Mattis Fondell, Sebastian Eckert, Raphael Martin Jay, Christian Weniger, Wilson Quevedo, Johannes Niskanen, Brian Kennedy, Florian Sorgenfrei, Daniel Schick, Erika Giangrisostomi, Ruslan Ovsyannikov, Katrin Adamczyk, Nils Huse, Philippe Wernet, Rolf Mitzner, Alexander Föhlisch

• We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II)-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime. In combination with the wavelength tunability of the laser system, the set-up opens up opportunities to study the photochemistry of many systems at low concentrations, relevant to materials sciences, chemistry, and biology.