Nonadiabatic Photodissociation of the Hydroxymethyl Radical from the 2(2)A State. Surface Hopping Simulations Based on a Full Nine-Dimensional Representation of the 1,2,3(2)A Potential Energy Surfaces Coupled by Conical Intersections.

The nonadiabatic photodissociation CH2OH(1(2)A) + hv → CH2OH(2,3(2)A) → CH2O + H or HCOH(cis or trans) + H is addressed using trajectory surface hopping dynamics on a quasi-diabatic representation, H(d), of the 1,2,3(2)A coupled, adiabatic potential energy surfaces. We focus on dynamics originating on the 2(2)A potential energy surface. The H(d) is based exclusively on electronic structure data obtained from a multireference configuration interaction single and double excitation expansion, composed of over 67 million configuration state functions, and treats all nine internal degrees of freedom in an even-handed manner. Each simulation is based on bundles of 10000 trajectories randomly selected from harmonic Wigner distributions and propagated for up to 1 ps. The bimodal distribution in the kinetic energy release spectrum is explained in terms of direct versus quasi-statistical dissociation.