Auburn chemist is computational chemist lead on research featured in "Science"
Evangelos Miliordos, associate professor and a computational chemist at Auburn University whose research focuses on the electronic properties of metal ammonia complexes, is part of an international collaboration with six experimental chemists from ETH Zurich, University of Freiburg and Synchrotron SOLEIL in France that was published in the prestigious journal Science on May 25, 2023.
“I am extremely proud that research from faculty in the Department of Chemistry and Biochemistry directly contributed to a publication in ‘Science,’ a journal that has immense impact,” said Doug Goodwin, chair of the department. “Because they publish only six percent of the manuscripts they receive each year, Evangelos has marked a significant career achievement to see his work emerge in this journal.”
As the lead computational chemist on the research project, Solvated dielectrons from optical excitation: An effective source of low-energy electrons, Miliordos was able to use theory to explain why electrons were emitted at a much slower speed than anticipated from the process creating the first dielectron shown in a gas phase.
“Theory can explain experiments that have been conducted and guide future experimental studies,” said Miliordos. “Our research used photoelectron spectroscopy to shine light in sodium-ammonia coordination complexes where the first thing that happens during the experiment is ionization of the complex and ejection of an electron.”
Normally, these electrons come out fast, full of kinetic energy.
“Now, imagine that you shine light at a considerably higher frequency (UV) light. You would expect the electron to come out even faster,” he said.
But that was not the case in the actual experiment.
“Instead, slow electrons were emitted from the molecular complex,” he explained.
The calculations gave insight as to why the speed was drastically different for the electron leaving. Electron-Transfer-Mediated Decay (ETMD) was the key factor to explain the process.
“Instead of light kicking out the electron and making it move fast, one electron was moved from ammonia to the existing solvated electron making a solvated dielectron,” he said. “This is the very first time that we can detect a dielectron.”
“During the experiment, the dielectron eventually decomposes and one electron returns to ammonia while the other electron does not have much energy remaining, so it exits very slowly. Theory showed that ETMD can only be observed if you already have one solvated electron and thus can be utilized to identify solvated electrons” Miliordos said.
“The experiment can be conducted with any alkali metal but requires a highly polar solvent such as water or ammonia,” Miliordos added. “A less polar or non-polar solvent will not work.”
Slow electrons play a role in DNA damage and this work shows a possible way that these can be produced. Real-world applications involve more controlled radiation chemistry.
“With a slower pace, the electron can be captured by a nearby molecule and there is a higher chance for subsequent targeted reactions,” he said. “This experiment opened up a new avenue for future uses of solvated electrons.”
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