Imaging the pair-correlated dynamics and isotope effects of the Cl+CH2D2 reaction

Abstract

By using a time-sliced (ion) velocity-imaging technique, the title reaction was investigated to interrogate the pair-correlated dynamics of HCl (DCl) in concomitance with the CHD(2) or CHD(2) ground-state product under the crossed-beam conditions. Product pair-correlated excitation functions, vibrational branching ratios, and angular distributions were obtained over a wide range of collision energies, from 2 to 22 kcal/mol. Two distinct reaction mechanisms were uncovered. Both the dominant ground-state reaction of Cl + CH(2)D(2)(v = 0) --> HCl(v = 0)/DCl(v = 0) + CHD(2)(0(0))/CH(2)D(0(0)) and the reaction forming the same product pairs from bend-excited CH(2)D(2) reactants proceed through direct mechanisms, which shift from a rebound dynamics near thresholds to a peripheral dynamics at higher E(c). Reactivity of forming the HCl(v = 1)/DCl(v = 1,2) + CHD(2)(0(0))/CH(2)D(0(0)) product pairs from ground-state reactants is small, yet shows dynamics pattern characteristics of a resonant reaction pathway. Significant spin-orbit reactivity of Cl(*)((2)P(1/2)) was discovered, and its mechanism appears to be also mediated by the resonant reaction pathway. Comparing the dynamical attributes of the H- and D-atom transfer channels, remarkable isotope effects are found-in line with the previous findings in the Cl + CH(4)/CD(4) and Cl + CHD(3) reactions.