The effect of a conical intersection on cross sections for collision-induced dissociation

The cross section for H + H₂(v, j) → 3H, where v and j denote selected vibrational and rotational quantum numbers, is calculated by the quasiclassical trajectory method, using trajectory surface hopping to include the effect of the first excited electronic state which has a conical intersection with the ground state. The excited electronic state allows for collision-induced dissociation by the process H + H₂(X ¹Σ_g⁺) → H₃(1 ²A′) → H₃(2 ²A′) → H + H₂(b ³Σ_u⁺) → 3H, where the various transitions all occur in the course of a single collision. This new surface hopping mechanism increases the cross sections and rate constants for production of unbound states by 2%-44% for the conditions examined.