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Crossed Beam Experiment on the Validity of Born-Oppenheimer Approximation in Cl(2P)+D2→DCl+D Reaction
Yu-run Xie1,2,3,4, Yu-feng Wang2,4, Wei Wang2,4, Tao Wang5, Dong-xu Dai2, Chun-lei Xiao*2, Xue-ming Yang*2,5
1.Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China;2.State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China;3.School of Physical Science & Technology, ShanghaiTech University, Shanghai 201210, China;4.University of Chinese Academy of Sciences, Beijing 100049, China;5.College of Science, Southern University of Science and Technology, Shenzhen 518055, China
Abstract:
The reaction of chlorine atom Cl(2P) (Cl(2P3/2) and Cl*(2P1/2)) with D2 was investigated at collision energy from 4.5 kcal/mol to 6.5 kcal/mol with a high-resolution crossed molecular beam apparatus using the technique of D-atom Rydberg tagging detection. The contribution from the spin-orbit excited reaction Cl*(2P1/2)+D2, which is prohibited by Born-Oppenheimer (BO) approximation, was observed. Collision-energy dependence of differential cross sections (DCSs) near the backward scattering direction was measured. The BOforbidden reaction Cl*+D2 was found to be dominant at lower collision energy. As collision energy increases, reactivity of BO-allowed reaction Cl+D2 increases much faster than that of BO-forbidden reaction and becomes dominant at higher collision energy. Our experiment indicates that the additional energy of spin-orbit excitation in Cl* facilitates BO-forbidden reaction to pass through the barrier at lower collision energy, while BO approximation is still valid at collision energy near and above the reaction barrier. This tendency of reactivity of Cl/Cl*+D2 is similar to the isotopic reaction of Cl/Cl*+H2.
Key words:  Spin-orbit state, Born-Oppenheimer approximation, Crossed beam experiment
FundProject:
附件
Cl(2P)+D2→DCl+D反应中波恩-奥本海默近似有效性的交叉分子束研究
谢雨润1,2,3,4, 王玉奉2,4, 王 威2,4, 汪 涛5, 戴东旭2, 肖春雷*2, 杨学明*2,5
1.中国科学院上海高等研究院,上海 201210;2.中国科学院大连化学物理研究所,分子反应动力学国家重点实验室,大连 116023;3.上海科技大学物质科学与技术学院,上海 201210;4.中国科学院大学,北京 100049;5.南方科技大学理学院,深圳 518055
摘要:
本文利用高分辨的里德堡态氘原子标识-交叉分子束装置,研究了碰撞能为4.5∽6.5 kcal/mol范围内Cl(2P)[Cl(2P3/2)和Cl*(2P1/2)]与D2的反应. 虽然自旋轨道激发态反应Cl*(2P1/2)+D2在波恩-奥本海默(B-O)近似下本应是禁阻的,但实验中观测到了该反应的贡献. 通过测量靠近后向的碰撞能相关的微分散射截面连线,发现低碰撞能下的产物主要来自于B-O近似禁阻的反应Cl*+D2. 随着碰撞能的提高,自旋轨道基态反应Cl+D2的反应性增加明显要比自旋轨道激发态反应Cl*+D2更快,并且在高碰撞能下成为产物的主要来源. 实验结果表明:在低碰撞能下,Cl*中自旋轨道激发态的额外能量,可以帮助B-O近似禁阻的反应Cl*+D2越过势垒;然而当碰撞能接近和高于反应势垒时,B-O近似允许的反应Cl+D2占主导地位. Cl/Cl*+D2反应中B-O近似有效性的特征与其同位素反应Cl/Cl*+H2是一致的.
关键词:  自旋轨道态,波恩-奥本海默近似,交叉束实验
DOI:10.1063/1674-0068/cjcp1912221
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