Global 1 1A" potential energy surface of CH2 and quantum dynamics of a sideways insertion mechanism for the C(1D)+H2→CH(2Π)+H reaction

A global adiabatic potential energy surface ( PES) corresponding to the second singlet state 1 (1)A '' ( 1 B-1(1)) of CH2 has been computed in a similar way as the. rst singlet state 1 (1)A' in our previous work [ B. Bussery-Honvault et al., J. Chem. Phys., 2001, 115, 10 701]. This PES has a calculated well depth of 79.9 kcal mol(-1) relative to the C(D-1) + H-2 asymptote and correlates to CH((2)Pi) + H. It presents large barriers in the C(D-1) + H-2 arrangement for both collinear and perpendicular geometries but no barrier for geometries about 60 degrees and leads to a sideways insertion mechanism for the reaction C(D-1) + H-2 --> CH((2)Pi) + H. The ab initio calculations were carried out for 4644 geometries and the resulting energies were fitted to a many-body expansion. Accurate three-dimensional quantum mechanical scattering calculations have been performed for the C(D-1) + H-2( v = 0, j = 0) reaction on this ab initio 1 (1)A '' PES in the collision energy range [0 - 11.5 kcal mol(-1)]. The J = 0 reaction probabilities show dense resonance structures as those obtained with the 1 (1)A' PES. However some different dynamical features have been found.