Ultrafast X-ray Photochemistry at European XFEL: Capabilities of the Femtosecond X-ray Experiments (FXE) Instrument

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.

Effect of X-ray free-electron laser-induced shockwaves on haemoglobin microcrystals delivered in a liquid jet

“…XFEL-induced shockwaves may be relevant not just to crystalline samples, but also to XFEL scattering from solutions of proteins or other molecules 49 . While SFX experiments are typically conducted in thin microjets (diameter 3-5 μm), most spectroscopy experiments [50][51][52] employ large diameter Rayleigh jets (~30-100 μm) as do also many SAXS and wide-angle solution scattering experiments 50 . Again unknown balances remain to be investigated: larger jets are generally slower, likely requiring EuXFEL operation at <4.5 MHz maximum in order to clear the gap 50 .…”

“…While SFX experiments are typically conducted in thin microjets (diameter 3–5 µm), most spectroscopy experiments 50 – 52 employ large diameter Rayleigh jets (~30–100 μm) as do also many SAXS and wide-angle solution scattering experiments 50 . Again unknown balances remain to be investigated: larger jets are generally slower, likely requiring EuXFEL operation at <4.5 MHz maximum in order to clear the gap 50 . This yields an increased distance of travel and thereby a greater relative attenuation of the shock.…”

Exploring the light-induced dynamics in solvated metallogrid complexes with femtosecond pulses across the electromagnetic spectrum

“…The present work reports the first steps toward obtaining exhaustive characterizations of the photoinduced dynamics in oligonuclear TM complexes using mid-IR, UV-vis, and x-ray femtosecond pulses. The reversible photocycle of a solvated pyrazolatebridged [2 × 2] Fe II metallogrid complex is probed with femtosecond TOA and TIA spectroscopies along with TXE spectroscopy at the FXE instrument (Galler et al, 2019;Khakhulin et al, 2020) of the European XFEL (EuXFEL) facility (Altarelli, 2015;Tschentscher et al, 2017). Correlating the relevant time scales associated with the coupled electronic, vibrational, and spin dynamics allows building a detailed picture of the PSS process in this important family of oligonuclear TM complexes that will guide the development of their light-driven applications based on spin-switching in the solution phase.…”

Accurate, Affordable, and Generalisable Machine Learning Simulations of Transition Metal X-ray Absorption Spectra using the XANESNET Deep Neural Network

“…[26][27][28][29][30][31][32][33] Here, there have been significant successes with machine learning models that redress the accuracy/affordability balance of atomistic modelling -from parametric force-fields [34][35][36][37][38] to accurate quantum mechanical properties obtained from low-cost electronic structure calculations [39][40][41][42][43] and accelerated excited-state molecular dynamics. [44][45][46][47][48][49][50][51][52][53][54][55] It ought to be of no great surprise that spectroscopyalready in renaissance following fast-paced developments in methodology and instrumentation, especially at highbrilliance light sources [56][57][58][59][60] should also be simultaneously a) Electronic mail: conor.rankine@ncl.ac.uk b) Electronic mail: tom.penfold@ncl.ac.uk transformed by machine learning. 61 Indeed, the two are a natural pairing; machine learning is similarly grounded in linear mathematics (e.g.…”