MSGID: 1:317/3 6455d7f8   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Scientists capture elusive chemical reaction using enhanced X-ray method   
      
      
     Date:   
         May 5, 2023   
     Source:   
         DOE/SLAC National Accelerator Laboratory   
     Summary:   
         Researchers have captured one of the fastest movements of a molecule   
         called ferricyanide for the first time by combining two ultrafast   
         X-ray spectroscopy techniques. They think their approach could help   
         map more complex chemical reactions like oxygen transportation in   
         blood cells or hydrogen production using artificial photosynthesis.   
      
      
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   FULL STORY   
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   Researchers at SLAC National Accelerator Laboratory captured one of   
   the fastest movements of a molecule called ferricyanide for the first   
   time by combining two ultrafast X-ray spectroscopy techniques. They   
   think their approach could help map more complex chemical reactions   
   like oxygen transportation in blood cells or hydrogen production using   
   artificial photosynthesis.   
      
   The research team from SLAC, Stanford and other institutions started   
   with what is now a fairly standard technique: They zapped a mixture   
   of ferricyanide and water with an ultraviolet laser and bright X-rays   
   generated by the Linac Coherent Light Source (LCLS) X-ray free-electron   
   laser. The ultraviolet light kicked the molecule into an excited state   
   while the X-rays probed the sample's atoms, revealing features of   
   ferricyanide's atomic and electronic structure and motion.   
      
   What was different this time is how the researchers extracted   
   information from the X-ray data. Instead of studying only one   
   spectroscopic region, known as the Kb main emission line, the team   
   captured and analyzed a second emission region, called valence-to-core,   
   which has been significantly more challenging to measure on ultrafast   
   timescales. Combining information from both regions enabled the team   
   to obtain a detailed picture of the ferricyanide molecule as it evolved   
   into a key transitional state.   
      
   The team showed that ferricyanide enters an intermediate, excited state   
   for about 0.3 picoseconds -- or less than a trillionth of a second --   
   after being hit with a UV laser. The valence-to-core readings then   
   revealed that following this short-lived, excited period, ferricyanide   
   loses one of its molecular cyanide "arms," called a ligand. Ferricyanide   
   then either fills this missing joint with the same carbon-based ligand   
   or, less likely, a water molecule.   
      
   "This ligand exchange is a basic chemical reaction that was thought to   
   occur in ferricyanide, but there was no direct experimental evidence of   
   the individual steps in this process," SLAC scientist and first author   
   Marco Reinhard said.   
      
   "With only a Kb main emission line analysis approach, we wouldn't really   
   be able to see what the molecule looks like when it is changing from   
   one state to the next; we'd only obtain a clear picture of the beginning   
   of the process."  "You want to be able to replicate what nature does to   
   improve technology and increase our foundational scientific knowledge,"   
   SLAC senior scientist Dimosthenis Sokaras said. "And in order to better   
   replicate natural processes, you have to know all of the steps, from the   
   most obvious to those that happen in the dark, so to speak."  In the   
   future, the research team wants to study more complex molecules, such   
   as hemeproteins, which transport and store oxygen in red blood cells --   
   but which can be tricky to study because scientists do not understand   
   all the intermediate steps of their reactions, Sokaras said.   
      
   The research team refined their X-ray spectroscopy technique at SLAC's   
   Stanford Synchrotron Radiation Lightsource (SSRL) and the LCLS over   
   many years, and then combined all this expertise at the LCLS's X-ray   
   Correlation Spectroscopy (XCS) instrument to capture the molecular   
   structural changes of ferricyanide. The team published their results   
   today in Nature Communications.   
      
   "We leveraged both SSRL and LCLS to complete the experiment. We couldn't   
   have finished developing our method without access to both facilities   
   and our longstanding collaboration together," said Roberto Alonso-Mori,   
   SLAC lead scientist. "For years, we have been developing these methods   
   at these two X-ray sources, and now we plan to use them to uncover   
   previously inaccessible secrets of chemical reactions."   
       * RELATED_TOPICS   
             o Matter_&_Energy   
                   # Detectors # Optics # Organic_Chemistry # Chemistry #   
                   Inorganic_Chemistry # Physics # Electronics # Biochemistry   
       * RELATED_TERMS   
             o Autocatalysis o Spectroscopy o Positron_emission_tomography   
             o Oxygen o Carbon_dioxide o Carbohydrate o Combustion o   
             Tissue_engineering   
      
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   Story Source: Materials provided by   
   DOE/SLAC_National_Accelerator_Laboratory. Original written by David   
   Krause. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Marco Reinhard, Alessandro Gallo, Meiyuan Guo, Angel   
      T. Garcia-Esparza,   
         Elisa Biasin, Muhammad Qureshi, Alexander Britz, Kathryn Ledbetter,   
         Kristjan Kunnus, Clemens Weninger, Tim van Driel, Joseph Robinson,   
         James M. Glownia, Kelly J. Gaffney, Thomas Kroll, Tsu-Chien   
         Weng, Roberto Alonso-Mori, Dimosthenis Sokaras. Ferricyanide   
         photo-aquation pathway revealed by combined femtosecond Kb main   
         line and valence-to-core x-ray emission spectroscopy. Nature   
         Communications, 2023; 14 (1) DOI: 10.1038/ s41467-023-37922-x   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230505141356.htm   
      
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