Abstract
Time-resolved X-ray methods are widely used for monitoring transient intermediates over the course of photochemical reactions. Ultrafast X-ray absorption and emission spectroscopies as well as elastic X-ray scattering deliver detailed electronic and structural information on chemical dynamics in the solution phase. In this work, we describe the opportunities at the Femtosecond X-ray Experiments (FXE) instrument of European XFEL. Guided by the idea of combining spectroscopic and scattering techniques in one experiment, the FXE instrument has completed the initial commissioning phase for most of its components and performed first successful experiments within the baseline capabilities. This is demonstrated by its currently 115 fs (FWHM) temporal resolution to acquire ultrafast X-ray emission spectra by simultaneously recording iron Kα and Kβ lines, next to wide angle X-ray scattering patterns on a photoexcited aqueous solution of [Fe(bpy)3]2+, a transition metal model compound.
Highlights
Time-resolved chemical dynamics experiments exploiting hard X-radiation have become a mainstream option over the past 20 years, and part of the vast field of Femtochemistry [1]
It quickly became clear that studying photoexcited solutes using X-ray emission spectroscopy (XES) and wide-angle X-ray scattering (WAXS) in the same experiment can provide a deeper understanding of the interplay between structural and electronic structural dynamics
Already in the Fall of 2019 the European XFEL machine has demonstrated stable lasing with 16.5 GeV electrons resulting in 20 keV X-ray photons with up to 900 μJ energy per pulse in the Femtosecond X-ray Experiments (FXE) branch
Summary
Time-resolved chemical dynamics experiments exploiting hard X-radiation have become a mainstream option over the past 20 years, and part of the vast field of Femtochemistry [1]. It quickly became clear that studying photoexcited solutes using XES and WAXS (or solution scattering) in the same experiment can provide a deeper understanding of the interplay between structural and electronic structural dynamics This was demonstrated with SR [10,16] and XFEL [24,25,26,27] radiation in benchmarking studies, and today most hard X-ray FEL sources do include. Located at the so called SASE1 undulator of European XFEL, FXE exploits the unprecedented X-ray flux available, which can deliver up to two orders of magnitude more photon flux than other XFEL facilities This leap in X-ray power should open up new methods in structural dynamics investigations, enabling flux-hungry tools like. The high X-ray photon energy of up to 25 keV in the fundamental lasing radiation will allow exploiting WAXS tools on solvated chromophores, which will deliver more precise structural information about the photoexcited dynamic structures compared to the existing benchmark studies [28,29,30,31]
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