Rotational-mode specific effects on the stereo-requirement in the reaction of prealigned-CHD3(v1 = 1; |JK = |10 or |1 ± 1) with the chlorine atom.

Several aspects of the stereo-specific requirement in the title reaction are systematically investigated in a crossed-beam experiment using a time-sliced, velocity-mapped imaging technique. Specifically, we explored (1) the differential steric effect from pre-aligning two different reagent rotational states and (2) the effect from probing different product rotational states. In the reaction with an aligned JK=10 reagent at Ec = 3.2 kcal mol-1, the head-on geometry yields a predominantly backward-scattered CD3(00) + HCl(v = 0) product pair, whereas the side-on approach results in a pronounced sideway-scattered distribution. The alternative CD3(00) + HCl(v = 1) channel exhibits a sharply forward-scattering feature for both the collisional geometries. The branching of the two product channels shows sensitive dependency on the collisional geometries. Probing different rotational states of CD3(00) reveals little variation in pair-correlated angular distributions, yet yields notable effect on the correlated vibrational branching of the HCl(v = 0, 1) coproducts. Similar steric propensities hold at lower collisional energy of 1.3 kcal mol-1. In stark contrast, diminishing steric effects were observed in the reaction with an aligned 1±1 reagent. Such huge differential, K-dependent stereo-requirements are largely attributed to the distinct "shapes" of the two rotational states of the aligned CHD3(v1 = 1) reagents.