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

• 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. (C) 2016 Optical Society of America