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![[Figure 1]](ba5295fig1mag.jpg)
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Figure 1
(a) GDVN injecting water. The sample is pumped through the inner capillary (brown), which is centred within the flame-polished larger capillary used to transport the sheath gas. The sample jet is focused by the sheath gas through the nozzle aperture, producing a micrometre-sized jet. (b) HVE injector injecting Vaseline. Again, the sample is transported through the inner capillary (brown) and the helium-gas stream flowing out of the outer capillary directs the extruded jet. In (a) and (b) the arrow indicates the X-ray interaction. For pump–probe experiments, a section of the sample jet is optically triggered (green shading) before X-ray probing. The black scale bar is 100 µm in length. (c) Constraints on time delays for time-resolved experiments valid for any injection system. The reaction is triggered in crystals (orange) within the segment hit by the pump pulse (optical axis indicated in green) at time T0. After a time delay ΔT the X-ray pulse (purple arrow) probes one of the excited crystals (red) at time T1. The jet speed v must be sufficiently low that crystals excited within the region D upstream of the X-ray optical axis have not yet all passed through the interaction region (dashed line), i.e. v < D/ΔT. All crystals triggered at T0 must clear the interaction region before the arrival of the subsequent probe pulse at T = ΔT + τ, where 1/τ is the X-ray repetition rate, requiring the jet speed to be v > D/(τ + ΔT). This figure was adapted from Grünbein (2017  ). |
![[Figure 1]](ba5295fig1.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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