The Intricate Dynamics of the Si(³P) + OH(X²Π) Reaction

The dynamics of the Si(³P) + OH(X²Π) → SiO(X¹Σ⁺,v',j') + H(²S) reaction is investigated by means of the quasi-classical trajectory method on the electronic ground state X²A' potential energy surface in the 10^-2-1 eV collision energy range. Although the reaction involves the formation of a long-lived intermediate complex, a high probability for back-dissociation to the reactants is found because of inefficient intravibrational redistribution of energy among the complex modes. At low collision energies, the reactive events are governed by a dynamics with mixed direct/indirect features. As the collision energy increases, the intermediate complex lifetime increases and final state distributions are found to be in reasonable agreement with statistical predictions obtained using the mean potential phase space theory, thus highlighting the indirect character of the process. These rich and puzzling dynamical features are in line with what has been previously observed for the S(³P) + OH(X²Π) reaction.