The collision dynamics between a pair of aligned molecules in the presence of a partial-wave resonance provide the most sensitive probe of the long-range anisotropic forces important to chemical reactions. Here we control the collision temperature and geometry to probe the dynamics of cold (1–3 K) rotationally inelastic scattering of a pair of optically state-prepared D₂ molecules. The collision temperature is manipulated by combining the gating action of laser state preparation and detection with the velocity dispersion of the molecular beam. When the bond axes of both molecules are aligned parallel to the collision velocity, the scattering rate drops by a factor of 3.5 as collision energies >2.1 K are removed, suggesting a geometry-dependent resonance. Partial-wave analysis of the measured angular distribution supports a shape resonance within the centrifugal barrier of the l = 2 incoming orbital. Our experiment illustrates the strong anisotropy of the quadrupole–quadrupole interaction that controls the dynamics of resonant scattering.

在存在部分波共振的情况下，一对排列的分子之间的碰撞动力学提供了对化学反应重要的长程各向异性力的最灵敏的探测。在这里，我们控制碰撞温度和几何形状以探测一对光学状态制备的 D _{2的冷 (1-3 K) 旋转非弹性散射动力学}分子。通过结合激光态制备和检测的门控作用与分子束的速度色散来控制碰撞温度。当两个分子的键轴平行于碰撞速度排列时，散射率下降 3.5 倍，因为碰撞能量 > 2.1 K 被移除，表明几何相关的共振。测量的角分布的分波分析支持l  = 2 进入轨道的离心势垒内的形状共振。我们的实验说明了控制共振散射动力学的四极-四极相互作用的强各向异性。