A milestone breakthrough! Chinese scientists have achieved precise regulation of the stereokinetics of chemical reactions

The direction of the chemical bond of the HD molecule is controlled with a laser so that it collides
with the H atom in two configurations.
Photo courtesy of Dalian Institute of Chemicals, Chinese Academy of Sciences

Beijing, Jan.
13 (Zhongxin Net) -- In the face of ubiquitous chemical reactions, how to precisely regulate is one of the core goals of
chemical science research.
As human understanding of chemical reactions continues to deepen to the atomic and molecular scale and quantum state level, how to further develop the principles and methods of precise regulation of chemical reactions at the microscopic level has also become the goal
of scientists.

The latest news from the Dalian Institute of Chemical Physics of the 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 of the institute, together with the theoretical team of academician Zhang Donghui and associate researcher Zhang Zhaojun, made an important progress by controlling the direction of molecular chemical bonds to achieve precise regulation
of the stereokinetics of chemical reactions.

This important chemical research result paper was published in the form of a research article in the internationally renowned academic journal Science on the morning of January 13, Beijing time, and the reviewers spoke highly that the research results were a milestone breakthrough
in the field of reaction kinetics.

Researchers at the Dalian Institute of Chemicals, Chinese Academy of Sciences, work
in front of a laser that controls the chemical bond orientation of hydrogen molecules.
Photo courtesy of Dalian Institute of Chemicals, Chinese Academy of Sciences

The joint team of the Dalian Institute of Chemicals of the Chinese Academy of Sciences said that the essence of chemical reactions is the process
of microscopic particles such as atoms and molecules colliding with each other and causing the breaking of old chemical bonds and the formation of new chemical bonds.
Stereokinetic effects are a fundamental and important issue in chemical reactions, focusing on how the spatial orientation of reactant molecules affects the reaction process during collision
.
The root cause of the stereokinetic effect is that reactant molecules are not simple particles, but have specific structures and shapes
.

For example, a hydrogen molecule is formed by two hydrogen atoms linked by a covalent bond, like a "dumbbell"
.
Therefore, when another reactant collides with a hydrogen molecule, it attacks from one end of the hydrogen molecule or directly attacks the covalent bond of the hydrogen molecule, and the reaction probability and corresponding kinetic process of the two cases may show a clear difference
.
For a long time, how to use the stereokinetic effect in chemical reactions to achieve fine control of chemical reaction processes and results is one of
the frontier issues in chemical kinetics research.

The hydrogen molecule is the simplest molecule, and it is a non-polar diatomic molecule, which is not prone to changes
in orientation in the process of approaching another molecule.
Therefore, the basic chemical reactions involving hydrogen molecules are ideal models
for studying stereokinetic effects.
However, it has been difficult to experimentally prepare a sufficient number of hydrogen molecules with a specific orientation, so it is impossible to study the stereokinetic 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 oscillation amplifier to realize the stereodynamic 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-to-excited state in the molecular beam, while giving specific spatial orientation to the chemical bonds of hydrogen molecules
.

At 0.
50eV collision energy, the differential reaction cross-sections of H+HD→H2+H reactions of two different collision configurations are very different
.
Photo courtesy of Dalian Institute of Chemicals, Chinese Academy of Sciences

The experimental team further used the state-state resolution hydrogen atom Rydberg state time-of-flight spectroscopy detection method based on extreme ultraviolet laser technology, combined with cross-molecular beam technology, and carefully measured the H+HD→H2+D reaction results of two hydrogen deuterium molecules (HD) and hydrogen (H) atoms of different configurations under the three collision energies of 0.
50, 1.
20 and 2.
07 electron volts, and found that there were significant stereodynamic differences in the quantum state and scattering angle distribution of the produced hydrogen molecule (H2).

。

In order to understand the dynamic process, the theoretical team of Zhang Donghui and Zhang Zhaojun carried out non-adiabatic dynamic simulation, accurately reproduced the phenomenon observed by the experimental team, and combined with the polarimetric differential cross-section theory method, analyzed the stereodynamic effects in the reaction in detail, revealing that quantum interference phenomena play an important role
in vertical collision configuration reactions.

"Previous chemical reaction research may be like a 'blind box', which is determined by the original quantum properties, researchers cannot control it casually, we can only have a certain probability of extracting the desired results
.
" Zhang Donghui explained, "But now we can directly get the results
we want by precise control, excitation of specific chemical bonds and control its direction.
" ”

According to the Dalian Institute of Chemistry of the Chinese Academy of Sciences, the joint team of the institute successfully verified that through the manipulation of the spatial orientation of the quantum state of hydrogen molecules, chemical reactions can be finely regulated through high-precision experiments and theoretical research, which indicates that human understanding and regulation of chemical reactions have reached a new height
.
(End)