Pair-Correlated Imaging of Cl + CH3D(v4, v1-I, v1-II = 1, |jK⟩) → CH2D(vi) + HCl(v).

Abstract

The title reactions were studied at a collisional energy of 10.0 kcal mol-1 in a crossed-beam, product-imaging experiment. In terms of integral cross sections, all three CH3-stretching excited CH3D(vCH3 = 1) reagents promote the reactivity in forming the predominant product pair of (vCH2D, vHCl)s = (00, 0/1)s with a prominent mode-propensity of v4 > v1-I > v1-II, where v4 denotes the degenerate mode of CH3 asymmetric stretch and v1-I and v1-II are a pair of Fermi-coupled, symmetric-stretch states. The vibrationally excited CH2D product pairs of (61, 0)s, (11, 0)s, and (31, 0)s appear to be minor channels and display a reverse propensity of v4 < v1-I ≈ v1-II for (61, 0)s, while v4 > v1-I for (11, 0)s. Based on the observed angular distributions, we conjecture that, irrespective of the initial mode of excitation, the (00, 0)s product pair proceeds by a direct abstraction of the peripheral type, whereas the (00,1)s pair is mediated via a resonance pathway. Intriguingly, the angular distributions of the excited product pairs-(61, 0)s, (11, 0)s, and (31, 0)s-are remarkably similar and comprise the traits of both the peripheral mechanism and resonance pathway. Possible interpretation and implication are suggested. In addition, due to the spectral overlap of the REMPI bands and heavily congested image features, a robust data analysis method is developed, which enables us to extract the dynamics attributes of a weak feature buried in the proximate, more intense ones with high fidelity.