Photon-in photon-out hard X-ray spectroscopy at the Linac Coherent Light Source

Abstract

X-ray free-electron lasers (FELs) have opened unprecedented possibilities to study the structure and dynamics of matter at an atomic level and ultra-fast timescale. Many of the techniques routinely used at storage ring facilities are being adapted for experiments conducted at FELs. In order to take full advantage of these new sources several challenges have to be overcome. They are related to the very different source characteristics and its resulting impact on sample delivery, X-ray optics, X-ray detection and data acquisition. Here it is described how photon-in photon-out hard X-ray spectroscopy techniques can be applied to study the electronic structure and its dynamics of transition metal systems with ultra-bright and ultra-short FEL X-ray pulses. In particular, some of the experimental details that are different compared with synchrotron-based setups are discussed and illustrated by recent measurements performed at the Linac Coherent Light Source.

X-ray Emission Spectroscopy as an in Situ Diagnostic Tool for X-ray Crystallography of Metalloproteins Using an X-ray Free-Electron Laser

“…13, 26 The set-up used a von Hamos spectrometer 9, 27 to measure the entire Kβ 1,3 emission spectrum on a shot-by-shot basis. 9, 16, 17, 27 The signal was collected on an ePix100 detector 28 with a pixel size of 50 μm. This leads to spreading of the charge cloud generated by a single X-ray photon over multiple pixels on the detector, also referred to as ‘charge-sharing’ for single photon events.…”

“…The XES spectrometer is positioned orthogonal to the beam along the XFEL polarization direction to minimize the background from elastic scattering. 17 Such a multimodal experiment can be inefficient if the microcrystals are too small leading to an insufficient XES signal, as it is the case with the liquid microjet sample delivery systems. The DOT method overcomes this problem by ensuring a high measurement/probing efficiency and the use of larger crystal size (>20 micrometer crystals in droplets), making XES a powerful in situ diagnostic tool for XRD.…”

Ultrafast Time-Resolved Hard X-Ray Emission Spectroscopy on a Tabletop

“…However, the slicing process reduces the available x-ray flux, and we are unaware of any TRXES measurements at sliced beam lines. TRXES experiments with time resolution better than 60 ps have been performed only at the LCLS and SACLA free-electron laser facilities where sub-100-fs resolution is possible [7,[25][26][27][28]. In the laboratory, static XES measurements are possible [29][30][31][32], but measurements of ultrafast behavior have been stymied by the limited intensity of laboratory x-ray sources with suitable pulse duration and the limited collection efficiency of high-resolution x-ray spectrometers.…”

In situ/Operando studies of electrocatalysts using hard X-ray spectroscopy

“…This finding suggests that nickel ions serve as a reservoir for oxidizing equivalents, while the chemical platform for bond formation would be the manganese ions. The methodology used for this study is general and can be applied to study the reaction kinetics of materials consisting of multiple elements to follow the dynamics of catalytic and electron transfer reactions [58]. …”