Accurate measurements of product state-resolved angular distributions are central to fundamental studies of chemical reaction dynamics. Yet, fine quantum-mechanical structures in product angular distributions of a reactive scattering process, such as the fast oscillations in the forward-scattering direction, have never been observed experimentally and the nature of these oscillations has not been fully explored. Here we report the crossed-molecular-beam experimental observation of these fast forward-scattering oscillations in the product angular distribution of the benchmark chemical reaction, H + HD → H₂ + D. Clear oscillatory structures are observed for the H₂(v′ = 0, j′ = 1, 3) product states at a collision energy of 1.35 eV, in excellent agreement with the quantum-mechanical dynamics calculations. Our analysis reveals that the oscillatory forward-scattering components are mainly contributed by the total angular momentum J around 28. The partial waves and impact parameters responsible for the forward scatterings are also determined from these observed oscillations, providing crucial dynamics information on the transient reaction process.

准确测量产物状态分辨的角分布对于化学反应动力学的基础研究至关重要。然而，在反应性散射过​​程的产物角分布中的精细量子力学结构，例如在前向散射方向上的快速振荡，从未在实验上被观察到，并且这些振荡的性质尚未得到充分的探索。在这里，我们报告了在基准化学反应的产物角分布H + HD→H ₂  + D中这些快速前向散射振荡的交叉分子束实验观察。观察到H ₂（v ' = 0，j′= 1，3）乘积状态的碰撞能量为1.35 eV，与量子力学动力学计算非常吻合。我们的分析表明，振荡前向散射分量主要是由大约28的总角动量J贡献的。负责前向散射的分波和冲击参数也由这些观察到的振荡确定，从而提供了有关瞬态反应过程的重要动力学信息。 。