Reaction mechanism duality in O(1D2)+CD4-->OD+CD3 identified from scattering distributions of rotationally state selected CD3.

The scattering distributions of rotationally state-selected CD3 products in the O(1D2) reaction with deuterated methane at a collision energy of 5.6 kcal/mol were investigated. Markedly different features were found between the forward and backward scatterings of rovibrationally unexcited CD3, which provides the experimental evidence of the dual reaction mechanisms, i.e., insertion and abstraction on the ground- and excited-state potential energy surfaces, respectively, in this benchmark system. The gradual emergence of forward-backward symmetry in the angular distributions of CD3 in higher rotational states suggests that osculating complexes create rotationally hotter CD3.