An international team of scientists has made a surprising discovery in the field of molecular physics, revealing unexpected symmetry breaking dynamics in carbon dioxide dimers after ionization. The study, published in Nature Communications, provides new insights into the structural changes that occur when these molecular aggregates are exposed to extreme ultraviolet (EUV) radiation.
An international team of scientists, led by Professors Daniel Strasser and Roy Baer from the Hebrew University of Jerusalem, made an important discovery in the field of molecular physics, revealing unexpected symmetry breaking dynamics in carbon dioxide dimers after ionization. Dimers of CO₂ molecules after ionization is a situation where a pair of carbon dioxide (CO₂) molecules are united to form a double molecular structure called a dimer, and undergo an ionization process.
The study, published in Nature Communications, reveals new insights into the structural changes that occur when these molecular aggregates are exposed to extreme ultraviolet (EUV) radiation. The joint effort demonstrated that ionized CO₂ dimers undergo asymmetric structural rearrangement, leading to the formation of CO₃ units. This discovery has significant implications for atmospheric chemistry and astrochemistry, offering a deeper understanding of molecular behavior under extreme conditions.
Key findings: dynamics of symmetry breaking and structural organization
In environments such as cold outer space and atmospheric environments, carbon dioxide molecules tend to form symmetric pairs. According to quantum mechanics, the wave function of these pairs should preserve symmetry even after ionization. However, researchers from the Hebrew University of Jerusalem (Israel), from the Max Planck Institute for Nuclear Physics (Germany), and from the FLASH free electron laser facility at DESY (Germany) observed a phenomenon called symmetry breaking.
Two established models of quantum chemistry were used to predict the behavior of the ionized dimers. The first model proposed that the molecules would move in unison, maintaining their symmetrical shape. In contrast, the second model predicted that the ionization would break the symmetry, causing one of the molecules to rotate slowly around an axis and point towards its partner in about 150 femtoseconds. Using fast EUV pulses produced by the FLASH free electron laser, the researchers confirmed the second model, showing that the ionized dimers do undergo asymmetric structural organization.
This symmetry breaking leads to the formation of CO₃ units, which may play a critical role in the chemical evolution of more complex species in cold outer space environments.
Quantum mechanics and the symmetry breaking phenomenon
A central question that arises from the research is how symmetry breaking occurs even though quantum mechanics forbids it. The researchers explain that, similar to the famous Schrödinger's cat, the pair of carbon dioxide molecules exists in a superposition of two states of symmetry breaking. The system maintains symmetry until the quantum wave function collapses during measurement, which leads to one of the CO₂ molecules rotating relative to the other.
Broad implications and future research
Prof. Daniel Strasser, lead author of the study, emphasized the importance of the findings: "Our study demonstrates the power of combining advanced experimental techniques with advanced theoretical models to reveal unexpected molecular behavior. These insights into the dynamics of carbon dioxide ionizing dimers may open new ways of carbon dioxide chemistry and contribute to our understanding of planetary and atmospheric processes."
Prof. Roi Beer, who led the theoretical model, added: "By directly comparing theory with experimental measurements, we improve our ability to simulate and predict the results of chemical reactions that occur in remote environments and are not possible to test experimentally in the laboratory."
The results of the research include significant implications for atmospheric chemistry, astrochemistry, and provide new insights into the atmospheric carbon dioxide cycle. The discovery of the asymmetric structural organization, the formation of the CO₃ unit, and timed dynamics provide a deeper understanding of molecular processes under extreme conditions.
The research was made possible thanks to international cooperation and the use of the most advanced facilities, including the FLASH2 free electron laser at DESY in Hamburg, Germany. The team's innovative approach paves the way for further investigations into the behavior of molecular aggregates under extreme conditions, with potential applications from the field of atmospheric science to new chemical synthesis methods.
Clip: The movie shows a simulation of CO₂ dimer dynamics activated by photoionization. The release of the kinetic energy (KER) in the colon explosion of the dimer by a time-delayed pulse made it possible to test the dynamics experimentally.
