中文摘要：

玻恩-奥本海默近似是量子化学以及化学动力学理论研究的重要基石之一，它对于化学反应过程中的动力学非常重要。但是在Cl＋H2反应中该近似的适用性一直以来备受争议。本研究利用高灵敏度的交叉分子束实验，对Cl／／Cl^＊＋H2反应进行了交叉分子束反应散射的实验研究。实验结果表明激发态Cl‘原子的反应性在低碰撞能下与基态的C1原子的反应性相当，说明玻恩-奥本海默近似在低能时的适用性存在问题。但是，随着碰撞能量的增加，相对于基态C1原子，Cl^＊原子与H2的反应快速下降，这表明在Cl＋H2这一反应中玻恩-奥本海默近似在高碰撞能时是适用的。这一结果得到精确动力学理论研究的证实，而且解决了一个长期有争议的重要科学问题。

英文摘要：

The Born-Oppenheimer Approximation is the keystone to quantum chemistry and chemical dynamics. This approximation, also called adiabatic approximation, enables us to picture molecules as a set of nuclei moving over a potential energy surface. In this work, crossed molecular beam scattering experiment on the CI/CI＊ ＋ H2 reaction was carried out, based on hydrogen-atom Rydberg tagging detection technique, the ex perimental results reveal that even though CI＊ ＋ H2 is almost equally important to C1 ＋ H2 at low collision energy, suggesting the B-O approximation cannot be ap- plied at low collision energy. As collision energy increases, the CI＊ reaction becomes relatively much smaller relative the C1 reaction, implying that the B-O approximation works at higher collision energy. These results are in excellent agreement with fully quantum-reactive scattering calculations. This study resolves a longstanding disagreement between theory and experiment and confirms our ability to simulate accurately chemical reactions on multiple potential energy surfaces.