A team with participation from the University of Freiburg generates low-energy electrons using ultraviolet light. Freiburg, May 26, 2023
Solvated dielectrons are the subject of many hypotheses among scientists, but have never been directly observed. They are a pair of electrons dissolved in liquids such as water or liquid ammonia. A cavity forms in the liquid, which the two electrons occupy. An international research team led by Dr. Sebastian Hartweg, originally at the SOLEIL synchrotron in France and now at the Physics Institute of the University of Freiburg, and Prof. Dr. Ruth Signorell of ETH Zurich, with the participation of scientists from the SOLEIL synchrotron and Auburn University (USA), has now succeeded in discovering a formation and decay process of the solvated dielectron: In experiments at the SOLEIL synchrotron, supported by quantum chemical calculations, the team found direct evidence for the formation of these electron pairs through ultraviolet light excitation in tiny ammonia droplets containing a single sodium atom. The results have been published in the journal Science.
Traces of an Unusual Process
When dielectrons form through ultraviolet light excitation in ammonia droplets containing a sodium atom, they leave their traces in an unusual process that the scientists have now observed for the first time. One of the two electrons migrates to the surrounding solvent molecules, while the other electron is simultaneously ejected. “The astonishing thing is that similar processes have so far been observed mainly at significantly higher excitation energies,” says Hartweg. The team focused on this second electron because it could have interesting applications. Firstly, the ejected electron is generated with very low kinetic energy, meaning it moves very slowly. Secondly, this energy can be controlled via the irradiated UV light that initiates the entire process. Solvated dielectrons could therefore serve as a good source of low-energy electrons.
Specifically generated with variable energy
Such electrons can initiate a wide variety of chemical processes. For example, they play a role in the cascade of processes that lead to radiation damage in biological tissue. They are also important in synthetic chemistry, where they serve as effective reducing agents. By now being able to specifically generate these electrons with variable energy, the mechanisms of such chemical processes can be studied in more detail in the future. Furthermore, the controlled energy provided to the electrons could also be used to increase the effectiveness of reduction reactions. “These are interesting prospects for possible future applications,” says Hartweg. “Our work provides the foundation for this and contributes to a better understanding of these exotic and still enigmatic solvated dielectrons.”
Fact sheet:
Original publication: S. Hartweg, J. Barnes, B. L. Yoder, G. A. Garcia, L. Nahon, E. Miliordos, R. Signorell: Solvated dielectrons from optical excitation: An effective source of low-energy electrons, Science 0, eadh0184. DOI: https://doi.org/10.1126/science.adh0184
Dr. Sebastian Hartweg is a research associate at the Physics Institute of the University of Fribourg. His research focuses on the electronic structure and dynamics of molecules and molecular clusters. Prof. Dr. Ruth Signorell heads the Aerosols and Nanoscience research group at ETH Zurich. In addition to the University of Freiburg and ETH Zurich, the SOLEIL synchrotron in Saint-Aubin, France, and Auburn University, USA, were involved in the work.
The project was funded by the European Union’s Horizon 2020 research and innovation program of the European Research Council under grant agreement 786636, the Swiss National Science Foundation (project 200020_200306), and the United States National Science Foundation (Grant No. CHE-1940456).
Contact:
Hochschul- und Wissenschaftskommunikation
Universität Freiburg
Tel.: 0761/203-4302
E-Mail: kommunikation@zv.uni-freiburg.de
