Observation of the geometric phase effect in the H + HD → H<sub>2</sub> + D reaction.

Yuan, Daofu; Guan, Yafu; Chen, Wentao; Zhao, Hailin; Yu, Shengrui; Luo, Chang; Tan, Yuxin; Xie, Ting et al. · Science · 2018

basic_science · Level V

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Abstract

Theory has established the importance of geometric phase (GP) effects in the adiabatic dynamics of molecular systems with a conical intersection connecting the ground- and excited-state potential energy surfaces, but direct observation of their manifestation in chemical reactions remains a major challenge. Here, we report a high-resolution crossed molecular beams study of the H + HD → H<sub>2</sub> + D reaction at a collision energy slightly above the conical intersection. Velocity map ion imaging revealed fast angular oscillations in product quantum state-resolved differential cross sections in the forward scattering direction for H<sub>2</sub> products at specific rovibrational levels. The experimental results agree with adiabatic quantum dynamical calculations only when the GP effect is included.