FIG. 3.

Schematic representation of the experimental setup. A ∼100 μm thick liquid jet of the sample (a solution of ∼5.6 mM MbCO in 0.1 M phosphate buffer at pH 7.4, in red) was produced with a homemade nozzle. The sample was photoexcited with ∼70 fs optical laser pulses at 538 nm (green beam) and probed with ∼30 fs monochromatic X-ray pulses (white beam) in nearly collinear (∼1°) geometry (the angle between the pump and the probe beams is exaggerated in the figure for the sake of clarity). The large offset monochromator of XPP is sketched in white (Zhu et al., 2012). An X-ray diode (in blue) was used to measure the total fluorescence yield signal as a function of the delay between pump and probe pulses.