China News Service, Beijing, February 16 (Reporter Sun Zifa) Is there a roaming reaction when a molecule reaches a highly excited state? The latest news from the Chinese Academy of Sciences says that Chinese scientists have discovered the first roaming reaction channel in a highly excited state of a molecule through their latest research, giving a definite answer. This not only demonstrates the universality of the roaming reaction mechanism in chemical reactions, but also provides a new perspective for understanding and predicting chemical reactions.
This important research confirming the existence of roaming reactions in highly excited states of molecules was completed by the experimental team of researcher Yuan Kaijun and academician Yang Xueming of the Dalian Institute of Chemical Physics (Dalian Institute of Chemical Physics) of the Chinese Academy of Sciences (Dalian Institute of Chemical Physics), and the theoretical team of researcher Fu Bina and academician Zhang Donghui, using the Dalian Coherent Light Source, Beijing On February 16, the relevant results paper was published in the internationally renowned academic journal "Science".
A schematic poster showing the scientific research results of Chinese scientists who "discovered the first example of a highly excited molecular roaming reaction channel". Dalian Institute of Chemistry, Chinese Academy of Sciences/Photo provided
What is roaming response?
According to popular science interpretation by the scientific research team of Dalian Institute of Chemical Physics, Chinese Academy of Sciences, the occurrence of chemical reactions is like "climbing over mountains and ridges". Molecules and atoms need to climb the "high mountain" of energy barriers like "climbers" before they can be converted into new substances. In the traditional transition state theory of chemical reactions, reactions mainly proceed along the path of minimum energy, just like "climbers" usually find the lowest ridgeline to cross the mountain in order to consume the least energy.
In some chemical reactions, molecules may "wrap away" from the outside of the mountain. From a microscopic perspective, atoms or groups will not be immediately disconnected from the molecule, but will "slosh" near the molecule, sometimes far and sometimes near. Just like astronauts "roaming" in space, products that are different from traditional chemical reactions are eventually formed. This is the roaming reaction.
Among chemical reactions, wandering reactions, as a special type of reaction mechanism, have also attracted widespread attention from scientists. At the beginning of the 21st century, scientists discovered the wandering response for the first time. Since then, the analysis of roaming reaction mechanisms has been limited to the low electronic states and ground states of molecules. Since molecules can only reach highly excited states by absorbing high-energy photons of extreme ultraviolet light, and high-brightness, tunable extreme ultraviolet light sources are in short supply, whether there is a wandering reaction when molecules reach highly excited states has not been confirmed.
How to conduct experimental research?
In this study, the emergence of Dalian coherent light source solved the above problems. The scientific research team of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, said that the Dalian Coherent Light Source is China's first extreme ultraviolet free electron laser developed by the team in conjunction with the Shanghai Institute of Applied Physics. It is also the world's only free electron laser user device operating in the extreme ultraviolet band. The Dalian Coherent Light Source outputs extreme ultraviolet light with high brightness and tunable wavelength, which can excite any molecule to a specific highly excited state.
The experimental team of Researcher Yuan Kaijun and Academician Yang Xueming has been engaged in research on molecular photochemical reactions for many years, and they always firmly believe that molecules have wandering reactions in highly excited states. Yuan Kaijun said that when developing the Dalian Coherent Light Source, the experimental team independently planned several research directions in advance, and interstellar molecular photochemistry was one of them. It can be said that the Dalian Coherent Light Source opened the door to the study of highly excited state reaction mechanisms of molecules.
The experimental team used the Dalian Coherent Light Source to prepare highly excited sulfur dioxide molecules, and combined it with self-developed high-resolution ion imaging technology to detect the quantum state distribution of excited oxygen products. Experiments have found that the excited state oxygen product produced by the dissociation of sulfur dioxide molecules near the 133 nm band exhibits two vibrational quantum state distributions.
How to verify theory with experiment?
After experimentally discovering the first roaming reaction channel in a highly excited state of a molecule, the theoretical team of researcher Fu Bina and academician Zhang Donghui immediately carried out theoretical verification. They used independently developed high-precision excited state potential energy surface construction methods and dynamic calculations of product quantum state resolution to accurately The phenomenon observed in the experiment was reproduced, revealing that highly excited sulfur dioxide molecules can produce oxygen products with high vibrational distribution through roaming reactions, while the traditional minimum energy path only produces oxygen products with low vibrational distribution.
The consistency between the experimental and theoretical results confirms the existence of highly excited state roaming reaction channels, indicating that roaming reactions are ubiquitous in chemical reactions.
Academician Yang Xueming pointed out that this research has brought new understanding to the previous theories of chemical reactions. Many phenomena that cannot be explained by traditional chemical reaction theories may be explained by the wandering reaction mechanism, which will enhance people's further understanding of the nature of chemical reactions. . Every breakthrough in basic research expands the boundaries of human cognition and expands human knowledge reserves.
A group photo of the scientific research team who "discovered the first example of a highly excited molecular roaming reaction channel". Dalian Institute of Chemistry, Chinese Academy of Sciences/Photo provided
The scientific research team of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, revealed that the next step will be to use the Dalian Coherent Light Source to carry out extreme ultraviolet photochemistry research on more molecules to gain a deeper understanding of the role of molecular photochemical processes in the evolution of molecules in the universe and the origin of life. At the same time, it will promote scientists to develop new Theoretical models and calculation methods enable more accurate description and prediction of chemical reactions. (over)