Dalian Institute Of Chemical Physics Discovers The First Roaming Reaction Channel in Highly Excited State Of Molecules Using Dalian Coherent Light Station

In chemical reactions, diffuse reactions, as a special type of reaction mechanism, have attracted widespread attention from scientists. Dalian Institute of Chemical Physics, Chinese Academy of Sciences (hereinafter referred to as DICP) has discovered the first case of a roaming reaction channel in the highly excited state of a molecule by using the Dalian Coherent Light Source, which demonstrates the universality of the roaming reaction mechanism in chemical reactions, and provides a new perspective for understanding and predicting chemical reactions.
It is reported that this research result is completed by the experimental team of researcher Yuan Kaijun and academician Yang Xueming of Dalian Institute of Chemical Physics, together with the theoretical team of researcher Fu Bina and academician Zhang Donghui, and the results were published in the journal Science on February 16th, Beijing time.
The occurrence of chemical reactions is like "going over the mountain". In the traditional transition state theory of chemical reactions, the reaction mainly follows the path of minimum energy, just like a "mountain climber" usually finds the lowest ridgeline and crosses a high mountain in order to consume the least amount of energy. In some chemical reactions, the molecules may "circle away" from the periphery of the mountain peaks. From a microscopic point of view, the atoms or groups do not immediately break away from the molecules, but rather "hang around" near the molecules, far away and close to the molecules, just like astronauts "roaming" in space. "roaming", and eventually form a different product from the traditional chemical reaction, which is the roaming reaction.
At the beginning of the 21st century, scientists discovered roaming reaction for the first time. Since then, the analysis of the mechanism of diffuse reactions has been limited to the low-electronic and ground states of molecules. The emergence of the Dalian Coherent Light Source (DCLS) has solved the problem. The Dalian Coherent Light Source (DCLS) is China's first extreme ultraviolet free-electron laser developed by the team in collaboration with the Shanghai Institute of Applied Physics (SIAP), and is the world's only free-electron laser user device operating in the extreme ultraviolet wavelength band. By outputting high-brightness, wavelength-tunable extreme ultraviolet light from the Dalian Coherent Light Source, any molecule can be excited to a specific highly excited state.
The team of researcher Yuan Kaijun and academician Yang Xueming has been engaged in the research of molecular photochemical reactions for many years, and has always believed in the existence of roaming reactions of molecules in the highly excited state, "When developing the Dalian Coherent Light Source our team independently laid out several research directions in advance, and interstellar molecular photochemistry is one of them." Yuan Kaijun said, "It can be said that the Dalian Coherent Light Source opens the door to the study of molecular highly excited state reaction mechanism research."
The team used the Dalian Coherent Light Source to prepare highly excited state sulfur dioxide molecules, and combined with the self-developed high-resolution ion imaging technology to probe the quantum state distribution of excited state oxygen products. It was found that the excited state oxygen products generated by the dissociation of sulfur dioxide molecules near the 133 nm band showed two vibrational quantum state distributions.
Subsequently, the team of researcher Bina Fu and academician Donghui Zhang accurately reproduced the experimentally observed phenomenon by using the independently developed high-precision excited state potential energy surface construction method and kinetic calculations of product quantum state resolution, revealing that sulfur dioxide molecules in the high excited state can generate oxygen products with high vibrational dynamics distributions through the diffuse reaction, whereas the conventional minimum energy pathway only generates oxygen products with low vibrational dynamics distributions. The agreement between the experimental and theoretical results confirms the existence of the highly excited state diffuse reaction channel and shows that diffuse reactions are prevalent in chemical reactions.
"Through this study, we have generated a new perception of the previous theories of chemical reactions, and many phenomena unexplained by traditional chemical reaction theories can potentially be explained by the diffuse reaction mechanism, which will enhance further understanding of the nature of chemical reactions." Academician Yang Xueming said, "Every breakthrough in basic research expands the boundaries of human cognition and expands human knowledge reserves."