Freiburg 2024 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 11: X-ray Spectroscopy

MO 11.3: Vortrag

Mittwoch, 13. März 2024, 11:30–11:45, HS 3044

X-ray absorption of CF₄ driven by x-ray free-electron laser — •Rui Jin¹, Adam Fouda², Alexander Magunia¹, Marc Rebholz¹, Alberto De Fanis³, Kai Li², Gilles Doumy², Jan-Erik Rubensson⁴, Maria Novella Piancastelli⁵, Marc Simon⁵, Thomas Baumann³, Michael Straub¹, Sergey Usenko³, Yevheniy Ovcharenko³, Tommasso Mazza³, Nina Rohringer^6,7, Michael Meyer³, Linda Young^2,8, Christian Ott¹, and Thomas Pfeifer¹ — ¹MPIK, Heidelberg — ²Argonne National Laboratory, USA — ³European XFEL, Schenefeld — ⁴Uppsala University, Sweden — ⁵Sorbonne Universités, Paris — ⁶DESY, Hamburg — ⁷Universität Hamburg — ⁸University of Chicago, USA

X-ray absorption spectroscopy (XAS) is widely used to study atomic and molecular structure and dynamics, especially at the core level. X-ray free electron lasers (XFEL) have introduced coherent, high-brilliance, and ultrashort laser pulses with tunable energies, thereby enabling the study of multiphoton x-ray matter interactions. In this work, the EuXFEL is combined with a grating spectrometer for a single-pulse transient absorption study of the intermediate electronic states arising from multiphoton-induced molecular dynamics in CF₄. The central photon energy is tuned to initiate dynamics with and without producing fluorine K-holes. The spectra are measured at different FEL intensities to study multiphoton effects. Two main findings are: (1) neutral fluorine atoms are observed within the pulse duration (40 fs), and (2) short-lived molecular fragments with fluorine 1s-core hole state are observed for high intensities. Precise atomic and molecular structure calculations as well as semi-classical molecular dynamics are used to interpret the results. Overall, this study demonstrates the potential of XFEL-driven transient-absorption spectroscopy to study ultrafast multiphoton dynamics of molecular systems.

Keywords: x-ray absorption; x-ray free-electron laser; ultrafast fragmentation; multiphoton