LED-pump-X-ray-multiprobe crystallography for sub-second timescales

Time-resolved single-crystal X-ray diffraction experiments largely focus on timescales shorter than microseconds, whereby slower population dynamics are missed. Here, the authors resolve the 3D structures of photoexcited solid-state species with millisecond-to-minute lifetimes using pump-multiprobe SCXRD. The visualization of chemical processes that occur in the solid-state is key to the design of new functional materials. One of the challenges in these studies is to monitor the processes across a range of timescales in real-time. Here, we present a pump-multiprobe single-crystal X-ray diffraction (SCXRD) technique for studying photoexcited solid-state species with millisecond-to-minute lifetimes. We excite using pulsed LEDs and synchronise to a gated X-ray detector to collect 3D structures with sub-second time resolution while maximising photo-conversion and minimising beam damage. Our implementation provides complete control of the pump-multiprobe sequencing and can access a range of timescales using the same setup. Using LEDs allows variation of the intensity and pulse width and ensures uniform illumination of the crystal, spreading the energy load in time and space. We demonstrate our method by studying the variable-temperature kinetics of photo-activated linkage isomerism in [Pd(Bu(4)dien)(NO2)][BPh4] single-crystals. We further show that our method extends to following indicative Bragg reflections with a continuous readout Timepix3 detector chip. Our approach is applicable to a range of physical and biological processes that occur on millisecond and slower timescales, which cannot be studied using existing techniques.

Automated summary

The authors developed a pump-multiprobe single-crystal X-ray diffraction technique to study the 3D structures of photoexcited solid-state species with millisecond-to-minute lifetimes. This method allows real-time monitoring of chemical processes and has potential applications in the design of new functional materials.