Yang Tiangang, Huang Long, Xiao Chunlei, Chen Jun, Wang Tao, Dai Dongxu, Lique Francois, Alexander Millard H, Sun Zhigang, Zhang Dong H, Yang Xueming, Neumark Daniel M
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, China.
University of Chinese Academy of Sciences, Beijing, China.
Nat Chem. 2019 Aug;11(8):744-749. doi: 10.1038/s41557-019-0280-3. Epub 2019 Jun 24.
Chemical reactions are important in the evolution of low-temperature interstellar clouds, where the quantum tunnelling effect becomes significant. The F + para-H → HF + H reaction, which has a significant barrier of 1.8 kcal mol, is an important source of HF in interstellar clouds; however, the dynamics of this quantum-tunnelling-induced reactivity at low temperature is unknown. Here, we show that this quantum tunnelling is caused by a post-barrier resonance state. Quantum-state-resolved crossed-beam scattering measurements reveal that this resonance state has a collision energy of ~5 meV and a lifetime of ~80 fs, which are in excellent agreement with a recent anion photoelectron spectroscopic study. Accurate quantum reactive scattering calculations on the new iCSZ-LWAL potential energy surfaces provides a detailed explanation of the experimental results. The reaction rate for this system was also theoretically determined accurately at temperatures as low as 1 K.
化学反应在低温星际云中的演化过程中很重要，在那里量子隧穿效应变得显著。F + 对 - H → HF + H反应存在1.8千卡/摩尔的显著势垒，是星际云中HF的一个重要来源；然而，这种低温下量子隧穿诱导反应性的动力学尚不清楚。在这里，我们表明这种量子隧穿是由势垒后共振态引起的。量子态分辨交叉束散射测量表明，这种共振态的碰撞能量约为5毫电子伏特，寿命约为80飞秒，这与最近的阴离子光电子能谱研究结果非常吻合。在新的iCSZ - LWAL势能面上进行的精确量子反应散射计算为实验结果提供了详细解释。该系统的反应速率在低至1 K的温度下也通过理论精确确定。
