X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser.

Thomas Kröll ,Stefan Moeller,Roberto Alonso-Mori,Raymond G Sierra,Jens Rehanek,Daniel Ratner,Alexei Erko,Hartawan Laksmono,Yuantao Ding,Vittal K Yachandra,Markus Kubin,Alexander Föhlisch,Joshua J Turner,Georgi L Dakovski,Alberto Lutman,Junko Yano,Jan Kern,Christian Weniger,Sheraz Gul,Philippe Wernet,Ruchira Chatterjee,Uwe Bergmann,Heike Löchel,Franklin D Fuller,Alexander A Firsov ,Ethan A Hill ,Benedikt Lassalle‐Kaiser ,Dennis Nordlund ,J Krzywiński ,R Mitzner ,A S Borovik ,M M Brzhezinskaya

doi:10.1364/oe.24.022469

Abstract

X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements.

Highlights

X-ray Free Electron Lasers (XFELs) are unique sources for the study of electronic and atomic structure and dynamics, dramatically extending the capabilities of synchrotron radiation (SR) sources, which have been at the center of such studies over the past several decades [1]
We compare L-edge xray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the spontaneous emission (SASE) radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS
With XAS at the L absorption edge of a dilute solution of a 3d transition metal Mn sample, we address in detail the influence of changes in resolving power, wavelength stability, peak and average flux when going from SASE to the self-seeded mode

Summary

Introduction

X-ray Free Electron Lasers (XFELs) are unique sources for the study of electronic and atomic structure and dynamics, dramatically extending the capabilities of synchrotron radiation (SR) sources, which have been at the center of such studies over the past several decades [1]. Prominent examples in the soft x-ray regime are 3d transition metal L-edge and ligand K-edge XAS, with their high sensitivity to oxidation and spin states, and the potential to extract the order of orbital energy levels, the symmetry and the covalency of the studied complexes [14,15,16,17,18,19] These methods have been successfully applied to date at synchrotrons, and they are being established at XFELs to investigate ultrafast dynamics in chemical reactions on surfaces [20,21,22,23], in liquids [3,4,24,25] and gases [26].

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Results

Conclusion