China News Service, Beijing, January 13 (Reporter Sun Zifa) In the face of ubiquitous chemical reactions, how to precisely control them is one of the core goals of chemical science research.
As human beings' understanding of chemical reactions continues to reach the level of atomic molecules and quantum states, how to further develop the principles and methods of precise control of chemical reactions at the microscopic level has also become a goal that scientists are striving for.
The latest news from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences (Dalian Institute of Chemical Physics, Chinese Academy of Sciences) said that the experimental team of academician Yang Xueming and researcher Xiao Chunlei, academician Zhang Donghui, and the theoretical team of associate researcher Zhang Zhaojun have made an important progress through a strong alliance. Control the direction of molecular chemical bonds to realize the precise regulation of the three-dimensional dynamics of chemical reactions.
This important chemical research paper was published in the internationally renowned academic journal Science on the morning of January 13th, Beijing time in the form of a research article. A milestone breakthrough in the field.
Researchers at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences work in front of a laser that controls the orientation of the chemical bonds of hydrogen molecules.
Photo provided by Dalian Institute of Chemical Physics, Chinese Academy of Sciences
The joint team of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences said that the essence of chemical reactions is the process in which microscopic particles such as atoms and molecules collide with each other and cause old chemical bonds to break and new chemical bonds to form.
Stereodynamic effects are a basic and important issue in chemical reactions, focusing on how the spatial orientation of reactant molecules affects the reaction process during collisions.
The root of the stereodynamic effect is that the reactant molecules are not simple particles, but have specific structures and shapes.
For example, a hydrogen molecule is formed by covalently bonding two hydrogen atoms, like a "dumbbell".
Therefore, when another reactant collides with the hydrogen molecule, it attacks from one end of the hydrogen molecule, or directly attacks the covalent bond of the hydrogen molecule, the reaction probability and the corresponding kinetic process of the two cases may show obvious difference.
For a long time, how to use the stereodynamic effect in chemical reactions to achieve fine control of the chemical reaction process and results has been one of the frontier issues in the study of chemical kinetics.
A hydrogen molecule is the simplest molecule, and it is a non-polar diatomic molecule, which does not easily change its orientation when approaching another molecule.
Therefore, elementary chemical reactions involving hydrogen molecules are ideal models for studying stereodynamic effects.
However, it has been difficult to experimentally prepare a sufficient number of hydrogen molecules with specific orientations to study the stereodynamic phenomena in related reactions.
In response to this challenge, the experimental team of Yang Xueming and Xiao Chunlei developed a high-energy, single longitudinal mode nanosecond pulsed optical parametric oscillator amplifier to realize the three-dimensional dynamic regulation of hydrogen molecules.
By manipulating the polarization direction of laser photons during stimulated Raman excitation, the team prepared hydrogen molecules in a specific vibration-rotational excited state in the molecular beam, and at the same time endowed the chemical bonds of hydrogen molecules with specific spatial orientations.
Under the collision energy of 0.50eV, the difference of the differential cross section of the H+HD→H2+H reaction between the two different collision configurations is very obvious.
Photo provided by Dalian Institute of Chemical Physics, Chinese Academy of Sciences
The experimental team further used the state-to-state resolution time-of-flight detection method of the Rydberg state of hydrogen atoms based on extreme ultraviolet laser technology, combined with crossed molecular beam technology, carefully measured the three collision energies of 0.50, 1.20, and 2.07 electron volts. , the results of the H+HD→H2+D reaction between two different configurations of hydrogen deuterium molecules (HD) and hydrogen (H) atoms, it is found that there are significant stereodynamic forces in the quantum state and scattering angle distribution of hydrogen molecules (H2) produced academic differences.
In order to understand the dynamic process, the theoretical team of Zhang Donghui and Zhang Zhaojun carried out non-adiabatic quantum dynamics simulation to accurately reproduce the phenomenon observed by the experimental team, and combined with the method of polarization differential cross section theory to analyze in detail the three-dimensional dynamics existing in the reaction The chemical effect reveals that the quantum interference phenomenon plays an important role in the vertical collision configuration reaction.
"The previous chemical reaction research may be like a 'blind box', which is determined by the original quantum properties, and researchers cannot control it at will. We can only extract the desired results with a certain probability." Zhang Donghui explained vividly , "But now we can excite a specific chemical bond and control its direction through precise control, and directly get the result we want."
The Dalian Institute of Chemical Physics of the Chinese Academy of Sciences stated that through high-precision experiments and theoretical research, the joint team of the Institute successfully verified that the chemical reaction can be finely regulated through the manipulation of the spatial orientation of the hydrogen molecular quantum state, which shows that human understanding and regulation of chemical reactions have reached a new height.
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