We show that collisions in a single supersonic molecular beam reach characteristic temperatures in the range of a few Kelvin. Experiments have been carried out for mixtures of H₂ and HD as well as HD and D₂ in a pulsed supersonic expansion. From the measured time-of-flight spectrum, we find that the high velocity edge of the distribution for both species is nearly coincident, but the average speed of the heavier species is slightly greater than the lighter one. By working in the few Kelvin regime, this relatively simple technique reduces the number of partial waves in the collision process, which allows the observation of collision resonances. Additionally, copropagation of scattering partners in a single molecular beam precisely defines the direction of their relative velocity vector, which is essential for the study of stereodynamics.

我们表明，单个超音速分子束中的碰撞达到了几个开尔文范围内的特征温度。已经对H ₂和HD以及HD和D _2的混合物进行了实验在脉冲超音速膨胀中。从测得的飞行时间频谱中，我们发现两种物种的高速分布边缘几乎重合，但是较重物种的平均速度略大于较轻物种的平均速度。通过在少数开尔文状态下工作，这种相对简单的技术减少了碰撞过程中分波的数量，从而可以观察到碰撞共振。此外，单个分子束中的散射伙伴的共传播精确地定义了它们的相对速度矢量的方向，这对于立体动力学的研究是必不可少的。