Figure 10.

(A) Schematic for the crystal monochromator used in a backscattering configuration. (B) Left: X-ray fluorescence of Mn and Fe. Above: Mn Kα₁ and Kα₂ fluorescence peaks, with a natural line width of ~5 eV, split by 11 eV. The multicrystal monochromator with 1 eV resolution is tuned to the Mn Kα₁ peak (red spectrum). Below: fluorescence peaks of Mn and Fe as detected using a Ge detector. The fluorescence peaks are convoluted with the electronic window resolution of 150–200 eV of the Ge detector (black and green spectra for Mn and Fe fluorescence). This method of detection cannot resolve Mn Kα₁ and Kα₂ fluorescence peaks. Note different energy scales for the schemes are shown above and below. Iron is an obligatory element in functional PS II complexes. Right: Comparison of the PS II Mn K-edge EXAFS spectrum from an S₁ state PS II sample obtained with a traditional 30-element energy-discriminating Ge detector with a spectrum collected using the high-resolution crystal monochromator. Use of the high-resolution detector eliminates the interference of Fe and removes the limit of the energy range for Mn EXAFS data collection.