

talks about

The genetic information of life is encoded by nucleobases, which show interesting photo-protective properties. The bases strongly absorb ultraviolet light; nevertheless, the internal electronic energy is converted into harmless vibrations of many bonds on an ultrafast timescale.

Substituting one or two oxygen atoms of the nucleobases by sulfur results in the so called thio-nucleobases, which have been used or discussed as drugs for immune-suppression, photoinduced cancer therapy as well as markers for cross linking. The broad use of thio-nucleobases is due to drastic changes in the ultrafast relaxation compared to the canonical counterparts. Photoexcited thionucleobases relax to long-lived and cytotoxic triplet states.

We show the results of UV pump - x-ray probe experiments on 2-thiouracil at the sulfur edges, performed at FLASH. We observe transient shifts of the Auger spectra and the 2p photoline. We show, that time-resolved x-ray photoemission (XPS) on the photoexcited molecular state gives direct insight on valence charge redistribution over the molecular body. Finally, we compare the information content of time-resolved XPS to other ultrafast methods.

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