Non-intuitive rotational reorientation in collisions of NO(A ²Σ⁺) with Ne from direct measurement of a four-vector correlation

Stereodynamic descriptions of molecular collisions concern the angular correlations which 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 a stringent test of electronic structure calculations of molecular interactions. In this work, we present the first 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 unprecedented insight into the dynamics of a molecular collision. We report surprising 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.