Erlangen 2022 – scientific programme

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MO: Fachverband Molekülphysik

MO 2: X-ray FELs (joint session MO/A)

MO 2.5: Talk

Monday, March 14, 2022, 15:00–15:15, MO-H5

Ultrafast Auger spectroscopy of 2-thiouracil — •F. Lever¹, D. Mayer¹, D. Picconi¹, J. Metje¹, S. Alisauskas², F. Calegari², S. Düsterer², C. Ehlert³, R. Feifel⁴, M. Niebuhr¹, B. Manschwetus², M. Kuhlmann², T. Mazza⁶, M. S. Robinson⁵, R. J. Squibb⁴, A. Trabattoni⁵, M. Wallner⁴, P. Saalfrank¹, T. J. A. Wolf⁷, and M. Gühr¹ — ¹Universität Potsdam — ²Deutsches Elektronen Synchroton (DESY) — ³Heidelberg Institute for Theoretical Studies — ⁴Department of Physics, Gothenburg University — ⁵Center for Free-Electron Laser Science (CFEL) — ⁶European XFEL — ⁷SLAC, Stanford

Investigating the effects of UV exposure in thionucleobases can shed light on the mechanisms that cause the formation of DNA lesions. In this talk, we show how ultrafast x-ray spectroscopy can be used to gain information on such processes. We study the sulfur 2p Auger spectrum of 2-thiouracil in a uv-pump, x-ray probe experiment at the free electron laser FLASH. We observe ultrafast dynamics in the electron kinetic energy spectrum, happening on time scales of 100fs to 1ps. Using a simple coulomb model for the electron binding energies, aided by quantum chemical calculations of the electronic states energy, we deduce an elongation of the C-S bond on a 100fs time scale. The geometric changes trigger internal conversion from the initally excited S2 state to the S1 state. For longer pump-probe delays, the observerd timescales provide evidence for inter system crossing from the S1 state to the triplet manifold [1].

[1] F Lever et al 2020 J. Phys. B: At. Mol. Opt. Phys. 54 014002