Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse

Abstract

Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10−18 s) to femtoseconds (10−15 s) and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS), we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.

Photoinduced Structural Dynamics of Molecular Systems Mapped by Time-Resolved X-ray Methods

“…360 In a time-resolved mode, it would avoid having to scan the energy to record a transient XAS. The high fluxes and coherence properties of XFELs are also opening the field to new nonlinear X-ray spectroscopies, similar to what happened following the birth of the laser decades ago.…”

High energy resolution off-resonant spectroscopy: A review

“…A first HEROS experiment at a XFEL operated in the self-seeded mode [82] was performed on Cu and different Cu oxides around the Cu K-edge [48]. A von Hamos spectrometer operated in a multi-crystal arrangement was used to monitor simultaneously the signals from the Ka and the Kb emission lines [83] (see Fig.…”

“…Only recently, a wavelength-dispersive von Hamos-geometry-based spectrometer was used to measure in high resolution single-shot spectra of off-resonantly scattered X-rays, establishing thus the high energy resolution off-resonant spectroscopy (HEROS) [40][41][42]. Until now different research studies on HEROS have been realized at synchrotrons as well as at XFELs and the method found numerous applications in in situ time-resolved chemical speciation experiments [40,41,[43][44][45][46][47][48][49][50][51]. HEROS is a new approach and is becoming more and more recognized in the field of X-ray spectroscopy (see, e.g., Refs.…”

A compact and versatile tender X-ray single-shot spectrometer for online XFEL diagnostics

“…1). The von Hamos spectrometer has been developed for RIXS measurements at PSI (Szlachetko et al, 2012(Szlachetko et al, , 2013 as a tool for high-resolution spectroscopy of various samples at synchrotron and XFEL (Szlachetko et al, 2014(Szlachetko et al, , 2016) radiation sources. The setup collects scattered photons over a large scattering angle onto an optical element composed of thin segmented Si crystals glued to a cylindrically bent substrate.…”