Bonn 2025 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 13: Ultrafast Dynamics II

MO 13.1: Vortrag

Mittwoch, 12. März 2025, 11:00–11:15, HS XVI

Photo-induced structural dynamics of thymine with ultrafast electron diffraction — •Xiaojun Wang¹, Jackson Lederer², Dennis Mayer¹, Fabiano Lever¹, Pedro Nunes², Yusong Liu³, Surjendu Bhattacharyya³, Nikhil Pachisia², Xinxin Cheng³, Tianzhe Xu³, Stephen Weathersby³, Randy Lemons³, Patrick Kramer³, Philipp Lenzen³, Ming-Fu Lin³, Kirk Larsen³, Fuhao Ji³, Robert England³, Christina Hampton³, Brian Kaufman³, Alice Green³, Alexander Reid³, Todd Martinez^3,4, Thomas Wolf³, Martin Centurion², and Markus Guehr^1,5 — ¹Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany — ²Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, USA — ³SLAC National Accelerator Laboratory, Menlo Park, USA — ⁴Department of Chemistry, Stanford University, Stanford, USA — ⁵Institute of Physical Chemistry, University of Hamburg, Hamburg, Germany

The photoprotection mechanism of thymine involves complex relaxation dynamics, where energy from photoexcitation is converted into vibrational energy through radiationless transitions. Previous studies have indicated that isolated thymine molecules undergo ¹ππ^* → ¹nπ^* internal conversion within 100 femtoseconds (fs), followed by the intersystem crossing from ¹nπ^* to the triplet state within 10 picoseconds (ps). However, the nuclear dynamics accompanying the transitions have not been experimentally resolved. Here we present a direct observation of the ultrafast nuclear motions using ultrafast electron diffraction, on the fs timescale and sub-Ångstrom resolution.

Keywords: Ultrafast electron diffraction; Ultrafast structural dynamics; Photochemistry; Excited state dynamics; Conical intersection