Parallel Broadband Femtosecond Reflection Spectroscopy at a Soft X-Ray Free-Electron Laser

Applied Sciences

Diego Turenne¹  HermannA. Dürr¹  Igor Vaskivskyi¹  JanO. Schunck²  Marion Kuhlmann²  PiterS. Miedema²  Martin Beye²  RobinY. Engel²  Günter Brenner²  Siarhei Dziarzhytski²  Christian Schüßler-Langeheine³  StuartS.P. Parkin⁴  Andriy Styervoyedov⁴  Christian David⁵  Florian Döring⁵ 

[1] Department of Physics and Astronomy, Uppsala University, S-75120 Uppsala, Sweden;Deutsches Elektronen Synchrotron, 22607 Hamburg, Germany;Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany;Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, 06108-06132 Halle, Germany;Paul Scherrer Institut, 5232 Villigen-PSI, Switzerland;

关键词: X-ray absorption spectroscopy;    free electron laser;    intensity normalization;    transmission grating;    X-ray reflectivity;   

DOI  :  10.3390/app10196947

来源: DOAJ

【 摘 要 】

X-ray absorption spectroscopy (XAS) and the directly linked X-ray reflectivity near absorption edges yield a wealth of specific information on the electronic structure around the resonantly addressed element. Observing the dynamic response of complex materials to optical excitations in pump–probe experiments requires high sensitivity to small changes in the spectra which in turn necessitates the brilliance of free electron laser (FEL) pulses. However, due to the fluctuating spectral content of pulses generated by self-amplified spontaneous emission (SASE), FEL experiments often struggle to reach the full sensitivity and time-resolution that FELs can in principle enable. Here, we implement a setup which solves two common challenges in this type of spectroscopy using FELs: First, we achieve a high spectral resolution by using a spectrometer downstream of the sample instead of a monochromator upstream of the sample. Thus, the full FEL bandwidth contributes to the measurement at the same time, and the FEL pulse duration is not elongated by a monochromator. Second, the FEL beam is divided into identical copies by a transmission grating beam splitter so that two spectra from separate spots on the sample (or from the sample and known reference) can be recorded in-parallel with the same spectrometer, enabling a spectrally resolved intensity normalization of pulse fluctuations in pump–probe scenarios. We analyze the capabilities of this setup around the oxygen K- and nickel L-edges recorded with third harmonic radiation of the free electron laser in Hamburg (FLASH), demonstrating the capability for pump–probe measurements with sensitivity to reflectivity changes on the per mill level.

【 授权许可】

Unknown