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Related LCLS time-resolved soft X-ray spectroscopy studies of metalloproteins and metal complexes, in solution and at room temperature, demonstrate the power of these methods for mapping changes in valence electronic structure (e.g. oxidation state, charge and spin densities) of catalytically-active metal centers in (bio) chemical reactions under functioning conditions.2 Ultrafast X-rays not only enable capturing transient states in reactive systems, but also avoid “X-ray damage”, i.e. subtle X-ray induced redox changes that are a significant issue for conventional X-ray studies, often limiting measurements to fixed robust samples at cryogenic temperatures.
Photocathodes can be metals, semi-conductors and even diamonds. One of the most important properties is that the electrons are emitted only when the laser pulse is applied – this makes the device very efficient compared to older style sources and allows us to easily synchronize the pulses to match the frequency of the accelerator. Using RF (radio-frequency) to accelerate the electrons instead of DC (static voltage) permits much higher accelerating gradients and higher final energy out of the electron gun. The combination of a photocathode with high accelerating fields enables us to produce very high brightness electron beams. Both LCLS-I and LCLS-II use copper RF guns as their electron source.
Related LCLS time-resolved soft X-ray spectroscopy studies of metalloproteins and metal complexes, in solution and at room temperature, demonstrate the power of these methods for mapping changes in valence electronic structure (e.g. oxidation state, charge and spin densities) of catalytically-active metal centers in (bio) chemical reactions under functioning conditions.2 Ultrafast X-rays not only enable capturing transient states in reactive systems, but also avoid “X-ray damage”.
