Spectroscopy expert Felix Allum from Stanford University will use DESY’s free-electron laser FLASH for time-resolved X-ray spectroscopic investigations of the dynamics of organic photochemical reactions with potential synthetic applications. He comes to Hamburg through a Humboldt Research Fellowship, a funding programme offered by the Alexander von Humboldt Foundation for international researchers to conduct long-term research projects in Germany.

The high-intensity, ultrashort pulses of soft X-ray light produced by the free-electron laser FLASH can be used to study the rearrangement of electrons and nuclei within molecules as the undergo photochemical reactions – chemistry triggered by the absorption of light, aka photochemistry. Photochemistry forms the basis of many important processes from energy harvesting to protecting biological organisms from the potentially harmful effects of sunlight. Over the past several years, Felix Allum has been involved in a number of experiments that study these processes at FLASH both during his PhD in Physical Chemistry at the University of Oxford and as postdoctoral research at Stanford University.

 

Now, Allum will join the team at FLASH to pursue an independent research project funded by a prestigious Alexander von Humboldt Fellowship, which lasts for two years. He will investigate photochemical reactions with potential applications in organic synthesis. “There’s great potential in using light-induced reactions in the synthesis of the chemicals that are essential for modern technologies and medicines. Particularly given the ongoing climate crisis, we can potentially circumvent the substantial energy costs associated with heating, by instead triggering desired chemistry with light – developing ‘greener’ synthetic strategies,” explains Allum. “When a molecule absorbs light, however, a number of competing reactions may be possible. Typically, we cannot predict for a given molecule whether it will follow the synthetically desirable reaction, or some unwanted side reaction. For full synthetic exploitation of photochemistry, we need a better fundamental understanding.”

 

To develop this fundamental understanding, Allum will use time-resolved X-ray spectroscopies at FEL facilities such as FLASH. Optical spectroscopies have long been used to probe photochemical reaction dynamics, but as the researcher explains, extending these techniques into the X-ray regime can enable entirely new insights. “As we enter the X-ray regime, we access spectroscopic transitions associated with specific atomic sites within a molecule. This allows us to track the local flow of electron density within a photoexcited molecule, which ultimately directs the nuclear dynamics that brings about photochemistry, producing new product species. This information can’t be directly accessed by traditional spectroscopic techniques that use visible or ultraviolet light.” 

 

During his Humboldt fellowship, Allum will work closely with the research group of Markus Gühr, Lead Scientist at FLASH and Professor of Chemistry at the University of Hamburg. “I’m extremely excited to be working with Prof. Gühr’s team,” says Allum. “The research infrastructure and expertise they’ve built up at FLASH is truly world-leading, and I very much looking forward to benefitting from this.” The FLASH2020+ upgrades the facility is currently undergoing will also be very advantageous for Allum’s research because it widens the range of photon energies accessible and improves the experimental resolutions that can be achieved.