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.