Stereodynamic descriptions of molecular collisions concern the angular correlations that exist between vector properties of the motion of the participating species, including their velocities and rotational angular momenta. Measurements of vector correlations provide a unique view of the forces acting during collisions, and are a stringent test of electronic-structure calculations of molecular interactions. Here, we present direct measurement of the four-vector correlation between initial and final relative velocities and rotational angular momenta in a molecular collision. This property, which quantifies the extent to which a molecule retains a memory of its initial sense of rotation, or handedness, as a function of scattering angle, yields insight into the dynamics of a molecular collision. We report non-intuitive changes in the handedness for specific states and scattering angles, reproduced by classical and quantum scattering calculations. Comparison to calculations on different ab initio potential energy surfaces demonstrates this measurement’s exquisite sensitivity to the underlying intermolecular forces.

分子碰撞的立体动力学描述涉及参与物种运动的矢量特性之间存在的角度相关性，包括它们的速度和旋转角动量。矢量相关性的测量提供了碰撞过程中作用力的独特视图，并且是对分子相互作用的电子结构计算的严格测试。在这里，我们介绍分子碰撞中初始和最终相对速度与旋转角动量之间的四矢量相关性的直接测量。这种特性量化了分子保留其初始旋转或旋度感的程度，这是散射角的函数，可以洞悉分子碰撞的动力学。我们报告了特定状态和散射角在惯性上的非直观变化，这些变化是通过经典和量子散射计算得出的。与在不同的从头算势能面计算的比较表明，该测量对潜在的分子间力非常敏感。