Researchers Achieve Controlled Generation of Slow Electrons in a Liquid Medium

The following image portrays two electrons briefly associating as a dielectron (coloured red) within a sea of solvent molecules. The precise location of the dielectron is indeterminable. Ultimately, one of the electrons will vacate this region. Image credit: Hartweg S et al. Science 2023

A team of scientists from around the globe has successfully engineered the production of slow-moving electrons in a solution, a breakthrough that could potentially optimize certain chemical reactions in the future.

The main objective of this international research collaboration was to detect an elusive chemical entity, known as a dielectron, in solution. A dielectron is a transient entity composed of two electrons, which, unlike an atom, lacks a nucleus. Thus far, the direct detection of such an entity has remained beyond the grasp of scientific endeavors.

While conducting experiments involving dielectrons, a serendipitous discovery was made by the team, led by Professor Ruth Signorell from ETH Zurich, unveiling a novel process for generating slow electrons. Such electrons hold promise in initiating certain chemical reactions.

Dielectrons are inherently unstable. They rapidly dissociate back into two separate electrons in less than a trillionth of a second. As illustrated by the team’s findings, one of the electrons stays put, while the other, with lower energy and consequently slower velocity, moves away. This newly discovered method is unique in its ability to regulate the kinetic energy, and thus the speed, of the departing electron.

Producing dielectrons involves first dissolving sodium in liquid ammonia and subsequently irradiating the solution with UV light. This results in an electron from an ammonia molecule associating with an electron from a sodium atom to form a dielectron. This dielectron temporarily occupies a minuscule cavity in the solution. The researchers demonstrated that the speed of the departing electron upon dielectron dissociation can be controlled by the UV light’s wavelength. “A fraction of the UV light’s energy gets transferred to the electron,” explains Signorell.

The research effort was a joint venture between the ETH Zurich team and scientists from the University of Freiburg, Germany, the SOLEIL synchrotron in France, and Auburn University, USA.

The study of such low-kinetic-energy electrons is beneficial for several reasons. Notably, slow-moving electrons contribute to radiation-induced damage to human tissues. These mobile electrons, which can result from exposure to X-rays or radioactivity, can bind to DNA molecules, triggering chemical reactions. By more easily generating these slow electrons in a laboratory setting, researchers can more accurately investigate the underlying mechanisms causing radiation damage.

However, chemical reactions aren’t only induced by free electron acceptance within the human body. The synthesis of synthetic cortisone and various other steroids is one such instance.

Using UV light as a straightforward method to produce and control the energy of slow electrons directly in a solution will simplify the investigation of these reactions in future studies. It might even enable chemists to fine-tune reactions, such as employing UV light to amplify the kinetic energy of electrons.

Reference: “Solvated dielectrons from optical excitation: An effective source of low-energy electrons” by Sebastian Hartweg, Jonathan Barnes, Bruce L. Yoder, Gustavo A. Garcia, Laurent Nahon, Evangelos Miliordos, and Ruth Signorell, 25 May 2023, Science.
DOI: 10.1126/science.adh0184

Frequently Asked Questions (FAQs) about Slow Electrons Production

More about Slow Electrons Production

• Dielectrons: A basic overview
• ETH Zurich: Institute of Molecular Science and Engineering
• University of Freiburg: Faculty of Chemistry and Pharmacy
• SOLEIL Synchrotron: Research Facility
• Auburn University: Department of Chemistry and Biochemistry
• The Role of Electrons in Chemical Reactions
• Radiation Damage to Human Tissue
• Steroids Synthesis