Stereodynamical control of the H+HD→H2+D reaction through HD reagent alignment

Prealigning nonpolar reacting molecules leads to large stereodynamical effects because of their weak steering interaction en route to the reaction barrier. However, experimental limitations in preparing aligned molecules efficiently have hindered the investigation of steric effects in bimolecular reactions involving hydrogen. Here we report a high-resolution crossed-beam study of the reaction H+HD(ν=1, j=2)→H2(ν', j')+D at collision energies of 0.50, 1.20, and 2.07 electron volts, in which the vibrationally excited hydrogen deuteride(HD) molecules were prepared in two collision configurations, with their bond, preferentially aligned parallel and perpendicular to the relative velocity of collision partners. Notable stereodynamical effects in differential cross-sections were observed. Quantum dynamics calculations revealed that strong constructive interference in the perpendicular configuration plays an important role in the stereodynamical effects observed., ,对非极性反应分子实施预排列，可引发显著的立体动力学效应(stereodynamical effects)，这是由于在其抵达反应势垒(reaction barrier)的过程中，分子间存在较弱的导向相互作用。然而，受限于高效制备排列分子的实验瓶颈，学界针对含氢双分子反应空间效应的研究长期受阻。本研究针对碰撞能分别为0.50、1.20与2.07电子伏特的反应H+HD(ν=1, j=2)→H2(ν', j')+D开展了高分辨交叉分子束(high-resolution crossed-beam)实验：将振动激发态氘化氢(HD)分子制备为两种碰撞构型，使其化学键优先平行或垂直于碰撞双方的相对速度方向。实验观测到微分截面(differential cross-sections)中存在显著的立体动力学效应。量子动力学计算(quantum dynamics calculations)结果表明，垂直构型下的强相长干涉(constructive interference)是本次观测到的立体动力学效应的重要成因。