Figure 2.
(A) Solid Line: Cobalt M2,3-edge X-ray absorption (XAS) spectrum of KCoF3 measured in TEY mode at MERLIN beamline at the ALS. Line and markers: Intensity of the diffuse elastic line measured at FERMI as a function of incoming photon energy. Each point represents the total number of counts measured by the CCD detector averaged over 1000 FEL shots, while the FEL photon energy was varied via an automatized scanning procedure. The gap between 59 eV and 61 eV in the RXES curve is caused by the switching of seed harmonics where the automatized procedure for FEL tuning has not been optimized to deliver X-rays. The data have been normalized by the incoming photon flux, which is determined by measuring the shot-by-shot current on the last TIMEX beamline mirror (ellipsoidal), taking into account the energy-dependent reflectivity of the back-reflecting mirror included in the RIXS setup. The red and black squares mark the two photon energies at which the RIXS signal has been measured. Dashed red curve: Reflectivity of back-reflecting refocusing multilayer mirror as a function of incoming photon energy. The reflectivity shown is from the center of the mirror but is uniform across the mirror. (B) RIXS spectra measured at MERIXS (solid lines) and at FERMI (lines and dots) at two excitation energies 61.0 eV (red) and 62.5 eV (black). The resonating d-d transition (solid arrow) at about 1 eV can be identified in both measurements despite the different energy resolution of these two measurements.