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![[Figure 7]](hi2039fig7mag.jpg)
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Figure 7
Experimental setup to drive the PSII through its catalytic cycle by applying nanosecond laser pulses at the beamline. Laser-flash excitation of the samples was performed at the beamline ID26 (ESRF, Grenoble) using a frequency-doubled Q-switched Nd-YAG laser (Quantel Brilliant, FWHM 5 ns, 532 nm, ca. 150 mJ per flash). The laser beam was widened by lenses to a spot size of ca. 20 × 8 mm. Half of the spot illuminated the front-side of the sample directly. The other half was reflected by a mirror to the back-side of the sample. This setup ensured simultaneous and homogenous illumination of the sample from both sides. A chromium filter and a thin aluminium foil in front of the photodiode suppressed scattered X-rays and laser light, respectively. The absorption spectrum of KMnO4 was measured to facilitate a precise energy calibration. To minimize X-ray exposure times (radiation damage), a rapid beam shutter was used that opened only immediately before the start of theX-ray measurements. The rapid beam shutter, laser flashes, and data acquisition were synchronized using appropriate trigger electronics. |
![[Figure 7]](hi2039fig7.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
