Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 112: Development of Novel Methods I
O 112.2: Talk
Thursday, March 19, 2020, 15:30–15:45, WIL C107
X-Ray Absorption Spectroscopy at Free-Electron Lasers using a Split-Beam Referencing Scheme — •Robin Y. Engel1,3, Günter Brenner1, Siarhei Dziarzhytski1, Piter S. Miedema1, Jan Schunck1,3, Florian Döring2, Benedikt Rösner2, Christian David2, and Martin Beye1 — 1Deutsches Elektronen Synchrotron DESY, Germany — 2Paul Scherrer Institut, Switzerland — 3Universität Hamburg, Germany
Any absorption spectroscopy is based on the exact measurement of the ratio between incident and transmitted intensity. If the used light-source provides a constant incident intensity, measuring only the transmitted light can be sufficient. In order to measure X-ray Absorption Spectra (XAS) with a time-resolution on the fs-scale, X-ray sources with high brilliance and short pulse duration are required. Modern Free Electron Lasers (FEL) deliver such pulses, but most exhibit a strongly fluctuating spectral content, so that an exact measurement of both incident and transmitted intensities becomes necessary. This can be achieved using a diffraction grating in transmission that splits the FEL beam into two identical copies (+/- 1. diffraction order) which are used as probe- and reference-beams. For ideal comparability, both beams are measured on the same CCD-detector after one of them has interacted with the sample. This concept was implemented at the Free Electron LASer in Hamburg (FLASH) both in transmission and reflection geometries. X-ray absorption spectra can be recorded either in monochromatic mode, or by directly normalizing two copies of an energy-dispersed beam on the same CCD.